Methyl-CpG-binding protein 2 gene mutations and its association with epilepsy: a single centre study from the Indian subcontinent

Rett syndrome (RTT) is an X-linked disorder caused by mutations in MECP2 in majority of cases. It is characterized by arrested development between 6 and 18 months of age, regression of acquired hand skills and speech, stereotypic hand movements, gait abnormalities and seizures. There are a very few studies in India which illustrates mutation spectrum in RTT. None of the studies have correlated seizures with the genotype. This study describes the phenotype and genotype spectrum in children with RTT syndrome and analyses the association of epilepsy with various clinical features and molecular findings. All children with RTT in our cohort had global developmental delay. Genetic diagnosis identified mutations of the MECP2 in all 25 children where RTT was suspected. We have identified point mutations in 20 patients, one insertion and four deletions by Sanger sequencing, namely c.1164_1207 (44 bp), c.1165_1207 (43 bp), c.1157_1197 (41 bp) del and c.1157_1188 (32 bp). Clinically, none of the patients with deletion had seizures. We identified one novel insertion variant c.337_338 (p.S113Ffs*9). All the deletions were located in the C-terminal region. Majority of the mutations (22/25) were identified in exon 4 which comprised of nonsense and missense types. Screening of hotspot mutations in exon 4 should be the first line evaluation in diagnosis of RTT. Molecular testing could help in specific management of seizures in RTT.

Novel mutations of the arylsulphatase B (ARSB) gene in Indian patients with mucopolysaccharidosis type VI.

Background & objectives: Mucopolysaccharidosis type VI (MPS VI) is a rare, autosomal recessive lysosomal storage disorder caused by deficient enzymatic activity of N-acetyl galactosamine-4-sulphatase resulting from mutations in the arylsulphatase B (ARSB) gene. The ARSB gene is located on chromosome 5q11-q13 and is composed of eight exons. More than hundred ARSB mutations have been reported so far, but the mutation spectrum of MPS VI in India is still unknown. Hence, the aim of the present study was to identify the mutational spectrum in patients with MPS VI in India and to study the genotype-phenotype association and functional outcomes of these mutations. Methods: Molecular characterization of the ARSB gene by Sanger sequencing was done for 15 patients (aged 15 months to 11 yr) who were enzymatically confirmed to have MPS VI. Age of onset, clinical progression and enzyme activity levels in each patient were studied to look for genotype-phenotype association. Haplotype analysis performed for unrelated patients with the recurring mutation W450C, was suggestive of a founder effect. Sequence and structural analyses of the ARSB protein using standard software were carried out to determine the impact of detected mutations on the function of the ARSB protein. Results: A total of 12 mutations were identified, of which nine were novel mutations namely, p.D53N, p.L98R, p.Y103SfsX9, p.W353X, p.H393R, p.F166fsX18, p.I220fsX5, p.W450L, and p.W450C, and three were known mutations (p.D54N, p.A237D and p.S320R). The nine novel sequence variants were confirmed not to be polymorphic variants by performing sequencing in 50 unaffected individuals from the same ethnic population. Interpretation & conclusions: Nine novel mutations were identified in MPS VI cases from India in the present study. The study also provides some insights into the genotype-phenotype association in MPS VI.

Neonatal Hearing Screening – Experience from a Tertiary Care Hospital in Southern India.

Objective: To implement a neonatal hearing screening program using automated auditory brainstem response audiometry in a tertiary care set-up and assess the prevalence of neonatal hearing loss. Design: Descriptive study. Setting: Tertiary care hospital in Southern India. Participants: 9448 babies born in the hospital over a period of 11 months. Intervention: The neonates were subjected to a two stage sequential screening using the BERAphone. Neonates suspected of hearing loss underwent confirmatory testing using auditory steady state response audiometry. In addition, serological testing for TORCH infections, and connexin 26 gene was done. Main outcome measures: Feasibility of the screening program, prevalence of neonatal hearing loss and risk factors found in association with neonatal hearing loss. Results: 164 babies were identified as suspected for hearing loss, but of which, only 58 visited the audiovestibular clinic. Among 45 babies who had confirmatory testing, 39 were confirmed to have hearing loss and were rehabilitated appropriately. 30 babies had one or more risk factors; 6 had evidence of TORCH infection and 1 had connexin 26 gene mutation. Conclusion: Neonatal hearing screening using BERAphone is a feasible service. The estimated prevalence of confirmed hearing loss was comparable to that in literature. Overcoming the large numbers of loss to follow-up proves to be a challenge in the implementation of such a program.

Clinical utility of multiplex ligation-dependent probe amplification technique in identification of aetiology of unexplained mental retardation: A study in 203 Indian patients.

Background & objectives: Developmental delay (DD)/mental retardation also described as intellectual disability (ID), is seen in 1-3 per cent of general population. Diagnosis continues to be a challenge at clinical level. With the advancement of new molecular cytogenetic techniques such as cytogenetic microarray (CMA), multiplex ligation-dependent probe amplification (MLPA) techniques, many microdeletion/microduplication syndromes with DD/ID are now delineated. MLPA technique can probe 40-50 genomic regions in a single reaction and is being used for evaluation of cases with DD/ID. In this study we evaluated the clinical utility of MLPA techniques with different probe sets to identify the aetiology of unexplained mental retardation in patients with ID/DD. Methods: A total of 203 randomly selected DD/ID cases with/without malformations were studied. MLPA probe sets for subtelomeric regions (P070/P036) and common microdeletions/microduplications (P245-A2) and X-chromosome (P106) were used. Positive cases with MLPA technique were confirmed using either fl uorescence in situ hybridization (FISH) or follow up confirmatory MLPA probe sets. Results: The overall detection rate was found to be 9.3 per cent (19 out of 203). The detection rates were 6.9 and 7.4 per cent for common microdeletion/microduplication and subtelomeric probe sets, respectively. No abnormality was detected with probe set for X-linked ID. The subtelomeric abnormalities detected included deletions of 1p36.33, 4p, 5p, 9p, 9q, 13q telomeric regions and duplication of 9pter. The deletions/duplications detected in non telomeric regions include regions for Prader Willi/Angelman regions, Williams syndrome, Smith Magenis syndrome and Velocardiofacial syndrome. Interpretation & conclusions: Our results show that the use of P245-A2 and P070/P036-E1 probes gives good diagnostic yield. Though MLPA cannot probe the whole genome like cytogenetic microarray, due to its ease and relative low cost it is an important technique for evaluation of cases with DD/ID.

Juvenile ankylosing spondylitis in Turner syndrome.

Juvenile ankylosing spondylitis (JAS) is a chronic autoimmune disorder which causes considerable morbidity when left untreated; it occurs predominantly in men. We describe an Asian Indian woman who had JAS with phenotypic features of Turner syndrome (TS) and was found to be a mosaic for 45, X/46, X, psu idic (X) (p11) by karyotyping and fluorescence in situ hybridization (FISH) studies of peripheral blood. The absence of Y chromosome material was confirmed by FISH. Haplo-insufficiency of the X chromosome can predispose to autoimmunity. To the best of our knowledge, this is the first report of JAS in association with mosaic Turner syndrome. This case highlights the possible effects of gene dosage in development of an autoimmune disease.

Tumour necrosis factor (TNF)-α-308 gene polymorphism in Indian patients with Takayasu’s arteritis - A pilot study.

Background & objectives: Tumour necrosis factor-alpha (TNF-α)- 308 promoter gene polymorphism has been shown to be associated with several autoimmune disorders and infections such as tuberculosis. There is no study on TNF-α gene polymorphism in Takayasu’s arteritis (TA) till date. We aimed to study this polymorphism in TA, a granulomatous vasculitis, probably triggered by Mycobacterium tuberculosis. Methods: TNF-α - 308 gene polymorphism was studied in 34 patients with TA and 39 healthy controls recruited from Christian Medical College, India. PCR was done followed by enzyme digestion. G and A polymorphisms were analysed. Occurrence of alleles in the disease group was compared with controls as well as with historical controls. Results: GG allele was most frequent in TA and in controls. GA allele was detected in four controls but only in one patient who was the oldest in the study group. AA polymorphism was detected in one control but not in TA. When compared with controls from other populations, it was found that our allelic frequency was similar to that in Japan as well as from USA with mixed population. However, predominantly Caucasian population studied from Netherlands, Germany and England, where TA is rare, had a higher frequency of A allele as compared to our controls. Interpretation & conclusions: Our preliminary results indicated that G allele at TNF-α - 308 was more common in TA patients and controls similar to that in other Indian as well as Japanese population. Compared to the western population, A allele was relatively less common in our study subjects.

Cri du chat syndrome: A series of five cases.

The cri du chat syndrome (CdCS) is a chromosomal deletion syndrome associated with a partial deletion of the short (p) arm of chromosome 5. We describe five children who were diagnosed to have CdCS by conventional cytogenetic analysis. The deletion was at 5p15 in four patients, whereas the fifth had a larger, more proximal deletion at 5p14. Fluorescence in situ hybridization (FISH) analysis confirmed the deletion of the CdCS critical region at 5p15.2. All five children had global developmental delay and dysmorphism with microcephaly. The other clinical features were variable. Since the clinical diagnosis of CdCS may not always be evident because of the phenotypic heterogeneity, cytogenetic analysis is necessary to establish the diagnosis and confirm that the deletion involves the CdCS critical region. This will enable early intervention which plays an important role in improving the outcome.

ATR-X syndrome in two siblings with a novel mutation (c.6718C>T mutation in exon 31).

ATR-X syndrome is an X-linked mental retardation syndrome characterized by mental retardation, alpha thalassaemia and distinct facial features which include microcephaly, frontal hair upsweep, epicanthic folds, small triangular nose, midface hypoplasia and carp-shaped mouth. Here we report two brothers with clinical features of ATR-X syndrome, in whom a novel missense (C>T) mutation was identified in exon 31 of the ATRX gene.

Kenny-Caffey syndrome.

Kenny-Caffey syndrome is a rare hereditary skeletal syndrome characterized by dysmorphic features, severe growth retardation, classical radiological changes and hypocalcemia with hypoparathyroidism at an early age. We report an 8-month-old girl child with Kenny-Caffey syndrome who had most of the features of the syndrome. Any child with hypocalcemia who has typical facial features should raise a suspicion of this syndrome.