SMC, which was first described in 1958, is an autosomal recessive skeletal dysplasia. The disease bears similarity to Dyggve-Melchior-Clausen (DMC) syndrome except that patients with SMC have normal intelligence function, whereas patients with DMC have moderate to severe intellectual disabilities. The DMC gene is mapped to the 18q12-12.1 chromosomal region. SMC (OMIM: 607326) also mapped to this same region and as it turns out both conditions have mutations in the DYM gene. DMC results from mutations in the gene that results in loss of function, whereas in SMC, the mutation is a missense mutation resulting in residual DYM activity, thus a less severe phenotype. The gene codes for a novel protein known as Dymeclin, which is involved in Golgi organisation and intracellular trafficking.

Recently, another gene, RAB33B, which decreases the level of another Golgi protein that is involved in retrograde transport of Golgi vesicles, has been implicated in the pathogenesis of SMC.