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Trisomy 16 is common in embryos and fetuses aborted early during development. Mosaicism for trisomy 16 is sometimes encountered during prenatal diagnosis, particularly with chorionic villi biopsy specimens, and, until recently, was thought to be confined to the placenta. However, recently, several liveborn infants with trisomy 16 mosaicism have been described. We report on an additional liveborn infant with trisomy 16 mosaicism and compare the clinical findings with those of the previously reported cases in an attempt to delineate a mosaic trisomy 16 syndrome. Cytogenetic analysis from our patient showed that there was a different proportion of abnormal cells in different tissues and that the anomaly was undetectable in blood lymphocyte cultures. This observation was consistent with some of the previous reports. DNA analysis of parents and child was carried out using a polymorphic dinucleotide marker that maps to the long arm of chromosome 16. This analysis showed that the extra chromosome 16 in the infant was maternal in origin and suggested that the nondisjunction was probably a first meiotic division error. Our results suggest that an investigation of multiple tissues is required before concluding that mosaicism is confined to the placenta. We conclude that a finding of trisomy 16 mosaicism at prenatal diagnosis should be regarded with extreme caution. This diagnosis may be associated with a highly variable phenotype that may occasionally be compatible with extrauterine life.

Marfan syndrome is a systemic disorder of the connective tissue inherited as an autosomal dominant trait. The disorder imparts significant morbidity and mortality. The etiology of the disorder remains elusive. A recent study localized the gene for Marfan syndrome on chromosome 15. We present data showing that marker DISS48 is genetically linked to Marfan syndrome. Pairwise linkage analysis gave a maximum lod (logarithm of odds) score of Z = 11.78 at 0 = 0.02. Furthermore our data suggest that the Marfan syndrome locus is possibly flanked on either side by DISS48 and DISS49.Marfan syndrome is an autosomal dominant disorder of the connective tissue, characterized by cardiovascular, musculoskeletal, ocular, and pulmonary abnormalities (1). This condition is estimated to have a prevalence of4-6 per 100,000 individuals, imparts significant morbidity, and if untreated, reduces significantly the life expectancy (2 tTo whom reprint requests should be addressed. 4486The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

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