Revisiting metatropic dysplasia: presentation of a series of 19 novel patients and review of the literature.

Metatropic dysplasia (MD-OMIM: 156530 and 250600) is a rare chondrodysplasia characterized by short limbs with limitation and enlargement of joints and usually severe kyphoscoliosis, first described in 1893. Up until now, 81 other patients have been reported. The phenotypic variability of MD has led to a classification based on radiological anomalies dividing into three different types: a lethal autosomal recessive form, an autosomal recessive non-lethal form and a non-lethal autosomal dominant form with less severe radiographs manifestations and a better clinical outcome. Here, we report on clinical and radiological features of 19 novel MD patients. We describe new radiological features, including precocious calcification of hyoid and cricoid cartilage, irregular and squared-off calcaneal bones and severe hypoplasia of the anterior portion of first cervical vertebrae. In addition, the observation of an overlap between the autosomal recessive non-lethal form and the non-lethal autosomal dominant form, the rarity of sibship recurrences and the observation of vertical transmissions of MD in the literature argue in favor of an autosomal dominant mode of inheritance for all MD types. This hypothesis is reinforced by the use of the statistical single ascertainment method that rejects the hypothesis of an autosomal recessive mode of inheritance responsible for MD. Therefore, we propose that recurrence in sibs is due to gonadal mosaicism. Copyright 2008 Wiley-Liss, Inc.