Case Report - Down syndrome with Fragment X - A case Report

This article reports a case of four-month-old female infant referred to Division of Human Genetics, St. Johns' Medical College, for karyotyping with suspicion of Down syndrome. On karyotyping all analysed spreads showed trisomy 21 but a few spreads (6.66%) showed fragment X. X was broken at the centromere and both short and long arms were present in the spread. GTG bands of the two fragments correlated with the normal X counter parts. The mechanism behind isochromosome formation is discussed. Thus, this case is free trisomy 21 for Down syndrome and a mosaic for the X structural anomaly

The enigma of a subluxated globe

Spontaneous globe subluxation (SGS) is an uncommon condition wherein the equator of the globe protrudes anteriorly beyond the eyelid aperture causing severe lagophthalmos, proptosis and exposure keratopathy. SGS can lead to an emotional disturbance leading to anxiety and fear, thereby affecting one's quality of life. The patients might often be able to reduce the globe on their own, but permanent measures must be taken to prevent recurrence and vision-threatening sequelae of SGS. We present this case due to its rarity and to highlight the importance of a simple, cost-effective and cosmetically acceptable bilateral tarsorrhaphy in management of SGS

A novel human sex-determining gene linked to Xp11.21-11.23

Context: The molecular basis for about 70-80% of 46,XY sex-reversed females remains unexplained, because they carry normal copies of the genes (SRY, SOX9, DAX1, DMRT, SF1, WT1) involved in sex determination pathway. Objective: The objective of this study is to map the chromosomal locus responsible for an unexplained sex-reversed phenotype. Design: The study implemented a genome-wide scan using families with multiple sex-reversed individuals. Setting: The patients, along with the family members, were selected from different hospitals/reproductive centers. Participants: Sex-reversed individuals and their siblings and parents participated in the study. Main Outcome Measures: Identification of the chromosomal locus responsible for sex reversal in these families and sequence analysis of candidate genes were the main outcome measures. Results: Parametric linkage analysis revealed a maximum two-point LOD score of 5.70 with marker DXS991 (Xp11.21) and 4.57 with marker DXS1039 (Xp11.23-Xp11.22), and a multipoint LOD score of 5.77 with marker DXS991 and 5.22 with marker DXS1039. The two markers (DXS991 and DXS1039) with highest LOD score span approximately 3.41 cM (75.79-79.2 cM) on the short arm of the X-chromosome. Conclusion: Our findings provide evidence for a major susceptibility locus for sex reversal/gonadal dysgenesis on the short arm of the X-chromosome (Xp11.21-11.23). Furthermore, molecular exploration of the expression of candidate genes in the embryonic gonad/gonadal ridge will help in the identification of the underlying gene for sex reversal