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1.  The Association of Neonatal Dacryocystoceles and Infantile Dacryocystitis with Nasolacrimal Duct Cysts (An American Ophthalmological Society Thesis) 
To investigate whether neonatal dacryocystoceles and dacryocystitis are associated with nasolacrimal duct cysts, and to report the outcomes of treatment of these disorders.
This was a retrospective medical record review of two groups of infants with nasolacrimal duct (NLD) obstruction. The first group had dacryocystoceles with or without dacryocystitis. The second group had NLD obstruction with symptoms severe enough to require early NLD probing. All of the patients underwent NLD probing and nasal endoscopy. When present, NLD cysts were removed.
In the first group, 33 infants had dacryocystoceles. Acute dacryocystitis was present in 16 patients, 12 had noninfected dacryocystoceles that did not resolve, and 5 had dacryocystoceles that resolved but severe symptoms persisted. All of the patients had NLD cysts that were surgically removed. The symptoms resolved after surgery in 31 patients (94%). In the second group, 27 infants less than 6 months old without dacryocystoceles underwent early NLD probing and endoscopy due to severity of symptoms. Twelve (44%) of these patients had NLD cysts. The symptoms resolved in 11 (92%) of 12 patients following NLD probing and cyst removal.
Neonatal dacryocystoceles are almost always associated with NLD cysts. The success rate of NLD probing and endoscopic cyst removal in these patients is excellent. Nasolacrimal duct cysts also are present in many young infants with severe symptoms of NLD obstruction. Nasal endoscopy is an important adjunct to the management of these infants.
PMCID: PMC3671363  PMID: 23818736
2.  Uncommon Presentation of Congenital Lacrimal Duct Obstruction A Case Report of Congenital Amniontocele 
Oman Medical Journal  2007;22(3):60-61.
Congenital amniontocele also known as congenital dacryocystocele is an uncommon variant of a very common condition (Naso-Lacrimal Duct Obstruction, NLDO) that affects newborn babies. The congenital amniontocele causes obstruction of the lacrimal drainage system creating a cystic swelling of the lacrimal sac. It usually presents at birth or soon after birth, as a bluish swelling, below and nasal to the medial canthus. If the congenital amniontocele is associated with intranasal cystic swelling of the NLD and if it is large and bilateral it can cause severe respiratory distress particularly during milk feeding.
We report a case of 24 days old female newborn baby who were presented to us from pediatric clinic of Rustaq Hospital with bluish cystic swelling below the left medial canthus soon after the birth.
Congenital amniontocele is relatively rare and the literature describes a variable natural course of these lesions with resultant controversy in their management. Usually congenital amniontocele resolves spontaneously with conservative management, and if not, dacryocystitis might develop. Treatment of congenital amniontocele comprises digital sac massaging and early probing the lacrimal system,8 or some times, intranasal surgery in the form of marsupialization of the intranasal cyst, this is usually performed endoscopically.7 We report successful conservative management in our case and recommend this with oral and topical antibiotics with lacrimal sac massage for 7 to 10 days and, if there is no response, to consider surgical intervention in the form of lacrimal probing.
PMCID: PMC3294153  PMID: 22400096
Congenital amniontocele; dacryocystocele; lacrimal probing; antibiotics; conservative
3.  Preventing Silicone Tube Extrusion after Nasolacrimal Duct Intubation in Children 
Herein we report our experience with a simple technique for reducing the rate of silicone tube extrusion after nasolacrimal duct (NLD) intubation for congenital NLD obstruction. Medical records of children older than 2 years, with or without history of failed probing, who had undergone NLD intubation with a Crawford silicone tube over a period of 4 years were reviewed. In all subjects, one end of the Crawford tube was passed through a piece of scalp vein tubing followed by applying one or two knots. All Crawford tubes were removed after 3 months. Main outcome measures included complications such as tube extrusion, nasal discharge, crust formation and pyogenic granuloma formation. Fifty-seven patients, including 49 unilateral and 8 bilateral cases with mean age of 3.8±1.6 (range, 2 to 11.5) years were operated. No complications such as tube dislodgement, significant nasal discharge, crust or pyogenic granuloma formation occurred prior to Crawford tube removal. All silicone tubes were successfully removed from the nasal cavity. In conclusion, passing one end of the Crawford tube through a small piece of scalp vein tubing before knotting it in the nasal cavity seems to decrease the rate of tube extrusion which is the most common complication following NLD intubation in children.
PMCID: PMC3381084  PMID: 22737375
Nasolacrimal Duct Intubation; Silicone Tube Extrusion; Crawford Tube; Nasolacrimal Duct Obstruction
4.  Development of the Lacrimal Apparatus in the Rabbit (Oryctolagus cuniculus) and Its Potential Role as an Animal Model for Humans 
Anatomy Research International  2011;2011:623186.
Rabbits have been proposed as a model organism for the human lacrimal apparatus (LA), including the nasolacrimal duct (NLD), based principally on comparative studies of adult morphology; however, little is known about its development. The NLD first appears as an incomplete primordium in the subcutaneous region of the primordial eyelid and subsequently elongates to reach the naris. One posterior and three anterior orbital glands are present fetally although one of the anterior glands is soon lost. The NLD follows a tortuous path and passes through a bony canal consisting of lacrimal, maxilla, and maxilloturbinal bones at different regions. Although early developmental similarities exist to haplorhine primates, the narial opening of the NLD resembles strepsirrhines. This distinction, along with the ductal and glandular differences at the orbital end of the NLD, indicates that rabbits may be a poor model for LA drainage in primates, specifically humans.
PMCID: PMC3335492  PMID: 22567296
5.  Prevalence of amblyopia in children undergoing nasolacrimal duct irrigation and probing 
Indian Journal of Ophthalmology  2013;61(12):698-700.
To investigate ambylopia and amblyopia risk factors of children who underwent nasolacrimal duct (NLD) irrigation and probing for congenital nasolacrimal duct obstruction (CNLDO).
Materials and Methods:
The medical records of patients who had undergone NLD irrigation and probing for CNLDO at an age of 3 years or younger were reviewed, and 51 of the patients were recalled between October 1 and December 31, 2011 for a detailed ophthalmic examination to determinate amblyopia or amblyopia risk factors. Amblyopia was accepted as difference in visual acuity of two or more Snellen lines between the two eyes or visual acuity of 20/30 or worse in either eye.
The median age of the 51 patients to whom NLD irrigation and probing were attempted for CNLDO was 23 months. CNLDO affected a total of 70 eyes. All patients were reviewed for best-corrected visual acuity, refractive errors, and strabismus at a median age of 70.5 months (range 31-95 months). Amblyopia or amblyopia risk factors were identified in 14 patients (27.5%). One child (7.15%) had only strabismus, six children (42.8%) had only amblyogenic refractive errors, two (14.3%) had a combination of two, one child (7.15%) had a family history for amblyopia, but four children (28.6%) had no amblyopia risk factors but had amblyopia.
Amblyogenic risk factors are found higher in patients with CNLDO and patients undergoing NLD irrigation and probing in comparison to normal population. Therefore, we recommend these children to routinely undergo cycloplegic refractions and full ophthalmic examinations.
PMCID: PMC3917385  PMID: 24413822
Amblyopia; nasolacrimal duct obstruction; probing
6.  A Case of Recurrent Schneiderian Papilloma of the Lacrimal Sac Invading the Nasal Cavity 
A 44-year-old man presented with a history of chronic epiphora, discharge from the right eye, and a palpable mass in the medial canthal area. Irrigation of the lacrimal system revealed bloody discharge. Orbital magnetic resonance imaging (MRI) showed a well-defined heterogeneous enhanced mass filling the lacrimal sac and upper nasolacrimal duct (NLD). A wide excision and surgical biopsy were performed. Histopathology showed the tumor to be an exophytic Schneiderian papilloma with moderate to severe dysplasia. Three months later, the mass was found to be invading the nasal cavity through the NLD. Endoscopic histopathological evaluation confirmed that it was identical to the originally identified papilloma.
PMCID: PMC2694284  PMID: 19568358
Lacrimal sac; Recurrent exophytic papilloma; Schneiderian papilloma
7.  Plasmacytoma of the Nasolacrimal Duct Simulating Dacryocystitis: An Uncommon Presentation for Extramedullary Relapse of Multiple Myeloma 
Case Reports in Oncology  2012;5(1):119-124.
The most common site for localized forms of plasma cell neoplasms (extramedullary plasmacytoma; EMP) is the upper respiratory tract, including the oropharynx, nasal cavities, sinuses and larynx. A 50-year-old woman with a history of myeloma in complete remission after autologous stem cell transplantation complained of two weeks of epiphora of the left eye with subsequent diplopia, bloody nasal discharge and progressive swelling around the nasolacrimal sac. A solitary mass in the left sinonasal area, extending to the nasolacrimal duct (NLD) was detected on MRI, whose histopathological examination was consistent with plasmacytoma. Further clinical investigation ruled out multiple myeloma (MM). The patient underwent debulking surgery and adjuvant chemotherapy followed by local radiotherapy in an attempt to achieve complete response. Despite being a rare entity, EMP of the NLD should be considered in the differential diagnosis of epiphora and dacryocystitis. To our knowledge, this is the first case of a plasmacytoma of the NLD presenting as isolated extramedullary relapse of MM. The follow-up in EMPs should include appropriate imaging studies, a systemic workup to rule out MM.
PMCID: PMC3364047  PMID: 22666199
Dacryocystitis; Multiple myeloma; Nasolacrimal duct; Plasmacytoma
8.  Prenatal early diagnosis of dacryocystocele, a case report and review of literature 
Dacryocystocele (mucocele, amniocele) is a relatively rare variant of nasolacrimal duct obstruction which refers to the cystic dilatation of lacrimal pathway above and below the lacrimal sac. It is a benign pathology and can be treated successfully after birth, but its prenatal detection is important, because it may be seen in numerous syndromes and may serve as their marker. Bilateral cysts have the possibility for intranasal extension and an obstruction to the nasal passages may result in neonatal respiratory distress requiring surgical intervention Unilateral cases are important for the differential diagnosis with serious facial abnormalities. We present a case of early prenatal detection of a 28 year-old G: 1 P: 0 pregnant woman with bilateral dacryocystocele. She presented a live, normally developed singleton fetus on sonographic examination at 12, 16 and 22 weeks. At 25th weeks, we diagnosed a hypoechogenic mass, that was situated inferomedially to the eyes in the fetal face with 2 and 3-D ultrasound. A 3850-g live female infant was delivered by Cesarean section due to breech presentation at 39 weeks following preterm rupture of membranes. We report the case with intranasal components studied during fetal life by 2 and 3-D ultrasound and magnetic resonance (MR) imaging.
PMCID: PMC3939260  PMID: 24592005
Dacryocystocele; mucocele; amniocele; magnetic resonance imaging; nasolacrimal duct cyst
9.  Value of microbiology study in congenital nasolacrimal duct obstruction 
Saudi Journal of Ophthalmology  2012;26(2):223-228.
Evaluation of the effect of different microorganisms on congenital nasolacrimal duct obstruction (CNLDO) tightness and whether probing or silastic intubation is likely to fail in a particular microorganism infection.
The culture and sensitivity results of lacrimal drainage system (LDS) discharge samples from patients with CNLDO were reviewed. Different microorganisms were correlated with the severity of nasolacrimal duct (NLD) obstruction observed during surgical intervention. The success rates of probing and silastic intubation as a primary procedure for each identifiable microorganism were documented. Statistical analysis was conducted to correlate the type of microorganism with the tightness of CNLDO and treatment failure.
Out of 181 specimens, 22 had no growth (12.1%). LDS with positive culture had 76.6% successful probing (n = 49) and 82.1% successful silastic intubation (n = 78). Gram-positive and Gram-negative species were almost equally detected. The most prevalent organisms were Streptococcus pneumoniae and Hemophilus influenzae (48.1% and 39.2%, respectively). Tight CNLDO was more prevalent in Serratia marcescens (n = 2; 100%) and Staphylococcus aureus (n = 4; 33.3%) infections with a 7.75 Odds ratio [95% confidence interval (CI), 1.67–34.63]. Staphylococcus aureus had 37.5% successful probing; however, success was achieved in all cases with silastic intubation. Serratia marcescens infections had 100% successful silastic intubation.
Microbiology study can predict tight CNLDO and helps in choosing the most successful treatment option. CNLDO with Staphylococcus infection and Serratia marcescens were likely to have tight NLD obstruction and silastic intubation had better outcomes.
PMCID: PMC3729323  PMID: 23960996
Microbiology; Congenital; Nasolacrimal duct; Obstruction
10.  A rare cause of nasolacrimal duct obstruction: Dentigerous cyst in the maxillary sinus 
Indian Journal of Ophthalmology  2009;57(6):465-467.
The most common abnormality of the lacrimal drainage system is congenital or acquired nasolacrimal duct obstruction. The causes of acquired nasolacrimal duct obstruction may be primary or secondary. The secondary acquired obstructions may result from infection, inflammation, neoplasm, trauma or mechanical causes. The maxillary sinus cysts usually obstruct the nasolacrimal duct mechanically. Dentigerous cysts are one of the main types of maxillary cysts. These cysts are benign odontogenic cysts which are associated with the crowns of unerupted teeth. The clinical documentations of mechanical nasolacrimal duct obstructions due to a dentigerous cyst in the maxillary sinus are very rare in literature. In this case report, we describe a dentigerous cyst with a supernumerary tooth in the maxillary sinus in an 11-year-old male child causing an obstruction to the nasolacrimal duct. The case was successfully managed surgically by Caldwell Luc approach.
PMCID: PMC2812769  PMID: 19861752
Caldwell Luc approach; dentigerous cyst; nasolacrimal duct
11.  Nasolacrimal Duct Closure Modulates Ocular Mucosal and Systemic CD4+ T-Cell Responses Induced following Topical Ocular or Intranasal Immunization ▿  
Both topical ocular and topical intranasal immunizations have been reported to stimulate the ocular mucosal immune system (OMIS) and the systemic immune system. Nasolacrimal ducts (NLDs) are the connecting bridges between the OMIS and nasal cavity-associated lymphoid tissue (NALT). These ducts drain topical ocularly administrated solutions into the inferior meatus of the nose to reach the NALT. Inversely, NLDs also drain intranasally administrated solutions to the mucosal surface of the eye and thus the OMIS. This unique anatomical connection between the OMIS and NALT systems provoked us to test whether the OMIS and NALT are immunologically interdependent. In this report, we show that both topical ocular administration and topical intranasal administration of a mixture of immunodominant CD4+ T-cell epitope peptides from herpes simplex virus type 1 (HSV-1) glycoprotein D (gD) emulsified with the CpG2007 mucosal adjuvant are capable of inducing local (in conjunctiva) as well as systemic (in spleen) HSV-peptide-specific CD4+ T-cell responses. Interestingly, surgical closure of NLDs did not significantly alter local ocular mucosal CD4+ T-cell responses induced following topical ocular immunization but did significantly enhance systemic CD4+ T-cell responses (as measured by both T-cell proliferation and gamma interferon (IFN-γ) production; P < 0.005). In contrast, NLD closure significantly decreased ocular mucosal, but not systemic, CD4+ T-cell responses following intranasal administration of the same vaccine solution (P < 0.001). The study suggests that NALT and the OMIS are immunologically interconnected.
PMCID: PMC2837957  PMID: 20089796
12.  Bilateral Congenital Lacrimal Fistula in Down Syndrome 
Congenital lacrimal fistulae are rare in Down syndrome and bilateral presentation is very unusual. It can be associated with nasolacrimal duct obstruction. We report a 3-year-old female with Down syndrome who presented with watering and discharge from both eyes and bilateral fistulous openings present inferonasal to the medial canthus. Upon examination, the lacrimal sac regurgitation test was positive on both sides. Our case report documents a distinctive case of bilateral congenital lacrimal fistulae in association with Down syndrome. It was managed successfully by primary fistulectomy and nasolacrimal duct probing.
PMCID: PMC3757640  PMID: 24014994
Down Syndrome; Fistulectomy; Lacrimal Fistula; Nasolacrimal Duct
13.  Congenital dacryocystocele: diagnosis and treatment 
Five children were diagnosed with congenital dacryocystocele; in all cases, the cystic lesion was unilateral; age ranged from 7 to 60 days (mean 29 days). The mean ultrasonography diameter of the cyst, at the time of the diagnosis, was 11.51 mm. Topical and systemic antibiotics and massage were prescribed. One patient had no recurrence of the dacryocystocele but 4 showed no improvement with medical treatment; they were submitted to successful probing in the first months of life under general anaesthesia. Nasal endoscopy revealed a nasolacrimal cyst in one patient. True dacryocystocele is relatively rare: ultrasound is a simple, non-invasive method that can reliably distinguish dacryocystocele from other pathological conditions. Several reports have described a variable natural course of these lesions but there are controversial opinions regarding their management. Initially, we treated this congenital anomaly with digital massage, and topical and systemic antibiotics. Probing under general anaesthesia was performed in the event of dacryocystitis or lack of resolution after a short trial period with digital massage. Particular attention was paid to nasal bilateral endoscopy to exclude a nasal obstruction caused by cystic swelling of the naso-lacrimal duct. When performed, the probing procedure was successful in all patients.
PMCID: PMC2689544  PMID: 19205594
Nasolacrimal duct; Dacryocystocele; Dacryocystitis; Nasolacrimal duct obstruction; Treatment
14.  Process of spontaneous resolution in the conservative management of congenital dacryocystocele 
To assess efficacy of the conservative management of patients with congenital dacryocystocele.
Materials and methods
This was a retrospective case series involving six sides of five infants with a dacryocystocele treated at Osaka Kaisei Hospital, Osaka, Japan. The conservative management protocol consisted of the application of warm compresses and massage over the mass, with the addition of antibiotics when dacryocystitis developed. Patient age at the time of resolution, presence of retrograde outflow of contents of dacryocystoceles from the puncta, and development of dacryocystitis were recorded.
The dacryocystocele was unilateral in four patients and bilateral in one patient. A nasal cyst was present in four patients without respiratory distress. The median patient age at the time of the diagnosis was 7 days (range 2–10 days). Conservative management was selected in all patients, and the dacryocystocele was resolved in all patients at a median patient age of 14.5 days (range 11–105 days). Two sides developed dacryocystitis, which resolved in a few days with antibiotic treatment. In those two sides, rupture of the dacryocystoceles to the common canaliculus with retrograde discharge of the contents from the puncta before the dacryocystitis developed was noted. For the other four treated sides, no such discharge or development of dacryocystitis was observed.
The findings of this study show that a dacryocystocele has a good chance of resolving spontaneously with conservative management and careful observation, and that rupture of the dacryocystocele to the common canaliculus might be an important precursor of dacryocystitis.
PMCID: PMC3942303  PMID: 24600200
dacryocystitis; congenital lacrimal obstruction; remnant; precursor; retrograde discharge
15.  Late Probing for Congenital Nasolacrimal Duct Obstruction 
To report the results of late nasolacrimal duct probing in patients with congenital nasolacrimal duct obstruction (NLDO).
This retrospective study was performed on a consecutive series of patients with congenital NLDO who underwent late (after 15 months of age) nasolacrimal duct probing for the first time.
Over a period of five years, 158 patients including 75 (47.4%) male and 83 (52.6%) female subjects with mean age of 3±4.2 years (range, 15 months to 37 years) underwent initial probing for NLDO. Nasolacrimal duct probing was performed unilaterally in 78% and bilaterally in 22% of the patients. Success rate was 75% overall, 72% in unilateral cases and 83% in bilateral instances. Success rate was not correlated with age at intervention.
Nasolacrimal duct probing seems to be reasonably successful for treatment of congenital NLDO in patients older than 15 months who are seen for the first time. Silicone intubation or dacryocystorhinostomy should be reserved for refractory cases.
PMCID: PMC3498545  PMID: 23198056
Lacrimal Duct Obstruction
16.  Dacryocystorhinostomy in patients lacking an ipsilateral nasal cavity 
Dacryocystorhinostomy (DCR) remains the surgery of choice for the treatment of epiphora secondary to nasolacrimal duct (NLD) obstruction. It involves creating a direct soft‐tissue anastomosis between the lacrimal sac and the ipsilateral nasal cavity, via an osteotomy created by removal of the floor of the lacrimal fossa and surrounding bone. Successful surgery clearly requires the presence of a nasal space and absence of this poses a surgical challenge.
We describe three patients with absent nasal cavity on the side of lacrimal obstruction, where DCR was performed by the creation of an anastomosis between the lacrimal sac and the contralateral nasal space.
PMCID: PMC1857647  PMID: 17035281
17.  Probing for Congenital Nasolacrimal Duct Obstruction in Older Children 
The purpose of this study was to evaluate the role of probing in congenital nasolacrimal duct obstruction in children age 2 years and older and to establish factors predictive of the outcome.
Materials and Methods:
A prospective study was conducted on consecutive patients older than 24 months with congenital nasolacrimal duct obstruction. All patients were treated with a simple nasolacrimal duct probing as primary treatment. Outcome measures included an ophthalmologic examination plus a parental history of residual symptoms at one and 6 months after surgery.
A total of 82 children with a mean age of 34.5 months (range, 24 months to 60 months) underwent nasolacrimal duct probing. The complete response rate was 54%. Partial response and failure were observed in 25% and 20.8% of the eyes, respectively. Bilateral obstruction was associated with failure of probing (P = 0.007, Odds Ratio: 5.76). However, age older than 36 months was not associated with the failure rate.
Primary probing maintains a high success rate without any age related decline in congenital nasolacrimal duct obstruction.
PMCID: PMC3841956  PMID: 24339688
Congenital Nasolacrimal Obstruction; Probing; Epiphora
18.  Balloon Catheter Dilation and Nasolacrimal Intubation for Treatment of Nasolacrimal Duct Obstruction Following a Failed Probing 
Archives of ophthalmology  2009;127(5):633-639.
To compare the outcome of balloon catheter dilation and nasolacrimal intubation as treatments for congenital nasolacrimal duct obstruction (NLDO) after a failed probing in children less than 4 years of age
We conducted a prospective, non-randomized multicenter study which enrolled 159 children aged 6 to <48 months who had a history of a single failed nasolacrimal duct probing and had at least one of the following clinical signs of NLDO present: epiphora, mucous discharge and/or increased tear lake. One hundred ninety-nine eyes underwent either balloon catheter nasolacrimal duct dilation or nasolacrimal duct intubation. Treatment success was defined as no epiphora, mucous discharge or increased tear lake present at the outcome visit six months after surgery.
Treatment success was reported in 65 of 84 eyes (77%, 95% CI = 65% to 85%) in the balloon group compared with 72 of 88 eyes (84%, 95% CI = 74% to 91%) eyes in the intubation group (risk ratio for success for intubation vs. balloon = 1.08, 95% CI = 0.95 to 1.22).
Balloon catheter dilation and nasolacrimal duct intubation each alleviate the clinical signs of persistent nasolacrimal duct obstruction in a similar proportion of patients.
PMCID: PMC2682211  PMID: 19433712
19.  Impacted Primary Tooth and Tooth Agenesis: A Case Report of Monozygotic Twins 
In the present report, a case of 19 year-old monozygotic twin brothers with similar tooth agenesis and impacted primary teeth is presented. Both twins (HDH, DHH) had agenesis of ten and eleven teeth (respectively), third molars excluded, consistent with oligodontia and both had four impacted primary teeth and the permanent successors of all these primary teeth were congenitally missing. The occurrence of similarly located tooth agenesis and primary impacted teeth in monozygotic twins may suggest the influence of genetic factors in their etiology. In addition, primary tooth impaction may be related to congenitally missing tooth.
PMCID: PMC2634786  PMID: 19212538
Monozygotic twins; Hypodontia; Oligodontia; Impaction
20.  High Prevalence of Proposed Müllerian Duct Remnant Cysts on the Spermatic Duct in Wild Eurasian Otters (Lutra lutra) from Sweden 
PLoS ONE  2013;8(12):e84660.
The spermatic ducts (vasa deferentia) of 235 otters (Lutra lutra) found dead between 1999 and 2012 in Sweden were examined for presence of paraductular cysts. Single or multiple elongated uni- or bilateral cysts parallel to the spermatic duct were noted in 72% of the examined males. The cysts were adjacent to, but did not communicate with the lumen of the spermatic duct, and were usually located within a few centimeters of the testis and epididymis. The cysts are proposed to be congenital Müllerian duct remnants. Other morphologic abnormalities in the reproductive organs were not noted within this study. Possible causes of the incomplete regression of the embryonic female gonadal duct are exposure to environmental contaminants such as elevated concentrations of estrogen-like compounds (endocrine disrupting chemicals), inbreeding, or a naturally occurring anatomic defect. No obvious geographical pattern was observed for otters with or without cysts. This is the first study and description of cysts on the spermatic duct in otters.
PMCID: PMC3871573  PMID: 24376831
21.  Disease concordance and sex similarity in twins 
Disease patterns in twins may show the presence of genetic or of environmental causes. Two arguments of inference have been used. Discordances between monozygotic twins have been taken to indicate the presence of environmental determinants; and high levels of concordance in monozygotic (MZ) pairs compared with dizygotic (DZ) pairs have been taken to indicate the presence of genetic causes. Neither argument is rigorous and, at this level, neither is quantitative.
An investigator cannot always establish the zygosity of individual twin pairs, and many have therefore used indirect arguments, based upon Weinberg's differential method.1 Thus, the number of MZ pairs in a randomly selected sample of twin pairs may be estimated by subtracting the number of unlike-sexed (U) from the number of like-sexed pairs (L). The proportion of MZ pairs is then (L - U)/(L + U), and of DZ pairs 2U/(L + U). Cannings2 showed that in twins which are randomly selected, and when the proportion of males is 0·5, these formulae are maximum-likelihood estimators; also that their validity is unaffected by differential prenatal viability of MZ and DZ twins.
However, in the context of investigating aetiologies we need to ask whether these relationships remain true in twins which are not selected randomly, but because a particular disease occurred in one or both of the pair. This distinction has not always been clearly made in the past. It turns out to be crucial.
Smith,3 for example, was led to an erroneous conclusion with respect to the aetiology of Down's disease. This he later recognised,4 and showed that the formulation of a correct method for estimating the proportions of the MZ and DZ twins depended upon the prior choice of a model of pathogenesis. It was necessary to decide in advance whether the disease-determining events occurred before or after the point of MZ cleavage. Distortions of the Weinberg rule also occur in sex-linked recessive transmission where the U:L ratio among DZ pairs is other than 1:1; it is this ratio upon which the validity of the Weinberg method chiefly depends. For the investigator examining diseases the causes of which are not known, the necessity to make assumptions about the aetiology of the disease before he even begins his analysis introduces a disturbing circularity. These considerations provide the background to this paper.
PMCID: PMC1052031  PMID: 6444983
22.  Twin reversed arterial perfusion (TRAP) sequence in association with VACTERL association: a case report 
Twin reversed arterial perfusion (TRAP) sequence is a rare complication of multiple pregnancy caused by defects in early embryogenesis. The pump twin supplies the acardiac recipient twin with blood, and although the pump twin is usually structurally normal, congenital anomalies have sometimes been reported. We report a unique case of twin reversed arterial perfusion sequence with a prenatal diagnosis of VACTERL association in the surviving pump twin.
Case presentation
A 24-year-old Caucasian woman presented at 11 weeks' gestation with a monochorionic, monoamniotic twin pregnancy. A reversed arterial flow was noted on a Doppler imaging study coming from the larger, apparently normal twin to the smaller, grossly abnormal twin, and a diagnosis of twin reversed arterial perfusion sequence was made. Cardiac activity was undetectable in the recipient twin by 16 weeks' gestation. Further detailed assessment at 18 weeks' gestation revealed multiple congenital anomalies of the surviving pump twin, in keeping with a diagnosis of VACTERL association. A live infant girl was delivered at 39 weeks by elective cesarean section. She underwent extensive surgery with subsequent normal development at the age of two years.
The co-existence of two rare and complex conditions in this unique case raises interesting questions about the role of early defects in embryogenesis and their subsequent effects on fetal development. This case also highlights the importance of prenatal diagnosis of major congenital anomalies to the plan treatment, reduce morbidity and aid the survival of affected children.
PMCID: PMC3022672  PMID: 21176185
23.  Congenital scoliosis in monozygotic twins: case report and review of possible factors contributing to its development 
Scoliosis  2008;3:17.
The exact etiology of congenital scoliosis remains unknown as yet. It seems that its development may be influenced by both genetic predisposition and environmental factors, at varying degrees. International bibliography features few cases of monozygotic twins with congenital scoliosis. The aim of this study is to report a case in monozygotic twins and review the literature relating to the description of similar cases as well as the pathophysiological mechanism involved in its development.
Clinical examination and simple X-rays revealed scoliosis of differing degrees and types in male monozygotic twins with moderate mental retardation and dyslalia.
Congenital scoliosis identified in both twins. In the first, this was manifested as left thoracic scoliosis, with Cobb angle of 34 degrees while in the second as left thoracolumbar scoliosis with Cobb angle of 10 degrees. Both were found to suffer from incarcerated hemivertebrae.
According to both its clinical identification and severity and to its course, not only the genetic but the environmental factors seem to play a leading role in the appearance of the condition.
PMCID: PMC2596087  PMID: 19017401
24.  Supernumerary, ectopic tooth in the maxillary antrum presenting with recurrent haemoptysis 
Head & Face Medicine  2010;6:26.
Ectopic eruption of teeth in non-dental sites is a rare phenomenon and can present in a variety of ways such as chronic or recurrent sinusitis, sepsis, nasolacrimal duct obstruction, headaches, ostiomeatal complex disease and facial numbness. However, presentation of such patients with recurrent haemoptysis has not been described in the literature so far. We have described a case of an ectopic, supernumerary molar tooth in the maxillary antrum in a patient who initially presented with haemoptysis.
Case presentation
A 45-year-old male presented with a 2-month history of episodic haemoptysis. A pedunculated growth from the inferior nasal turbinate was seen with fibre-optic visualization. Although the patient was empirically started on antibiotic and anti-allergic therapy, there was no improvement after a few weeks and the patient had recurrent episodes of haemoptysis. Fibre-optic visualization was repeated showing bilateral osteomeatal erythema. Computed tomography scan of the paranasal sinuses demonstrated complete opacification of the left maxillary antrum along with a focal area of density comparable to bone. An ectopic, supernumerary molar tooth was found in the left maxillary antrum on endoscopic examination and subsequently removed. In addition, copious purulent discharge was seen. Post-operatively, the patient was treated with a 10-day course of oral amoxicillin-clavulanate. On follow-up, he reported resolution of symptoms.
Recurrent haemoptysis has not been described as a presentation for a supernumerary, ectopic tooth in literature before. We recommend that in patients with sinusitis-type of opacification of maxillary antrum and whose condition is refractory to conventional medical treatment, consideration should be given to the investigation of possible underlying anomalies as the cause of such symptoms. Presence of foreign bodies and ectopic teeth in paranasal sinuses can be reliably excluded with the use of appropriate radiological imaging and endoscopic examination.
PMCID: PMC2992486  PMID: 21070657
25.  Thyroid Hypoplasia as a Cause of Congenital Hypothyroidism in Monozygotic Twins Concordant for Rubinstein-Taybi Syndrome. 
Rubinstein-Taybi syndrome (RSTS), a genetic disorder characterized by growth retardation, mental deficiency, dysmorphic face, broad thumbs and large toes, generally affects monozygotic twins concordantly. Thyroid hypoplasia (TH) is a common cause of congenital hypothyroidism (CH) and often accompanies dysmorphic syndromes. A pair of female twins were admitted to our neonatology unit 16 hours after delivery. They were born at 35 weeks of gestation. Both twins had an unusual dysmorphic facial appearance with microcephaly, as well as broad short thumbs and large toes. Based on the presence of characteristic dysmorphic features, the twins were diagnosed as RSTS. Thyroid function tests in the first twin revealed the following results: free thyroxine (T4) 8.4 pg/mL, thyrotropin (TSH) 4.62 mIU/L, thyroglobulin (TG) 213.24 ng/mL and a normal level of urinary iodine excretion (UIE). Thyroid function test results in the second twin in the second week were: free T4 5.9 pg/mL, TSH 9.02 mIU/L, TG 204.87 ng/mL, and normal UIE levels. Thyroid volumes were 0.36 mL and 0.31 mL in the first and second twin, respectively. TH was confirmed by technetium 99 m pertechnetate thyroid scans in both infants. Thyroid function tests normalized with L-thyroxine replacement therapy (10 μg/kg/day) around the end of the 3rd week of life. The infants were discharged planning their follow-up by both endocrinology and cardiology units. The rarity of cases of twins with RSTS (concordant) co-existing with CH led us to present this report.
Conflict of interest:None declared.
PMCID: PMC3065314  PMID: 21448332
Rubinstein-Taybi syndrome; monozygotic twins; congenital hyperthyroidism; thyroid hypoplasia

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