Preetha Tilak

Androgen insensitivity syndrome: ten years of our experience.

Abnormalities of secondary sexual differentiation manifest in varying degrees depending upon the severity of the underlying cause. Primary amenorrhea in phenotypic females is caused by several different factors, including hormonal imbalance, nutritional deficiency and sex differentiation abnormalities. Androgen insensitivity syndrome (AIS) accounts for a large proportion of such cases in phenotypic females but genetically male individuals. Over the past 10 years, we have collected data related to androgen insensitivity from more than 150 cases. The research identified several important but neglected facts about this syndrome; including the identification of mutations in 39% of the cases and the establishment of the cause of pathogenesis in 60% of them. The most intriguing facts were uncovered in relation to late presentation of the AIS cases, little awareness among patients and family members, no consensus on the age of performing gonadectomy, and reluctance of the patients to undergo recommended surgery. These issues need immediate attention to improve healthcare and management of AIS cases. This article summarizes our observations about AIS with an aim to spread awareness among patients and clinicians.

Cytogenetic Analysis in Down Syndrome

Abstract Clinically diagnosed Down syndrome cases are referred for karyotyping and counseling. Data on incidence patterns of the 3 cytogenetic types of Down syndrome from the cases seen during the duration of 35 years is presented. Chromosomes were examined after G-banded technique of peripheral lymphocyte cultures. For each patient, in addition to the detailed case history in the proforma 15 metaphases were examined and in cases of mosaicism, the count was increased to 25 to 50 metaphases for analysis. A total of 874 cases were confirmed to have the karyotype of Down syndrome. 509 were male probands (58.24%) and 365 (41.76%) were female cases. The most common was free trisomy 21 in 759 (86.9%), translocation in 77 (8.8%) and mosaicism in 38 (4.3%) cases. Robertsonian translocation 14;21 (48;62.34%) was prevalent among the 77 cases with translocation and the remaining 29 cases had the translocation of chromosome 21 either to chromosomes 1 (1) or 15(2) or 21 (26). The sex ratio has indicated the prevalence of the males for the total sample (1.41:1) (509: 365) as well as for the 3 basic cytogenetic types of DS. Included in the male trisomy 21 are the 2 cases with Klinefelter syndrome (KFS)(48,XXY+21) and one with de novo Robertsonian translocation between chromosomes 13 and 14.

Effect of Reciprocal Translocations on Phenotypic Abnormalities

Abstract The chromosomal disorders make a significant contribution to human mortality and morbidity. Karyotyping allows the identification of various chromosomes involved in a rearrangement. Chromosomal aberrations occur in approximately 1 in 200 live – born infants and the incidence of reciprocal translocations (rcpts) occur as 1/500 live births. Balanced reciprocal translocations can lead to a variety of unbalanced products. In this study, undertaken at the Division of Human Genetics of the Department of Anatomy of St. John’s Medical College, Bangalore, 58 cases of reciprocal translocations were collected from the existing data and the results were compiled. The most important observations noted in this study were: 1. The frequency of rcpts was 4.2% among the chromosomal abnormalities identified in the laboratory. 2. The common chromosomes involved in rcpts were chromosomes 1,2,3,5,7,9 and 22. The comparative site of the breakpoints showed preference at 1q, 2p, 5q, 3q, 7p and 9p. 3. Comparison between the distribution of parental carrier status and the cases, which were de novo, was explained. Parental carrier status was seen in 18 cases (31.03%) and de novo status was seen in the remaining 40 cases (68.97%). 4. Determination of the sex-ratio and the incidence among the affected male/female cases was 1.14:1 showing predictable maternal carrier predominance. 5. A higher clinical correlation between Bad Obstetric History and MR/MCA to various types of rcpts were identified in these individuals. All these results were correlated and serve as a basis for predictive genetic counseling to these affected individuals and provide clues to the positioning of important genes that may be responsible for human malformations, thus indicating important developmental genes being disrupted during segregation. This study has highlighted for the first time, a profile on rcpts in the Indian population.

A novel mutation 5’ to the HMG box of theSRY gene in a case of Swyer syndrome

We describe a novel mutation in the coding region of theSRY gene in a 46, XY female with Swyer syndrome. Analysis ofSRY was carried out by direct sequencing of a 780-bp PCR product that included theSRY open reading frame (ORF). This revealed the presence of a point mutation, ins 108A, in the coding region 5’ to the HMG box which results in a frame shift and premature termination of the encoded protein. No other mutation was found in theSRY ORF. We infer that sex reversal in this individual is a result of this insertion. In none of the 13 other 46, XY females that were studied was a mutation detected inSRY, confirming earlier findings that most cases of XY femaleness are due to causes other than mutation inSRY. These observations and those of others are discussed in relation to the aetiology of XY sex reversal.

45,X/47,X,i(X)(q10),i(X)(q10)/46,X,i(X)(q10) Isochromosome Xq in Mosaic Turner syndrome

Abstract A 17-year old female has been referred for karyotyping and genetic counseling. Proband had primary amenorrhea, short stature and poorly developed secondary sexual characteristics. Ultrasound scanning showed hypoplastic uterus and gonadal dysgensis. Chromosomal analysis revealed the mosaic status for the isochromosome formation in the long arm of X, i(Xq). Proband had 3 cell lines. Her karyotype: 45,X(4%)/ 47,X, i(X)(q10), i(X)(q10)(8%)/ 46,X, i(X)(q10)(88%). Proband has expressed X numerical anomaly for the constitutional X structural anomaly. Proband and family were counseled about education, career, appropriate medical management and hormonal therapy.

Spectrum of mutations in the SMPD1 gene in Asian Indian patients with acid sphingomyelinase deficient Niemann-Pick disease

Prajnya Ranganath, Divya Matta, Gandham SriLakshmi Bhavani, Savita Wangnekar, Jamal Mohammed Nurul Jain, Ishwar C. Verma, Madhulika Kabra, Ratna D. Puri, Sumita Danda, Neerja Gupta, Katta M. Girisha, Vaikom H. Sankar, Siddaramappa J. Patil, Akella Radha Rama Devi, Meenakshi Bhat, Kalpana Gowrishankar, Kausik Mandal, Shagun Aggarwal, Parag Mohan Tamhankar, Preetha Tilak, Shubha R. Phadke, and Ashwin Dalal

Spectrum of SMPD1 mutations in Asian-Indian patients with acid sphingomyelinase (ASM)-deficient Niemann-Pick disease.

Acid sphingomyelinase (ASM)‐deficient Niemann–Pick disease is an autosomal recessive lysosomal storage disorder caused by biallelic mutations in the SMPD1 gene. To date, around 185 mutations have been reported in patients with ASM‐deficient NPD world‐wide, but the mutation spectrum of this disease in India has not yet been reported. The aim of this study was to ascertain the mutation profile in Indian patients with ASM‐deficient NPD. We sequenced SMPD1 in 60 unrelated families affected with ASM‐deficient NPD. A total of 45 distinct pathogenic sequence variants were found, of which 14 were known and 31 were novel. The variants included 30 missense, 4 nonsense, and 9 frameshift (7 single base deletions and 2 single base insertions) mutations, 1 indel, and 1 intronic duplication. The pathogenicity of the novel mutations was inferred with the help of the mutation prediction software MutationTaster, SIFT, Polyphen‐2, PROVEAN, and HANSA. The effects of the identified sequence variants on the protein structure were studied using the structure modeled with the help of the SWISS‐MODEL workspace program. The p. (Arg542*) (c.1624C>T) mutation was the most commonly identified mutation, found in 22% (26 out of 120) of the alleles tested, but haplotype analysis for this mutation did not identify a founder effect for the Indian population. To the best of our knowledge, this is the largest study on mutation analysis of patients with ASM‐deficient Niemann–Pick disease reported in literature and also the first study on the SMPD1 gene mutation spectrum in India.

Congenital Heart Defects and Chromosomal Abnormality

Abstract Chromosomal abnormality is one of the causal factors in the formation of the congenital heart defects. 65 patients (33 male and 32 female) with heart defects were referred for karyotyping and counseling. Chromosomal abnormalities were detected in 27 (41.5%) and 38 had a normal karyotype. Numerical abnormality was found in 21 (77.8%) and structural in 6 (22.2%), numerical was detected in 14 females and 7 males, and structural in 4 female and 2 male patients. Numerical abnormality was one with 47,XX+13; 2 with 45,X and 18 with 47,XX+21 (11) or 47,XY+21(7). Structural abnormality was derivative 9 in 2, deletion 11q, derivative 14, Robertsonian translocation between 14 and 21 and ring 18 mosaicism in one each. Parental origin of the structural abnormality revealed that two were maternal and one was paternal. In the present study, association could be detected between chromosome 21 and the female probands with chromosomal abnormality and heart defects.

Association of the Chr omosomal Breakpoints in Reciprocal Translocation

Abstract Reciprocal translocation involves break and exchange of the chromosomal segments between two non-homologous chromosomes. It is aimed to report the association between the breakpoints in the chromosomes and the clinical conditions and the sex of the carrier. The present study has analyzed the data from 42 carriers and there were 17 male and 25 female carriers. For the total sample, it was observed that 25 were in bad obstetric history; 25 chromosomes belonged to C group; chromosome 1 was involved 6 times with 2,3,9,14,15; the formation of the translocation between the long arms (q;q) was in 21 and the breakpoints in the long arm were 59. Bad obstetric history was associated to C group chromosomes in 15 and the long arm combinations were seen in 12 and the breakpoints in it were 29. In the female, 15 with bad obstetric history were carriers; C group was seen in 18 and in 11 it showed the association to bad obstetric history; the long arm combination was noted in 13 and in 8 it was in bad obstetric history; breakpoints in the long arm were 37 and 22 times it was in bad obstetric history and the translocation between 15q and 22q were associated to bad obstetric history. In the present study, the chromosomes and its arms and breakpoints and the clinical conditions were associated to female and bad obstetric history.

Analysis of the Chromosomal Deletions

Abstract Deletion involves loss of part of a chromosome resulting in monosomy for that segment of chromosome. In this paper, a data profile on the detected chromosomal deletions and its association to the phenotype is reported. Data was obtained from 55 probands referred to Division of Human Genetics, from 1974 to 2007. Chromosomal preparations included modified leucocyte microculture method. Deletions were observed in 14 autosomes (2,3,4,5,6,8,9,11,13,15,16,17,18,22) and in X and Y. Deletion in the autosomes was seen in 37 and in X in 13. Deletion, as single cell line was identified in 32 and in mosaic status in 23. Deletion in the long arm of chromosomes was seen in 40 (72.7%) and in short arm in 15 (27.3%) and the break points could be pinpointed in 36. Male to female sex ratio was 1.1:1 (29:26). In 29 males deletion in the autosomes was observed in 24 and in 26 females deletion in autosomes & in X was of equal occurrence (13/26). Chromosomes with deletion seen in both sexes were 3,5,8,9,11,15,18. Deletions were found to be ‘de novo’ in 9. Deletion was associated to multiple congenital abnormality and or mental retardation (26), amenorrhea (12), bad obstetric history (13) and abnormality in the skeletal (15) and genital systems (15). The analyzed chromosomal deletions and the loss of the chromosomal segments seemed to be associated to a range of clinical conditions and birth defects. The present study, may be for the first time reporting the data on deletion from India.