X-linked dominant chondrodysplasia punctata (CDPX2) caused by single gene mosaicism in a male

X‐linked dominant chondrodysplasia punctata (CDPX2; Happle syndrome) is recognized almost exclusively in females, who display mosaic and asymmetric features, presumed to arise secondary to random X‐inactivation. CDPX2 results from mutation of an X‐linked gene coding for sterol‐Δ8‐Δ7 isomerase (emopamil binding protein). We describe a boy with clinical features of CDPX2 (including those presumed to arise usually secondary to functional mosaicism in females). Biochemical and molecular studies demonstrate that he is mosaic for a sterol‐Δ8‐Δ7 isomerase gene mutation. He is the first reported example of single gene mosaicism giving rise to CDPX2 in a male. © 2002 Wiley‐Liss, Inc.