Dyggve-Melchior-Clausen syndrome

Dyggve-Melchior-Clausen syndrome is a rare inherited disorder in which the skeleton develops abnormally and the head stays small, usually together with intellectual disability. It was first reported in 1962 by Dyggve, Melchior and Clausen in a group of siblings whose parents were closely related, and at first it was mistaken for what is now called Morquio syndrome because of the patients' appearance and the mucopolysaccharides found in their urine. Affected people typically have short stature, a short trunk with a barrel-shaped chest, partial dislocation of the hips, knock-knees or bowed legs and stiff joints, and some have instability of the upper neck vertebrae that can press on the spinal cord. The condition results from changes in both copies of the DYM gene, which makes the protein dymeclin, and it follows an autosomal recessive pattern of inheritance. Treatment is symptomatic and supportive, including spinal stabilization or hip surgery where needed. Smith-McCort syndrome is a closely related disorder caused by changes in the same gene but without the small head and intellectual disability.