Autopsy findings of a 37-year-old man with a complex mosaic karyotype involving del(18p), monosomy 13, and trisomy 20.

We report on the autopsy findings of a 37-year-old man with a complex karyotype (mos46,XY,del(18)(p11.1)[14]/46,XY, -13, del (18)(p11.1), +20[8]/47,XY,del(18)(p11.1), +20[8]). He was known to be blind, non-ambulatory, have severe mental retardation, and a seizure disorder. External physical findings at the time of autopsy included micrognathia, short stubby fingers, and rocker bottom feet. Left lobe dominance of the liver and mislocation of the ileocecal junction and appendix were noted on internal examination. The brain was small (700 g) and poorly developed. Microscopically it showed an absence of neurons in the olivary and dentate nuclei, absence of Purkinje cells in the cerebellum, severe depletion of internal granular cells in the cerebellum, and cerebellar dysplasia. Fat infiltration was noted in an unusual distribution in several organs including a pattern in the heart consistent with arrythmogenic right ventricular dysplasia (ARVD). Findings of this mosaic chromosomal karyotype have not been previously described. This report will discuss this individuals physical findings and their relation to similar monochromosomal aberrations.

Prenatal detection of an interstitial deletion in 4p15 in a fetus with an increased nuchal skin fold measurement.

OBJECTIVES: The detection of an increased nuchal translucency (NT) or nuchal fold (NF) measurement is associated with an increased risk of common aneuploidies. Only rarely is it associated with other types of chromosome abnormalities. We report the prenatal finding of an increased NF in a fetus with an interstitial 4p deletion. METHODS: Standard karyotype analysis was followed by FISH with research generated BAC probes to precisely map the 4p deletion. RESULTS: The karyotype of the fetus was determined to be 46,XX,del(4)(p15.2p16.1) by G-banding analysis and was refined to 46,XX,del(4) (p15.1p15.32) after FISH analysis. The breakpoints were narrowed to 150 kb regions on each side. The deletion is approximately 14.5 Mb, containing approximately 47 genes. CONCLUSIONS: We report a case of an increased NF measurement associated with a 4p deletion. A literature review revealed a previous case of a 4p deletion in a fetus with an increased NT. Since chromosome deletions are rarely associated with an increased NT or NF, we believe it is significant that a 4p deletion has now been found in two unrelated cases. We mapped the deletion with BAC probes, generating a list of possible candidate genes involved in the pathogenesis of increased nuchal skin folds.

Reevaluating confined placental mosaicism.

Chromosomal mosaicism was found in 38 of 4,000 chorionic villus samples examined from 1998 to 2003. A small fraction of these (5/38) were confirmed as true mosaics by analysis of amniotic fluid. Twenty-nine cases that fit the definition of confined placental mosaicism were followed with clinical and cytogenetic analysis throughout the pregnancy, at birth and in a few cases into infancy. This was done to determine the prognostic interpretation of prenatal cytogenetic results from multiple specimens in a single pregnancy and thus allow for reevaluation of the genetic counseling. In 2 of these 29 cases, low-level mosaicism was found in the neonate, and in 1 of these the chromosome abnormality is probably the cause of the resulting minor phenotypic abnormalities. Families face unique difficulties when confined placental mosaicism is the prenatal diagnosis, and it is extremely important that the counseling they receive takes into consideration the unlikely possibility of the placental abnormality appearing in fetal tissues.