Covered self expandable metallic airway stents (SEMS) have been used for benign tracheal stenosis, post intubation tracheal stenosis, tracheal burn or trauma, tracheo-broncho-malacia, and extrinsic compression of trachea. Their placement is considered to be permanent, with open surgery the only way to remove the stent, though there are few cases reports of their removal with the bronchoscope, but the complications after their removal are very high. In our patient, one and a half years after placement of SEMS, she developed cough with dyspnoea, video bronchoscopy showed stenosis above the level of stent with granulation tissue inside the stent, stent fracture in lower part and stent migration to right main bronchus, thus she had all conceivable complications of stent placement. The stent was removed with the help of rigid bronchoscope under general anaesthesia. She was discharged the following day. The case is being reported because it was unique in having all the possible complications of stent placement, and rare as we could take out the stent in Toto. Thirdly, the stent could be removed without any complication.
Granulation tissue inside the stent; stenosis above the stent; stent fracture; stent migration
The incidence of tracheo-esophageal (TO) fistula is on the rise, especially after palliative management for esophageal malignancies. We report a case of cancer of esophagus who after chemotherapy and radiotherapy developed TO fistula. Placement of an esophageal stent helped him in taking food orally, but his cough and dyspnoea continued to worsen. Fibreoptic bronchoscopy demonstrated a severely compressed trachea secondary to protrusion of esophageal stent which responded very well to an Ultraflex-covered tracheal stent and the patient achieved relief from cough and dyspnoea.
Fibreoptic bronchoscopy; tracheo-esophageal fistula; Ultraflex stent
Hemoptysis is defined as the spitting of blood derived from the lungs or bronchial tubes as a result of pulmonary or bronchial hemorrhage. There is a large chunk of patients with hemoptysis who do not respond to conservative treatment including use of cough suppressants, antibiotics, vitamin C, hemostatics, and anxiolytics. The advanced management of such a situation is bronchial artery embolization (BAE) or open thoracic surgery, which is often not possible. We have attempted a cheap, effective, and safe alternative in the form of intrabronchial instillation of glue (n-butyl cyanoacrylate) under vision with the help of a therapeutic video bronchoscope (OLYMPUS T-180). The glue is instilled through a polyethylene catheter placed through the working channel of the video bronchoscope.
Hemoptysis; video bronchoscopy; glue therapy; n-butyl cyanoacrylate (glue)
Genitourinary histoplasmosis is very rare and to our knowledge only four cases of epididymal histoplasmosis and nine cases of prostatic histoplasmosis have been reported in literature. We hereby report a case of a middle-aged male, who presented three years after renal transplant, with complaints of fever, pain, and swelling in the scrotum. Imaging disclosed an enlarged right epididymis with prostatic and retrotrigonal abscess, suggesting tuberculosis infection. However, histopathology of the epididymal biopsy revealed histoplasmosis, and the drained pus on culture confirmed infection with Histoplasma capsulatum.
Epididymis; histoplasmosis; prostate
Bronchopleural fistula (BPF) is a communication between the pleural space and bronchial tree.
Materials and Methods:
A series of 9 cases are reported where BPF was identified and managed with intrabronchial instillation of glue (N-butyl-cyanoacrylate) through a video bronchoscope.
Out of 9 patients the BPF was successfully sealed in 8 cases (88.88%). In 1 patient of postpneumonectomy, the fistula was big, that is >8 mm who had a recurrence after the procedure. In one case of pyopneumothorax the leak reduced slowly and it took us 14 days to remove the intercostal drainage tube. Rest of the patients had a favorable outcome. No complications were observed in a follow-up of 6 months.
In our opinion, it is a cost-effective, viable, and safe alternative compared with costly, time-consuming, and high-risk surgical procedures.
Bronchopleural fistula; intercostal drainage tube; N-butyl cyanoacrylate glue; video bronchoscopy
Hemoptysis is a very common symptom in the practice of pulmonary physicians of India. We present a case of uncontrolled hemoptysis managed with bronchial artery embolization. Bronchial artery embolization is an effective treatment for patients with hemoptysis. Serious complications are rare, but may occur if the arterial supply to other structures is compromised.
Bronchial artery embolization; bronchogenic carcinoma; fiber optic bronchoscopy; hemoptysis
HIV-associated nephropathy (HIVAN) is the manifestation of HIV genes expression by kidney cells in the presence of specific host factors. Recently, rapamycin (sirolimus) has been demonstrated to modulate the progression of HIVAN. We hypothesized that rapamycin would modulate the progression of HIVAN by attenuating HIV genes expression. To test our hypothesis, three weeks old Tg26 mice (n=6) were administered either vehicle or rapamycin (5 mg/kg/day, intraperitoneally) for eight weeks. At the end of experimental period, kidneys were harvested. In in vitro studies, human podocytes were transduced with either HIV-1 (NL4-3) or empty vector (EV), followed by treatment with either vehicle or rapamycin. Total RNA and proteins were extracted from renal tissues/ cellular lysates and HIV gene transcription/translation was measured by real time PCR and Western blotting studies. Renal histological slides were graded for glomerular sclerosis and tubular dilatation with microcyst formation. Rapamycin attenuated both glomerular and tubular lesions in Tg26 mice. Rapamycin decreased transcription of HIV genes both in renal tissues as well as in HIV-1 transduced podocytes. Our data strongly indicate that HIV-1 long terminal repeat-mediated transcriptional activity was targeted by rapamycin. Rapamycin enhanced podocyte NF-kB and CREB activities but then it decreased AP-1 binding activity. Since expression of HIV genes by kidney cells has been demonstrated to be the key factor in the development HIVAN, it appears that rapamycin-induced altered transcription of HIV genes might have partly contributed to its disease modulating effects.
Background: Pulmonary aspergillosis is commonly seen in immunocompromised individuals. A significant rise has been seen in these cases in the past decade, owing to growing number of patients with impaired immune status.
Aim: This study includes the detailed clinical and microbiological profiles of all the culture positive cases of pulmonary aspergillosis, detected in three years, from Jan 2008–Dec 2010, at our tertiary care centre.
Methods: A hospital based observational and retrospective study was conducted to study the clinico-microbiological characteristics of patients with pulmonary aspergillosis. Respiratory specimens which showed repeated isolation of Aspergillus were included in the study. Demographic details, clinical findings and predisposing factors were noted down for all the patients. Treatment of patients with antifungal agents and their responses to treatment were also documented.
Results: There were 22 patients with male to female ratio of 1.2:1 and mean age of 52.5 years. The most common underlying lung disease was presence of bronchial asthma in 27.3% (6/22) cases. Many patients (40.9%; 9/22) were on steroid treatment. Cough with expectoration was the most common symptom observed in 72.7% (16/22) cases. Microbiologically, microscopy showed positivity for the presence of gram positive, acutely branched, fungal hyphae, suggestive of Aspergillus, in all the cases. Aspergillus fumigatus was the predominant species that was isolated in 40.9% (9/22) cases. All the diagnosed patients were given either oral itraconazole or intravenous amphotericin B. A clinical improvement was observed in 72.5% (16/22) cases, but 27.3% (6/22) patients died.
Conclusion: Pulmonary aspergillosis presents with non-specific clinical and radiological findings. An early suspicion and diagnosis is essential, especially in patients with underlying lung disease, to prevent dissemination and invasion.
Aspergillus; Pulmonary aspergillosis,; Chronic obstructive pulmonary disease
Mycobacterium tuberculosis (Mtb) survives under oxidatively hostile environments encountered inside host phagocytes. To protect itself from oxidative stress, Mtb produces millimolar concentrations of mycothiol (MSH), which functions as a major cytoplasmic redox buffer. Here, we introduce a novel system for real-time imaging of mycothiol redox potential (EMSH) within Mtb cells during infection. We demonstrate that coupling of Mtb MSH-dependent oxidoreductase (mycoredoxin-1; Mrx1) to redox-sensitive GFP (roGFP2; Mrx1-roGFP2) allowed measurement of dynamic changes in intramycobacterial EMSH with unprecedented sensitivity and specificity. Using Mrx1-roGFP2, we report the first quantitative measurements of EMSH in diverse mycobacterial species, genetic mutants, and drug-resistant patient isolates. These cellular studies reveal, for the first time, that the environment inside macrophages and sub-vacuolar compartments induces heterogeneity in EMSH of the Mtb population. Further application of this new biosensor demonstrates that treatment of Mtb infected macrophage with anti-tuberculosis (TB) drugs induces oxidative shift in EMSH, suggesting that the intramacrophage milieu and antibiotics cooperatively disrupt the MSH homeostasis to exert efficient Mtb killing. Lastly, we analyze the membrane integrity of Mtb cells with varied EMSH during infection and show that subpopulation with higher EMSH are susceptible to clinically relevant antibiotics, whereas lower EMSH promotes antibiotic tolerance. Together, these data suggest the importance of MSH redox signaling in modulating mycobacterial survival following treatment with anti-TB drugs. We anticipate that Mrx1-roGFP2 will be a major contributor to our understanding of redox biology of Mtb and will lead to novel strategies to target redox metabolism for controlling Mtb persistence.
Approximately 30% of the global population is infected with Mycobacterium tuberculosis (Mtb). Persistence of Mtb in host phagocytes depends on its ability to resist oxidant-mediated antibacterial responses. Mycothiol (MSH) is the main antioxidant that provides an abundant source of reducing equivalent, which protects Mtb from oxidative stress encountered during infection. The majority of research into redox signaling in Mtb has relied on chemical analysis of MSH in whole cell extract, which creates oxidation artifacts and prohibits dynamic imaging of MSH redox state during infection. We have successfully developed a novel and noninvasive tool based on genetically encoded redox sensitive fluorescent probes to perform real-time measurement of mycothiol redox potential (EMSH) in Mtb during infection. For the first time we reveal the EMSH of virulent and avirulent mycobacterial strains, including drug-resistant clinical isolates. We used this technology and came to the surprising conclusion that within a single infected macrophage there is heterogeneity in the redox signature of individual Mtb bacilli. Importantly, we show that anti-TB drugs accelerate oxidative stress in Mtb within infected macrophages and redox heterogeneity can contribute to emergence of drug tolerant population. These findings have implications for mycobacterial persistence following treatment with anti-TB drugs.
Metabolism and immunity are inextricably linked both to each other and to organism-wide function, allowing mammals to adapt to changes in their internal and external environments. In the modern context of obesogenic diets and lifestyles, however, these adaptive responses can have deleterious consequences. In this review, we discuss the pleiotropic actions of inflammation and insulin resistance in metabolic homeostasis and disease. An appreciation of the adaptive context in which these responses arose is useful for understanding their pathogenic actions in disease.
Fibromatoses are a heterogeneous group of distinct entities which differ in biological behaviour, but arehistologically very similar. This group of fibrous tumor or tumor like lesions, present considerable difficulties in pathologic diagnosis. Aggressive fibromatosis (AF) of the oral or para-oral structures is a very uncommon finding and its intra-osseous component is even relatively unusual. Such lesions with their origin from within the bone are termed desmoplastic fibromatosis (DF). These lesions must be distinguished from other fibroblastic tumors of the head and neck such as benign fibrous histiocytoma (BFH), fibrosarcoma, nerve sheath tumors and tumors of muscular origin. The major challenge in dealing with lesions of fibromatosis is to avoid an overdiagnosis of fibrosarcoma or an underdiagnosis of reactive fibrosis.Problems of differential diagnosis concern a wide range of diseases and immunohistochemical analysis may be helpful in diagnosis. With respect to the patient’s post-operative well-being and if periodic follow-ups are guaranteed, the tumor should be carefully resected with only narrow safety margins. A rare case of aggressive desmoplastic fibromatosis in a 12–year–old girl is presented in this article with emphasis on the need and challenges for diagnosing such lesions as they have to be differentiated from other soft tissue tumors which display borderline pathological features regarding benign or malignant behaviour. Synonyms listed for the same include extra-abdominal desmoids, extra-abdominal fibromatosis, desmoids tumor, aggressive fibromatosis, juvenile desmoids-type fibromatosis, infantile fibromatosis.
Aggressive; Desmoplastic; Fibromatosis
A preterm neonate was noted to have diffuse blanching erythema around the mouth followed by appearance of bullous lesions on the upper back, lower neck and right scapular areas at 23 h of life. The bullae subsequently ruptured leaving an extremely tender, erythematous, denuded area of the skin, which extended over next few hours to involve most of the upper back and right shoulder regions. Nikolsky sign was positive. Clinical diagnosis of staphylococcal scalded skin syndrome was made. The throat, blood, urine and cerebrospinal fluid cultures did not yield any growth, but wound culture was positive for Staphylococcus aureus. Treatment included administration of intravenous fluids and vancomycin for 10 days. The wound area was covered with vaseline and sterile gauge dressings. On day 5 of life, epithelialisation began and was complete on the seventh day of life. She was discharged home with intact skin, without scars, on day 12 of life.
Detection of acute kidney injury is undergoing a dynamic revolution of biomarker technology allowing greater, earlier, and more accurate determination of diagnosis, prognosis, and with powerful implication for management. Biomarkers can be broadly considered as any measurable biologic entity or process that allows differentiation between normal function and injury or disease. The ADQI (Acute Dialysis Quality Initiative) had its Ninth Consensus Conference dedicated to synthesis and formulation of the existing literature on biomarkers for the detection of acute kidney injury in a variety of settings. In the papers that accompany this summary, ADQI workgroups fully develop key concepts from a summary of the literature in the domains of early diagnosis, differential diagnosis, prognosis and management, and concurrent physiologic and imaging measures.
Neurolymphomatosis (NL) refers to a lymphomatous infiltration of peripheral nerves associated with central nervous system or systemic lymphoma, or alternatively, neurodiagnostic evidence of nerve enhancement and/or enlargement beyond the dural sleeve in the setting of primary central nervous system lymphoma or systemic lymphoma. NL is a rare complication of systemic cancer with heterogeneous clinical presentations and an elusive diagnosis. Diagnosis usually requires the demonstration of infiltrating malignant lymphocytes in the peripheral nerve. Infiltration of brain parenchyma, meninges or Virchow–Robin spaces is characteristic of systemic disease at autopsy. We describe a patient presenting with biopsy negative NL affecting exclusively the peripheral nervous system at autopsy.
neurolymphomatosis; non-Hodgkin lymphoma; peripheral neuropathy
To compare the efficacy and surgical outcome of treatment of anterior mandibular fracture using either 2.0 mm titanium miniplate or 2.4 mm titanium lag screw technique.
Materials and Methods
A total of 30 patients were managed by open reduction and internal fixation utilizing the miniplate and lag screw technique for fractures of anterior mandible. The patients were randomly divided into two groups. Group I: (15 patients) were treated with Leibinger, 2.0 mm titanium mini plates system with self-tapping screws and Group II: (15 patients) were treated with 2.4 mm cortical lag screw (Synthes). Intraoperatively duration of surgery was measured from the time incision was placed till the closure of wound. Subsequent follow up was done at 3, 6, 12, 24 weeks, postoperatively. During every follow up, patients were assessed clinically for malocclusion, neurosensory deficit, biting efficiency, implant failure, mal-union/non-union. Pre and postoperative radiographs were taken to assess the gap between fracture segments. Results were evaluated using Chi square and the unpaired t test.
In our study, the mean duration of surgery (hours) was 1.97 ± 0.52 for group I and 1.26 ± 0.55 for group II. The difference was found to be statistically significant (p value 0.001). i.e. more time was taken in case of surgery with mini-plates when compared to the lag screw. Short surgical procedure reduces the incidence of infectious complications, which significantly lowers the financial burden. The mean post-operative radiographic distance between all measuring points were considerably more in case of mini-plate group as compared to lag screw group. Lag screw group showed faster improvement in terms of biting efficiency as compared to mini-plate group which showed a tendency to masticate only medium hard food items by 24 weeks. In both groups, no postoperative malocclusion was noted. In initial weeks, neurosensory deficit was seen more in mini-plate group as compared to lag screw group but after six weeks all patients showed improvement in neurosensory function without any permanent nerve damage.
According to this prospective study, rigid internal fixation provided by lag screw technique for anterior mandibular fracture offers several advantages over conventional bone plating. It is an excellent means of achieving rapid and safe fixation which is followed by primary bone healing in anterior mandibular fractures, without any major complications.
Mandibular fractures; Miniplates; Compression osteosynthesis; Lag screw technique
p53, a member of the innate immune system, is triggered under stress to induce cell growth arrest and apoptosis. Thus, p53 is an important target for viruses, as efficient infection depends on modulation of the host apoptotic machinery. This study focuses on how rotaviruses manipulate intricate p53 signaling for their advantage. Analysis of p53 expression revealed degradation of p53 during initial stages of rotavirus infection. However, in nonstructural protein-1 (NSP1) mutant strain A5-16, p53 degradation was not observed, suggesting a role of NSP1 in this process. This function of NSP1 was independent of its interferon or phosphatidylinositol 3-kinase (PI3K)/AKT modulation activity since p53 degradation was observed in Vero cells as well as in the presence of PI3K inhibitor. p53 transcript levels remained the same in SA11-infected cells (at 2 to 14 h postinfection), but p53 protein was stabilized only in the presence of MG132, suggesting a posttranslational process. NSP1 interacted with the DNA binding domain of p53, resulting in ubiquitination and proteasomal degradation of p53. Degradation of p53 during initial stages of infection inhibited apoptosis, as the proapoptotic genes PUMA and Bax were downregulated. During late viral infection, when progeny dissemination is the main objective, the NSP1-p53 interaction was diminished, resulting in restoration of the p53 level, with initiation of proapoptotic signaling ensuing. Overall results highlight the multiple strategies evolved by NSP1 to combat the host immune response.
To assess adherence patterns to the UK National Institute of Health and Clinical Excellence (NICE) guidelines on glaucoma management (2009) in a tertiary referral centre shared care setting and in a district general hospital (DGH) setting.
We performed a retrospective case note analysis of 200 patients from two centres between January and June 2010. The two centres involved were a consultant-guided teaching hospital optometry-led shared care setting (setting 1) and a consultant-led DGH clinic setting (setting 2). The main outcome measures were compliance with eight of the main NICE guidelines on glaucoma diagnosis and management (2009).
Both centres showed good adherence to the guidelines regarding the choice of initial treatment (96% vs 100%, settings 1 and 2, respectively) and arranging appropriate monitoring intervals (92% vs 86%). However, significant differences were seen when assessing whether an optic disc image was obtained at the initial visit (74% vs 10%), whether an appropriate initial assessment was performed (96% vs 58%), whether patients' review interval complied with the NICE guidance regardless of hospital cancellations (92% vs 66%), and whether concordance with medication was checked (88% vs 24%) (settings 1 and 2, respectively, P<0.01—Fisher's exact test).
Our study provides evidence to suggest that a hospital-based shared care service with trained optometrists using assessment sheets compares favourably to non-specialist glaucoma care delivered by ophthalmologists.
glaucoma; shared care; optometry
Intra-abdominal hypertension (IAH) is being increasingly reported in patients with severe acute pancreatitis (SAP) with worsened outcomes. The present study was undertaken to evaluate intra-abdominal pressure (IAP) as a marker of severity in the entire spectrum of acute pancreatitis and to ascertain the relationship between IAP and development of complications in patients with SAP.
IAP was measured via the transvesical route by measurements performed at admission, once after controlling pain and then every 4 hours. Data were collected on the length of the hospital stay, the development of systemic inflammatory response syndrome (SIRS), multiorgan failure, the extent of necrosis, the presence of infection, pleural effusion, and mortality.
In total, 40 patients were enrolled and followed up for 30 days. The development of IAH was exclusively associated with SAP with an APACHE II score ≥8 and/or persistent SIRS, identifying all patients who were going to develop abdominal compartment syndrome (ACS). The presence of ACS was associated with a significantly increased extent of pancreatic necrosis, multiple organ failure, and mortality. The mean admission IAP value did not differ significantly from the value obtained after pain control or the maximum IAP measured in the first 5 days.
IAH is reliable marker of severe disease, and patients who manifest organ failure, persistent SIRS, or an Acute Physiology and Chronic health Evaluation II score ≥8 should be offered IAP surveillance. Severe pancreatitis is not a homogenous entity.
Intra-abdominal hypertension; Pancreatitis
Development of autoantibodies against coagulation factor VIII (FVIII) leads to a rare condition defined as acquired hemophilia (AH). If not diagnosed and treated early, AH may be associated with high mortality and morbidity. A 65-year-old woman presented with history of macrohematuria, acute renal failure, cardiogenic shock, and acute respiratory failure. Blood investigation revealed azotemia, prolonged activated partial thromboplastin time (aPTT), coagulation FVIII level of <1%, and presence of FVIII inhibitor. Echocardiography showed global hypokinesia and ultrasonography and computed tomography (CT) revealed bilateral hydroureteronephrosis. The final diagnosis was acquired hemophilia A, complicated by acute obstructive renal failure and cardiorenal syndrome (CRS) type 3. Patient was managed with mechanical ventilation, heparin-free hemodialysis, negative fluid balance, recombinant activated factor VII, and prednisolone. Hematuria was relieved, renal function improved, and cardiac function showed improvement on repeat echocardiography. Patient was discharged on prednisolone with subsequent follow ups.
Acquired hemophilia; cardiorenal syndrome; factor VIII inhibitor; recombinant activated factor VII
Bacteremia frequently occurs after treatment procedures such as extractions, scaling, root planing, periodontal surgery. There is currently significant interest in the possibility that bacteremia with oral bacteria may play role in pathogenesis of atherosclerosis. There are well-conducted studies that have determined the frequency of passage of periodontal microorganisms to the bloodstream after periodontal treatment. There is scarce information related to the incidence of periodontopathic microorganisms during bacteremia induced by this procedure.
The aim of this study was to establish the frequency of passage of periodontopathic microorganisms in peripheric blood after scaling and root planing in patients with periodontitis.
Materials and Methods:
Forty subjects with chronic periodontitis were included in the study. Blood samples were drawn from each patient at following intervals pre-treatment i.e., before SRP (P1), immediately after SRP (P2), and 30 minutes after SRP (P3). Following SRP, blood samples were analyzed for following microorganisms: Porphyromonasgingivalis, Tannerella. forysthus, Eikenellanella. corrodens, Campylobacter species, Micromonas. micros, and Prevotella. intermedia.
Statistical Analysis Used:
Bacteremia was found in 70% (28/40) immediately after SRP and after 30 min, it was reduced to 25% (10/40) and 7.5% (3/40) presented bacteremia before SRP.
It was concluded that bacteremia frequently occurs immediately after SRP with P. gingivalis showing the highest frequency in blood.
Bacteremia; P. gingivalis; scaling and root planing
Herpes genitalis, caused by HSV-2, is an incurable genital ulcerative disease transmitted by sexual intercourse. The virus establishes life-long latency in sacral root ganglia and reported to have synergistic relationship with HIV-1 transmission. Till date no effective vaccine is available, while the existing therapy frequently yielded drug resistance, toxicity and treatment failure. Thus, there is a pressing need for non-nucleotide antiviral agent from traditional source. Based on ethnomedicinal use we have isolated a compound 7-methoxy-1-methyl-4,9-dihydro-3H-pyrido[3,4-b]indole (HM) from the traditional herb Ophiorrhiza nicobarica Balkr, and evaluated its efficacy on isolates of HSV-2 in vitro and in vivo. The cytotoxicity (CC50), effective concentrations (EC50) and the mode of action of HM was determined by MTT, plaque reduction, time-of-addition, immunofluorescence (IFA), Western blot, qRT-PCR, EMSA, supershift and co-immunoprecipitation assays; while the in vivo toxicity and efficacy was evaluated in BALB/c mice. The results revealed that HM possesses significant anti-HSV-2 activity with EC50 of 1.1-2.8 µg/ml, and selectivity index of >20. The time kinetics and IFA demonstrated that HM dose dependently inhibited 50-99% of HSV-2 infection at 1.5-5.0 µg/ml at 2-4 h post-infection. Further, HM was unable to inhibit viral attachment or penetration and had no synergistic interaction with acyclovir. Moreover, Western blot and qRT-PCR assays demonstrated that HM suppressed viral IE gene expression, while the EMSA and co-immunoprecipitation studies showed that HM interfered with the recruitment of LSD-1 by HCF-1. The in vivo studies revealed that HM at its virucidal concentration was nontoxic and reduced virus yield in the brain of HSV-2 infected mice in a concentration dependent manner, compared to vaginal tissues. Thus, our results suggest that HM can serve as a prototype to develop non-nucleotide antiviral lead targeting the viral IE transcription for the management of HSV-2 infections.
The G:C reverse Watson–Crick (W:W trans) base pair, also known as Levitt base pair in the context of tRNAs, is a structurally and functionally important base pair that contributes to tertiary interactions joining distant domains in functional RNA molecules and also participates in metabolite binding in riboswitches. We previously indicated that the isolated G:C W:W trans base pair is a rather unstable geometry, and that dicationic metal binding to the Guanine base or posttranscriptional modification of the Guanine can increase its stability. Herein, we extend our survey and report on other H-bonding interactions that can increase the stability of this base pair. To this aim, we performed a bioinformatics search of the PDB to locate all the occurencies of G:C trans base pairs. Interestingly, 66% of the G:C trans base pairs in the PDB are engaged in additional H-bonding interactions with other bases, the RNA backbone or structured water molecules. High level quantum mechanical calculations on a data set of representative crystal structures were performed to shed light on the structural stability and energetics of the various crystallographic motifs. This analysis was extended to the binding of the preQ1 metabolite to a preQ1-II riboswitch.