Greenberg dysplasia (HEM) and lethal X linked dominant Conradi-Hünermann chondrodysplasia punctata (CDPX2): presentation of two cases with overlapping phenotype.

H ydrops-ectopic calcification-motheaten (HEM) skeletal dysplasia is a rare lethal autosomal recessive skeletal dysplasia which is also known as Greenberg dysplasia. There are currently only seven published cases. X linked dominant chondrodysplasia punctata (Conradi–Hünermann syndrome) mainly affects females and is characterised by aberrant punctate calcification of cartilage or stippling of the epiphyses, mainly in the areas of the vertebral column, pelvis, and long bones. There is asymmetrical shortening of the long bones, patchy skin changes (follicular atrophoderma), ichthyosis, areas of alopecia, and cataracts. The severity varies from the a lethal form to a mild disease affecting adults who are sometimes diagnosed only after having an affected child. The variable pattern of presentation is probably related to random X inactivation, which may also explain the wide spectrum of severity. We report on a further case of HEM and a lethal case of X linked dominant chondrodysplasia punctata, and we highlight the similarities and differences between these two conditions, discussing the role of plasma/tissue sterol measurements in the differential diagnosis.