X-linked dominant chondrodysplasia Chassaing-Lacombe type is a rare genetic bone disorder characterized by chondrodysplasia, intrauterine growth retardation (IUGR), hydrocephaly and facial dysmorphism in the affected males. Prevalence is unknown. To date, 10 patients (4 males and 6 females) in a single family have been reported through 4 generations. Three male fetuses were diagnosed prenatally on ultrasonography (skeletal abnormalities and hydrocephaly) leading to termination of the pregnancies. The fourth affected male died at 6 days of life. The disease is severe and probably lethal in males, in whom the clinical picture includes short hands, brachydactyly, hydrocephaly and facial dysmorphism, including frontal bossing, low-set ears, short flat nose and microphthalmia. Other signs may include cerebellar hypoplasia and hyperkeratotic skin. X-rays show severe platyspondyly due to delayed ossification of the vertebrae, thin ribs, moderate shortening of the long bones, hypoplastic iliac wings, poorly ossified pubis, brachydactyly of the fingers and/or toes with cupped metacarpals, metatarsals, and phalanges and hypoplastic square calcaneus. The clinical picture in females is less severe and comprises short stature (128-151 cm), rhizomelic shortening of the limbs, short hands, brachymesophalangia of the 3rd and 4th toes, and may be associated with body asymmetry and mild cognitive impairment. X-linked dominant chondrodysplasia Chassaing-Lacombe type is due to a mutation in the histone deacetylase 6 HDAC6 gene (Xp11.3-q13.1) that causes a nucleotide substitution in the 3' untranslated region (UTR) of the HDAC6 transcript. This mutation lies in the seed sequence of microRNA-433 (hsa-miR-433) and abolishes the post-transcriptional regulation of HDAC6 expression by hsa-miR-433, resulting in the overexpression of the HDAC6 protein. Inheritance is X-linked dominant.
Last update: February 2011