Homozygous or compound heterozygous microdeletion of 15q13.3 region is a rare but clinically recognizable syndrome manifested by profound intellectual disability, muscular hypotonia, intractable seizures, and visual impairment. We identified a compound heterozygous 15q13.3 microdeletion in a 23-month-old girl with global developmental delay, generalized muscular hypotonia, and visual dysfunction. The larger deletion was approximately 1.28 Mb in size and contained seven genes including the TRPM1 and CHRNA7, while the smaller deletion was estimated to be 410 Kb in size and contained only CHRNA7. Compound heterozygous 15q13.3 microdeletion is extremely rare and to the best of our knowledge only two such patients have been reported in literature thus far. The findings in our patient suggest that the pathogenesis of visual dysfunction, which is a consistent finding in homozygous/compound heterozygous 15q13.3 microdeletion depends upon the size of microdeletion. Homozygous loss of TRPM1 likely causes retinal dysfunction while homozygous loss of CHRNA7 alone may lead to visual impairment by cortical mechanisms.
We report on the molecular detection of two microduplications involving chromosomes Xp21.1-Xp21.2 and 17p12 in a 35-year-old female with clinical phenotype of Charcot-MarieTooth disease type 1A (CMT1A) documented by chromosomal microarray analysis. The 17p12 microduplication was approximately 1.32 Mb in size and contained eleven genes including the peripheral myelin protein 22 (PMP22), while the Xp21.1-Xp21.2 microduplication was estimated to be 626 Kb in size and contained part of the dystrophin (DMD) gene. Constitutional interstitial microduplication of 17p12 segment encompassing the PMP22 gene has been reported in individuals with Charcot-Marie-Tooth disease type 1A. Defects in the DMD gene (deletion, duplication, or mutation) are associated with Duchenne and Becker muscular dystrophies (DMD and BMD). Combined microduplications of Xp21/DMD with 17p12/PMP22 are extremely rare with only one published report of a male patient with changes in both the DMD and PMP22 genes. Ó 2014 Production and hosting by Elsevier B.V. on behalf of Ain Shams University.
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