We present prenatal diagnosis and molecular cytogenetic characterization of concomitant familial small supernumerary marker chromosome 4 [sSMC(4)] derived from 4q11.1–q12 and q13.2, and 5q13.2 microdeletion with no apparent phenotypic abnormality.
Materials and methods
A 32-year-old woman underwent amniocentesis at 21 weeks of gestation because of absent nasal bone on fetal ultrasound. Amniocentesis revealed a karyotype of 47,XX,+mar/46,XX. Array comparative genomic hybridization analysis on the cultured amniocytes revealed a 2.752-Mb duplication at 4q11–q12, a 1.949-Mb duplication at 4q13.2, and a 1.65-Mb deletion at 5q13.2. The woman underwent repeat amniocentesis at 24 weeks of gestation for molecular cytogenetic characterization. The phenotypically normal parents and their elder son underwent genetic analysis.
At repeat amniocentesis, interphase fluorescence in situ hybridization analysis on uncultured amniocytes revealed 79.25% (84/106) mosaicism for the sSMC(4), and metaphase fluorescence in situ hybridization analysis on cultured amniocytes revealed that all 20 cells examined (100%) had the sSMC(4). Polymorphic DNA marker analysis on uncultured amniocytes excluded uniparental disomy 4. The father had a karyotype of 47,XY,+mar/46,XY, and interphase fluorescence in situ hybridization revealed 2.91% (3/103) mosaicism for the sSMC(4) in his peripheral blood. The mother carried the 5q13.2 microdeletion. The elder son had a karyotype of 47,XY,+mar/ 46,XY with duplications of 4q11–q12 and 4q13.2. A 3105 g female baby was delivered at term with no apparent phenotypic abnormality.
Prenatal diagnosis of concomitant sSMC and microdeletion should raise a suspicion of familial inheritance.