Not lost to follow-up: A rare case of CHILD syndrome in a boy reappears

Male CDPX2 patient with EBP mosaicism and asymmetrically lateralized skin lesions with strict midline demarcation

X-linked dominant chondrodysplasia punctata (Conradi-Hunermann-Happle syndrome, CDPX2) caused by mutations in the emopamil-binding protein (EBP) gene and congenital hemidysplasia with ichthyosiform nevus and limb defects (CHILD) syndrome caused by mutation in the NAD(P)H steroid dehydrogenase-like (NSDHL) gene are rare, typically male lethal disorders. CDPX2 skin lesions are characterized by transient severe congenital ichthyosis following the lines of Blaschko, whereas in CHILD syndrome, the lesions show striking lateralization. Here, we report a male CDPX2 patient with postzygotic mosaicism of the EBP gene presenting with lateralized skin lesions with strict midline demarcation as seen in CHILD syndrome (although this diagnosis was ruled out based on analysis of NSDHL), but also partly distributed along Blaschko's lines as seen in CDPX2. The lesions resolved within a few months, but the patient had other abnormalities, including shortening of the limbs, epiphyseal stippling, and forearm asymmetry; he also had problems with respiration and feeding in the first 4 years after birth. Kyphoscoliosis with dysplastic vertebral bodies progressed rapidly and required posterior spinal fusion surgery at 6 years old. These findings provide insights into the pathophysiology of CDPX2 and the mechanism of asymmetric lesion formation during development.