Metaphyseal chondrodysplasias are skeletal diseases with variable expression, divided into several rare types with a few reported cases for each. Patients show a short-limbed dwarfism due to skeletal dysplasia at birth already, with short hands and varus deformation of lower limbs. Radiographs show metaphyseal anomalies more evident at knees. Epiphyses are round and enlarged already in infancy. These anomalies may be identical to those encountered in cartilage-hair hypoplasia McKusick type, but without hypotrichosis or immunodeficiency. Microscopic examination of the hair may nevertheless show a reduction in the diameter of the hair shaft. This disease has an autosomal recessive mode of inheritance. Authors identified 4 mutation-carrying alleles in the RMRP gene (RNA component of Mitochondrial RNA-Processing endoribonuclease) localized in 9p21-p12. These allele look like corresponding to different types of metaphyseal changes. Recessive metaphyseal dysplasia without hypotrichosis might be an allelic variant of McKusick cartilage-hair hypoplasia.
Last update: May 2004
- Dr Elisabeth ROBERT-GNANSIA