De novo satellited 21q associated with corpus callosum dysgenesis, colpocephaly, a concealed penis, congenital heart defects, and developmental delay

De novo satellited 21q associated with corpus callosum dysgenesis, colpocephaly, a concealed penis, congenital heart defects, and developmental delay: We present clinical and cytogenetic data on an infant with de novo satellited 21 q. A 3-month-old boy was found to have microcephaly, developmental delay, hypertelorism, down-slanting palpebral fissures, large low-set ears, a prominent nose, a broad philtrum, a concealed penis, interventricular septal defects, corpus callosum dysgenesis, colpocephaly, ventriculomegaly, and a de novo karyotype of 46,XY,21qs. Standard Ag-NOR staining and FISH studies confirmed a satellite and a deletion on the long arm of a chromosome 21. Quantitative-fluorescent polymerase chain reaction using the polymorphic small tandem repeat markers specific for chromosome 21 determined a maternal origin of the deletion and the breakpoint between D21S156 (21q22.1) (present) and D21S53 (21q22.3) (absent), centromeric to the known minimal holoprosencephaly critical region, D21S13-21qter. The present case provides evidence of the correlation of a distal region of chromosome 21 to the phenotypic effects of monosomy 21.