Fabry disease is an X-linked lysosomal storage disorder resulting in a multiple-system disorder with a wide spectrum of physical signs and symptoms, predominantly affecting the central and peripheral nervous systems, skin, heart, kidneys, and eyes.
We describe the case of a 26-year-old European Caucasian man who had Fabry disease and who presented with episodic sudden unilateral hearing loss and was treated with glucocorticoids, pentoxifylline, hyperbaric oxygen, and fluoride because of concomitant audiometric evidence of otosclerosis. This case demonstrates the partial and transient beneficial effect of standard treatment for sudden hearing loss not related to Fabry disease and analyzes the possible connection between typical Fabry disease inner-ear lesions and otosclerosis. Whereas hearing loss has been described in connection with Fabry disease, otosclerosis-associated hearing loss in Fabry disease has not yet been described.
Although progressive hearing loss in patients with Fabry disease seems to be influenced by replacement therapy, few data concerning treatment of sudden hearing loss are available. The lack of literature concerning the pathogenesis of the otological involvement in Fabry disease makes it impossible to identify a connection between the latter and otosclerosis. Therefore, this report may help to reinforce the importance of a thorough evaluation of hearing in patients with Fabry disease and may be of help with therapeutic decision-making.
Fabry disease (FD) is a progressive, X-linked inherited disorder of glycosphingolipid metabolism due to deficient or absent lysosomal α-galactosidase A activity. FD is pan-ethnic and the reported annual incidence of 1 in 100,000 may underestimate the true prevalence of the disease. Classically affected hemizygous males, with no residual α-galactosidase A activity may display all the characteristic neurological (pain), cutaneous (angiokeratoma), renal (proteinuria, kidney failure), cardiovascular (cardiomyopathy, arrhythmia), cochleo-vestibular and cerebrovascular (transient ischemic attacks, strokes) signs of the disease while heterozygous females have symptoms ranging from very mild to severe. Deficient activity of lysosomal α-galactosidase A results in progressive accumulation of globotriaosylceramide within lysosomes, believed to trigger a cascade of cellular events. Demonstration of marked α-galactosidase A deficiency is the definitive method for the diagnosis of hemizygous males. Enzyme analysis may occasionnally help to detect heterozygotes but is often inconclusive due to random X-chromosomal inactivation so that molecular testing (genotyping) of females is mandatory. In childhood, other possible causes of pain such as rheumatoid arthritis and 'growing pains' must be ruled out. In adulthood, multiple sclerosis is sometimes considered. Prenatal diagnosis, available by determination of enzyme activity or DNA testing in chorionic villi or cultured amniotic cells is, for ethical reasons, only considered in male fetuses. Pre-implantation diagnosis is possible. The existence of atypical variants and the availability of a specific therapy singularly complicate genetic counseling. A disease-specific therapeutic option - enzyme replacement therapy using recombinant human α-galactosidase A - has been recently introduced and its long term outcome is currently still being investigated. Conventional management consists of pain relief with analgesic drugs, nephroprotection (angiotensin converting enzyme inhibitors and angiotensin receptors blockers) and antiarrhythmic agents, whereas dialysis or renal transplantation are available for patients experiencing end-stage renal failure. With age, progressive damage to vital organ systems develops and at some point, organs may start to fail in functioning. End-stage renal disease and life-threatening cardiovascular or cerebrovascular complications limit life-expectancy of untreated males and females with reductions of 20 and 10 years, respectively, as compared to the general population. While there is increasing evidence that long-term enzyme therapy can halt disease progression, the importance of adjunctive therapies should be emphasized and the possibility of developing an oral therapy drives research forward into active site specific chaperones.
Fabry disease (FD, OMIM 301500) is an X-linked inborn error of glycosphingolipid metabolism due to the deficient activity of alpha-galactosidase A, a lysosomal enzyme. While the progressive systemic deposition of uncleaved glycosphingolipids throughout the body is known to have protean clinical manifestations, few data are available regarding the cochlear involvement.
We non-invasively investigated cochlear functions in 22 consecutive hemizygous males (age 19–64 years, mean 39) affected with classic FD. Conventional audiometry, tympanometry, ABR audiometry, otoacoustic emissions were performed in all patients, together with medical history record and physical examination as part of an exhaustive baseline evaluation prior to enzyme replacement therapy.
A total of 12 patients (54.5%) with classic FD were found to have abnormal audition. Five patients had progressive hearing loss and seven patients (32%) experienced sudden deafness. In addition, a hearing loss on high-tone frequencies was found in 7 out of the 10 remaining patients without clinical impairment, despite their young age at time of examination. The incidence of hearing loss appeared significantly increased in FD patients with kidney failure (P < 0.01) or cerebrovascular lesions (P < 0.01), whereas there was no correlation with left ventricular hypertrophy. In addition, tinnitus aurium was also found in six patients (27%).
This is the first evidence of a high incidence of both progressive hearing loss and sudden deafness in a cohort of male patients affected with classic Fabry disease. The exact pathophysiologic mechanism(s) of the cochlear involvement deserves further studies.
This study aimed to evaluate audiological and vestibular involvement in Fabry disease and the effects of enzyme replacement therapy with human α-galactosidase A. The study population comprised 20 patients (11 males, 9 females) aged 15-69 years (mean 39.7). Patients underwent a complete clinical and instrumental evaluation before starting and during enzyme replacement therapy. Median follow-up was 51.5 months (range 25-73). Nine patients (45%) complained of hearing symptoms (hearing loss, tinnitus); for six of them the onset and/or progression of the hearing loss were sudden. Vertigo or dizziness was reported by 6 patients (30%). Audiological evaluation showed a sensorineural hearing loss in 18 ears (45%; 10 in male patients, 8 in females). The hearing thresholds for 0.5, 1, 2 and 4 kHz frequencies ranged from 10 to 65 dB HL. Hearing loss was unilateral in 8 cases (40%; 4 in male patients, 4 in females). Also high frequency hearing loss for 4 and 8 kHz was evaluated. No signs of retro-cochlear lesions were observed by means of otoacoustic emissions and auditory brainstem response. Vestibular examinations showed a functional impairment in 7 ears (17.5%, all male patients). During enzyme replacement therapy the auditory function showed some degrees of worsening but no significant changes were observed at statistical analysis. In conclusion involvement of the inner ear is common in men and women with Fabry disease. In this study, a high incidence of cochlear hearing loss was found, which was typically unilateral and showed onset and/or progression by sudden episodes. Vascular or hydropic mechanisms could be hypothesized to explain audiological findings. Vestibular involvement showed a lower incidence and different pattern, thus suggesting that several patho-physiological mechanisms could play a role in determining inner ear damage in Fabry disease. Results obtained show that enzyme replacement therapy may stabilize hearing function; however, further studies on the physiopathology of the inner ear damage are needed.
Inner ear; Sensorineural hearing loss; Fabry disease; Vestibular damage; Enzyme replacement therapy; α-galactosidase A
Fabry disease is a lysosomal X-linked enzyme deficiency of α-galactosidase A associated with an increased mortality and morbidity due to renal failure, cardiac disease and early onset stroke.
We examined the functional blood flow response of the brain after visual stimulation (reversing checkerboard pattern), and cerebral vasoreactivity following acetazolamide (15 mg/kg) with [15O]H2O and positron emission tomography (PET) in Fabry disease. Twenty-six hemizygous patients (age range 19–47 years) were enrolled in a randomized double-blind placebo-controlled 6-month trial of enzyme replacement therapy administered by intravenous infusion every two weeks. Regional cerebral blood flow (rCBF) was measured with PET at the beginning and end of the trial.
Fabry patients had a significantly greater increase in rCBF following visual stimulation and acetazolamide challenge compared to controls. Visual reactivity was normal. The time for recovery of the cerebral vasculature following acetazolamide was prolonged in Fabry patients compared to controls. The abnormal rCBF response induced by visual stimulation and acetazolamide decreased significantly following enzyme replacement therapy, as did the prolonged recovery of the cerebral vasculature.
Enzyme replacement therapy reverses the exaggerated cerebrovascular response in Fabry disease.
Fabry disease, OMIM 301500, is a progressive multisystem storage disorder due to the deficiency of α-galactosidase A (GALA). Neurological and vascular manifestations of this disorder with regard to hearing loss have not been analysed quantitatively in large cohorts. We conducted a retrospective cross sectional analysis of hearing loss in 109 male and female patients with Fabry disease who were referred to and seen at the Clinical Center of the National Institutes of Health, Bethesda, MD, USA on natural history and enzyme replacement study protocols. There were 85 males aged 6–58 years (mean 31 years, SD 13) and 24 females aged 22–72 years (mean 42 years, SD 12). All patients underwent a comprehensive audiological evaluation. In addition, cerebral white matter lesions, peripheral neuropathy, and kidney function were quantitatively assessed. HL95, defined as a hearing threshold above the 95th percentile for age and gender matched normal controls, was present in 56% [95% CI (42.2–67.2)] of the males. Prevalence of HL95 was lower in the group of patients with residual GALA enzyme activity compared with those without detectable activity (33% versus 63%) HL95 was present in the low-, mid- and high-frequency ranges for all ages. Male patients with HL95 had a higher microvascular cerebral white matter lesion load [1.4, interquartile range (IQR) 0–30.1 ± versus 0, IQR 0–0], more pronounced cold perception deficit [19.4 ± 5.5 versus 13.5 ± 5.5 of just noticeable difference (JND) units] and lower kidney function [creatinine: 1.6 ± 1.2 versus 0.77 ± 0.2 mg/dl; blood urea nitrogen (BUN): 20.1 ± 14.1 versus 10.3 ± 3.28 mg/dl] than those without HL95 (P < 0.001). Of the females, 38% had HL95. There was no significant association with cold perception deficit, creatinine or BUN in the females. Word recognition and acoustic reflexes analyses suggested a predominant cochlear involvement. We conclude that hearing loss involving all frequency regions significantly contributes to morbidity in patients with Fabry disease. Our quantitative analysis suggests a correlation of neuropathic and vascular damage with hearing loss in the males. Residual GALA activity appears to have a protective effect against hearing loss.
Fabry disease; stroke; hearing impairment; peripheral neuropathy; X-linked disorder
Fabry disease (FD) is caused by progressive accumulation of neutral glycosphingolipids, including in ganglion neural and vascular endothelial cells, as a result of lysosomal α-galactosidase deficiency. High frequencies progressive sensorineural hearing loss (HL), sudden deafness, tinnitus and dizziness are otological symptoms frequently reported.
A 45-year-old man with FD, on haemodialysis since age 25, complaining of progressive HL, was started on enzyme replacement therapy (ERT) because of cardiac complications. A bilateral sloping sensorineural HL was found at baseline audiological evaluation. Computed tomography of the ears showed enlargement of the intradiploic vascular channels, principally in the petrous bone. The magnetic resonance angiography showed elongation and ectasia of the middle cerebral arteries and the arteries of the Circle of Willis, particularly the internal carotid and the basilar arteries. Follow-up audiological evaluations documented progressive worsening of HL, mainly in the high frequencies range, despite high dose ERT and evidence of cardiac improvement.
The intradiploic vascular abnormalities of the temporal bones reported herein have never been described in association with FD and may have contributed to the pathogenesis of progressive HL, by a ‘stealing’ effect upon the cochlear blood supply (like in cavernous haemangioma of the internal auditory meatus), in addition to the other mechanisms of ischaemic injury to the Organ of Corti described in FD. This clinical observation shows the value of comprehensive neuroimaging investigation of HL in FD and emphasizes the importance of early institution of specific therapy, before the occurrence of irreversible inner ear lesions and hearing damage.
Fabry patients have symptoms and signs compatible with autonomic dysfunction. These symptoms and signs are considered to be due to impairment of the peripheral nervous system, but findings indicative of autonomic neuropathy in other diseases, such as orthostatic intolerance and male sexual dysfunction, are infrequently reported in Fabry disease. The aim of our study was to investigate autonomic symptoms and cardiovascular autonomic function in a large cohort of male and female Fabry patients.
Forty-eight Fabry patients (15 male, 30 treated with enzyme replacement therapy) and 48 sex- and age-matched controls completed a questionnaire on autonomic symptoms (the Autonomic Symptom Profile). Thirty-six Fabry patients underwent cardiovascular function tests.
The Autonomic Symptom Profile revealed a significantly higher sum score in Fabry patients than in healthy control subjects (22 versus 12), but a relatively low score compared to patients with proven autonomic neuropathy. Fabry patients scored worse than healthy controls in the orthostatic intolerance domain. Scores in the male sexual dysfunction domain were comparable between healthy controls and male Fabry patients. The cardiovascular autonomic function tests revealed only mild abnormalities in seven patients. None of these seven patients showed more than one abnormal test result. Enzyme replacement therapy was not associated with less severe disease, lower ASP scores or less frequent abnormal cardiovascular function test results.
Male sexual function and autonomic control of the cardiovascular system are nearly normal in Fabry patients, which cast doubt on the general accepted assumption that autonomic neuropathy is the main cause of symptoms and signs compatible with autonomic dysfunction in Fabry disease. Possibly, end-organ damage plays a key role in the development of symptoms and signs in Fabry patients. An exceptional kind of autonomic neuropathy is another but less likely explanation.
Twin boys with Fabry's disease and 6 affected relatives were described. Limb pains and retinal vessel tortuosity were present but no patient had angiokeratomata. One boy had a severe enteropathy with small and large bowel involvement which was investigated. Thin-layer chromatography showed that excesses of ceramide di- and trihexosides were excreted in the urine. Leucocyte α-galactosidase activity was measured: hemizygous males showed very low activity, while obligate and probable heterozygous females had values intermediate between those of the patients and the normal controls.
We present here a large Israeli-Arab kindred with hereditary deafness. In this family 55 deaf subjects (29M, 26F), who are otherwise healthy, have been identified and traced back five generations to one common female ancestor. The deafness is progressive in nature, usually presenting in infancy and childhood. Audiometry on six deaf and seven unaffected subjects was consistent with severe to profound sensorineural hearing loss. Based on formal family segregation analysis, the inheritance of deafness in this family closely fits the expectation of a two locus model owing to the simultaneous mutation of a mitochondrial gene and an autosomal recessive gene. Thus, this disorder appears to have the unusual features of being an inherited tissue specific mitochondrial disease and apparently requiring the homozygous presence of a nuclear gene for clinical expression. Most importantly, this disorder presents a unique opportunity to investigate the molecular basis of hereditary non-syndromic deafness and normal hearing.
Kidney involvement with progressive loss of kidney function (Fabry nephropathy) is an important complication of Fabry disease, an X-linked lysosomal storage disorder arising from deficiency of α-galactosidase activity. Clinical trials have shown that enzyme replacement therapy (ERT) with recombinant human α-galactosidase clears globotriaosylceramide from kidney cells, and can stabilize kidney function in patients with mild to moderate Fabry nephropathy. Recent trials show that patients with more advanced Fabry nephropathy and overt proteinuria do not respond as well to ERT alone, but can benefit from anti-proteinuric therapy given in conjunction with ERT. This review focuses on the use of enzyme replacement therapy with agalsidase-alfa and agalsidase-beta in adults with Fabry nephropathy. The current results are reviewed and evaluated. The issues of dosing of enzyme replacement therapy, the use of adjunctive agents to control urinary protein excretion, and the individual factors that affect disease severity are reviewed.
agalsidase; enzyme replacement therapy; Fabry nephropathy; anti-proteinuric therapy
Sarcoidosis is an inflammatory multisystem disorder of unknown cause. Approximately 5-7% of patients manifest symptoms of central nervous system involvement, or neurosarcoidosis. Cranial neuropathy usually entails facial nerve palsy and optic neuritis. Sudden hearing loss has been reported in fewer than 20 cases. Herewith, two new cases of sudden hearing loss due to probable neurosarcoidosis are reported, each having a quite different clinical course. In one case, unilateral sudden hearing loss and facial palsy were the presenting symptoms of systemic sarcoidosis, while in the second, unilateral sudden deafness occurred despite ongoing immunosuppressive treatment for systemic sarcoidosis.
Sudden hearing loss; Sarcoidosis; Neurosarcoidosis; Auditory brainstem response; Magnetic resonance imaging
The increasing incidence of central nervous system (CNS) lymphoma in the general population, especially in young adults with AIDS, should alert the otolaryngologist that in future there will be an even greater incidence of this rare disease. It may be responsible for hearing loss accompanied by other neurological deficits. CNS lymphoma often has a rapidly progressive course. Early diagnosis and rapid therapy are crucial for a better prognosis. We report a case of primary CNS lymphoma involving both internal auditory canals that presented with sudden deafness and disequilibrium accompanied by facial and abducens nerve palsy.
Lymphoma; hearing loss; internal auditory canal
The X-chromosomal-linked lysosomal storage disorder Fabry disease can lead to life-threatening manifestations. The pathological significance of the Fabry mutation D313Y is doubted, because, in general, D313Y patients do not present clinical manifestations conformable with Fabry disease. This is in contrast to the analysis of the alpha-galactosidase A activity, which is reduced in D313Y patients. We report a comprehensive clinical, biochemical and molecular genetic analysis of two patients with a D313Y mutation. The alpha-galactosidase A activity was reduced in both patients. No Fabry symptoms or Fabry organ involvement was detected in these patients. The new biomarker lyso-Gb3, severely increased in classical Fabry patients, was determined and in both patients lyso-Gb3 was below the average of a normal population.
Our data for the first time not only clinically but also biochemically supports the hypothesis that the D313Y mutation is not a classical one, but a rare variant mutation.
During the last year patients presenting with progressive bilateral or sudden sensorineural deafness of unknown aetiology have been investigated for possible abnormal immune activity. Twenty-six cases are reported in which significantly raised circulating immune complexes were present, together with 2 cases of clinical autoimmune deafness where the complexes were normal. Thirty-six control subjects were also studied. Following a review of the clinical features, the pathogenesis of this new association with sensorineural deafness is discussed. In some cases the aetiology is probably autoimmune, and in others related to infection. In certain patients the deafness has been partly reversed by medical treatment with systemic steroids or plasma exchange. It is hypothesized that circulating immune complexes may reflect a previously unrecognized final common pathophysiological pathway in a variety of cochleovestibular disorders.
Fabry disease is an X-linked recessive and progressive disease caused by α-galactosidase A (α-GaL A) deficiency. We sought to assess the prevalence of unrecognized Fabry disease in dialysis-dependent patients and the efficacy of serum globotriaosylceramide (GL3) screening.
A total of 480 patients of 1,230 patients among 17 clinics were enrolled. Serum GL3 levels were measured by tandem mass spectrometry. Additionally, we studied the association between increased GL3 levels and cardiovascular disease, cerebrovascular disease, or left ventricular hypertrophy.
Twenty-nine patients had elevated serum GL3 levels. The α-GaL A activity was determined for the 26 patients with high GL3 levels. The mean α-GaL A activity was 64.6 nmol/hr/mg (reference range, 45 to 85), and no patient was identified with decreased α-GaL A activity. Among the group with high GL3 levels, 15 women had a α-GaL A genetics analysis. No point mutations were discovered among the women with high GL3 levels. No correlation was observed between serum GL3 levels and α-GaL A activity; the Pearson correlation coefficient was 0.01352 (p = 0.9478). No significant correlation was observed between increased GL3 levels and the frequency of cardiovascular disease or cerebrovascular disease.
Fabry disease is very rare disease in patients with end-stage renal disease. Serum GL3 measurements as a screening method for Fabry disease showed a high false-positive rate. Thus, serum GL3 levels determined by tandem mass spectrometry may not be useful as a screening method for Fabry disease in patients with end stage renal disease.
Fabry disease; Globotriaosylceramide; End-stage renal disease
Fabry disease, an X-linked recessive disorder of glycosphingolipid catabolism, results from the deficient activity of the lysosomal hydrolase, alpha-galactosidase. Southern hybridization analysis of the alpha-galactosidase gene in affected hemizygous males from 130 unrelated families with Fabry disease revealed six with different gene rearrangements and one with an exonic point mutation resulting in the obliteration of an Msp I restriction site. Five partial gene deletions were detected ranging in size from 0.4 to greater than 5.5 kb. Four of these deletions had breakpoints in intron 2, a region in the gene containing multiple Alu repeat sequences. A sixth genomic rearrangement was identified in which a region of about 8 kb, containing exons 2 through 6, was duplicated by a homologous, but unequal crossover event. The Msp I site obliteration, which mapped to exon 7, was detected in an affected hemizygote who had residual enzyme activity. Genomic amplification by the polymerase chain reaction and sequencing revealed that the obliteration resulted from a C to T transition at nucleotide 1066 in the coding sequence. This point mutation, the first identified in Fabry disease, resulted in an arginine356 to tryptophan356 substitution which altered the enzyme's kinetic and stability properties. The detection of these abnormalities provided for the precise identification of Fabry heterozygotes, thereby permitting molecular pedigree analysis in these families which revealed paternity exclusions and the first documented new mutations in this disease.
About 120 million people worldwide suffer from congenital (early-onset) hearing loss. Thirty percent of them have syndromic hearing loss and the remaining 70% have non-syndromic hearing loss. In addition, a large number of elderly people worldwide suffer from age-related (late-onset) hearing loss. c-Ret and c-RET have been shown to be essential for the development and maintenance of neurons including the enteric nervous system (ENS) in mice and humans. Impairments of endothelin receptor B (EDNRB) and SOX10 have been shown to cause a significantly increased risk of dominant sensorineural deafness in Hirschsprung disease (HSCR) patients. We have recently shown that impairments of tyrosine 1062 (Y1062) phosphorylation in c-Ret causes syndromic congenital deafness in mice and humans and non-syndromic age-related hearing loss with neurodegeneration of spiral ganglion neurons (SGNs) in mice. This review focuses on the pathogenesis of hearing loss caused by impairments of c-Ret.
c-Ret; congenital deafness; age-related deafness; tyrosine kinase; spiral ganglion neuron; neurodegeneration
Lysosomal storage disorders are a group of disorders characterised by the deficiency of a specific lysosomal hydrolase. These diseases are rare, with only a few hundred patients in the Netherlands. Fabry's disease, an X-linked lysosomal storage disorder, is caused by a deficiency of the lysosomal enzyme α-galactosidase A which results in, among other things, left ventricular hypertrophy, renal failure and cerebrovascular events. Patients with Fabry's disease, especially males, have a decreased life expectancy. Recent studies have shown that Fabry's disease may be much more common among patients with left ventricular hypertrophy (LVH) than previously thought. Up to 7% of male patients with left ventricular hypertrophy and up to 12% of female patients with unexplained LVH were found to suffer from Fabry's disease. Thus, Fabry's disease should be considered in patients with unexplained LVH. This case report summarises the main features of the disease. In addition recent developments concerning prevalence, diagnosis and the current available treatments are discussed and an algorithm on who and how to screen for Fabry's disease is presented.
lysosomal storage disorders; left ventricular hypertrophy; diagnosis; treatment; Fabry's disease
Background. In Fabry nephropathy, alpha-galactosidase deficiency leads to accumulation of glycosphingolipids in all kidney cell types, proteinuria and progressive loss of kidney function.
Methods. An international working group of nephrologists from 11 Fabry centres identified adult Fabry patients, and pathologists scored histologic changes on renal biopsies. A standardized scoring system was developed with a modified Delphi technique assessing 59 Fabry nephropathy cases. Each case was scored independently of clinical information by at least three pathologists with an average final score reported.
Results. We assessed 35 males (mean age 36.4 years) and 24 females (43.9 years) who mostly had clinically mild Fabry nephropathy. The average serum creatinine was 1.3 mg/dl (114.9 μmol/l); estimated glomerular filtration rate was 81.7 ml/min/1.73 m2 and urine protein to creatinine ratio was 1.08 g/g (122.0 mg/mmol). Males had greater podocyte vacuolization on light microscopy (mean score) and glycosphingolipid inclusions on semi-thin sections than females. Males also had significantly more proximal tubule, peritubular capillary and vascular intimal inclusions. Arteriolar hyalinosis was similar, but females had significantly more arterial hyalinosis. Chronic kidney disease stage correlated with arterial and glomerular sclerosis scores. Significant changes, including segmental and global sclerosis, and interstitial fibrosis were seen even in patients with stage 1–2 chronic kidney disease with minimal proteinuria.
Conclusions. The development of a standardized scoring system of both disease-specific lesions, i.e. lipid deposition related, and general lesions of progression, i.e. fibrosis and sclerosis, showed a spectrum of histologic appearances even in early clinical stage of Fabry nephropathy. These findings support the role of kidney biopsy in the baseline evaluation of Fabry nephropathy, even with mild clinical disease. The scoring system will be useful for longitudinal assessment of prognosis and responses to therapy for Fabry nephropathy.
chronic kidney disease; Fabry disease; pathology; sclerosis; scoring
We describe two female monozygotic (MZ) twins heterozygous for Fabry disease, an X linked disorder resulting from the deficient activity of alpha-galactosidase A. While one of the twins was clinically affected, the other was asymptomatic. Enzymatic assay of alpha-galactosidase in blood leucocytes, skin fibroblasts, Epstein-Barr virus transformed lymphoid cell lines, and hair follicles of the twins and their parents confirmed the heterozygous status of the twins and indicated that Fabry disease had occurred as a result of a de novo mutation. The son of the unaffected twin sister was shown to be hemizygous. Molecular analysis of the alpha-galactosidase A gene permitted the identification of an as yet undescribed point mutation at position 10182 of exon 5 which causes an Asp to Asn substitution at codon 231. Single strand conformation polymorphism (SSCP) analysis again showed the heterozygous status of the twins and a normal pattern in their parents. The basis for the discordant expression of this d novo mutation in the twins was investigated by studying their X inactivation status. Analysis of the inactive X specific methylation at the androgen receptor gene showed unbalanced inactivation in the twins' fibroblasts and in opposite directions. While the maternally derived X chromosome was preferentially active in the asymptomatic twin, the paternal X chromosome was active in the other, affected twin and was found in her hemizygotic nephew. These data suggest that the paternal X chromosome carries the de novo alpha-galactosidase A mutation and that uneven X inactivation is the underlying mechanism for disease expression in this novel female MZ twin pair. This is the first documented case of female twins discordant for Fabry disease.
Fabry disease, an X-linked lysosomal storage disorder, results from deficient activity of the enzyme α-galactosidase A. Affected males with the classic phoenotype have acroparaesthesias, hypohidrosis, and corneal opacities in childhood and develop renal failure, cardiac hypertrophy or strokes in the third to fifth decade of life. Some female heterozygotes are asymptomatic, some as severely affected as males. The natural history of Fabry patients includes transitory cerebral ischaemia and strokes, even in very young persons of both genders. The mechanism is partly due to vascular endothelial accumulation of GL-3. White matter lesions on MRI occur. Both males and females can be safely treated with enzyme replacement; and thus screening for Fabry disease of young stroke populations should be considered. There are, however, no hard data of treatment effect on mortality and morbidity. The analyses of results from ongoing studirs will add to the decision on whether or not to screen young stroke patients for Fabry disease. Finally, stroke prophylactic therapy should be used liberally in patients of both genders with verified Fabry disease. This includes primary prevention such as lifestyle counseling, targeting blood pressure, managing atrial fibrillation, diabetes mellitus, hyperlipidaemia, and ASA.
Non-syndromic hearing impairment is one of the most heterogeneous hereditary conditions, with more than 40 reported gene localisations. We have identified a large Dutch family with autosomal dominant non-syndromic sensorineural hearing impairment. In most patients, the onset of hearing impairment is in the first or second decade of life, with a slow decline in the following decades, which stops short of profound deafness. The hearing loss is bilateral, symmetrical, and only affects low and mid frequencies up to 2000 Hz. In view of the phenotypic similarities of this family with an American family that has been linked to chromosome 4p16.3 (DFNA6), we investigated linkage to the DFNA6 region. Lod score calculations confirmed linkage to this region with two point lod scores above 6. However, as haplotype analysis indicated that the genetic defect in this family is located in a 5.6 cM candidate region that does not overlap the DFNA6 region, the new locus has been named DFNA14.
Keywords: non-syndromic hearing impairment; genetic linkage analysis; DFNA6; DFNA14
The treatment of choice for sudden sensorineural hearing loss is still lacking. Many drugs have been used over the years, with varying results and steroids have proven to be effective in clinical trials, albeit systemic administration is associated with untoward side-effects and cannot be used in all patients. The transtympanic approach presents two main advantages: first, it allows higher concentrations in the inner ear environment and, second, it minimizes systemic absorption. Aim of the present investigation was to establish the effectiveness of transtympanic steroid treatment for sudden sensorineural hearing loss in patients in whom conventional treatment had failed. For this purpose, a prospective, non-randomized study was designed to evaluate hearing improvement in sudden sensorineural hearing loss patients treated with transtympanic steroids. A solution of methyl-prednisolone and sodium bicarbonate was administered, via a transtympanic injection, in 10 patients. Hearing levels were evaluated before treatment and on days 1, 7 and 30, thereafter. Improvement in hearing was observed in 70% of patients, moreover, in patients not usually considered amenable to this kind of treatment. Transtympanic steroid treatment is an effective and safe option for patients with sudden sensorineural hearing loss when conventional treatment regimens have failed. Further studies are needed to define the optimal dosage, route of administration and type of steroids.
Sensorineural hearing loss; Sudden hearing loss; Transtympanic therapy; Steroids
Fabry disease is an inherited metabolic disorder characterized by progressive lysosomal accumulation of lipids in a variety of cell types, including neural cells. Small, unmyelinated nerve fibers are particularly affected and small fiber peripheral neuropathy often clinically manifests at young age. Peripheral pain can be chronic and/or occur as provoked attacks of excruciating pain. Manifestations of dysfunction of small autonomic fibers may include, among others, impaired sweating, gastrointestinal dysmotility, and abnormal pain perception. Patients with Fabry disease often remain undiagnosed until severe complications involving the kidney, heart, peripheral nerves and/or brain have arisen.
An international expert panel convened with the goal to provide guidance to clinicians who may encounter unrecognized patients with Fabry disease on how to diagnose these patients early using simple diagnostic tests. A further aim was to offer recommendations to control neuropathic pain.
We describe the neuropathy in Fabry disease, focusing on peripheral small fiber dysfunction - the hallmark of early neurologic involvement in this disorder. The clinical course of peripheral pain is summarized, and the importance of medical history-taking, including family history, is highlighted. A thorough physical examination (e.g., angiokeratoma, corneal opacities) and simple non-invasive sensory perception tests could provide clues to the diagnosis of Fabry disease. Reported early clinical benefits of enzyme replacement therapy include reduction of neuropathic pain, and adequate management of residual pain to a tolerable and functional level can substantially improve the quality of life for patients.
Our recommendations can assist in diagnosing Fabry small fiber neuropathy early, and offer clinicians guidance in controlling peripheral pain. This is particularly important since management of pain in young patients with Fabry disease appears to be inadequate.
Diagnosis; Fabry Disease; Neuropathy; Pain; Treatment