Rhizomelic chondrodysplasia is a form chondrodysplasia punctata (see this term), a group of diseases in which the common characteristic is calcifications near joints at birth. Prevalence of the rhizomelic type is estimated at 1 in 100,000. Rhizomelic chondrodysplasia is associated with shortness of the femur and humerus, vertebral disorders, cataract, cutaneous lesions and severe intellectual deficit. The disease is caused by defective peroxisome metabolism and is transmitted in an autosomal recessive manner. The majority of patients affected by this disease carry mutations in the PEX7 gene (6q21-q22.2) encoding the peroxisomal targeting signal 2 receptor which plays an important role in peroxisomal protein import. Other cases are due to mutations in the GNPAT gene (1q42) encoding dihydroxyacetone phosphate acyltransferase or in the AGPSgene (2q31) encoding peroxisomal alkyldihydroxyacetonephosphate synthase. Diagnosis is based on clinical and radiologic findings and can be confirmed by molecular analysis. The principle differential diagnosis is Zellweger syndrome (see this term). Prenatal diagnosis is feasible when the causative mutation has already been identified in the family. There is no specific treatment for the enzyme defect. Rhizomelic chondrodysplasia has a severe prognosis with death generally occurring during the first decade of life, mainly due to respiratory complications.
Last update: November 2008