Pycnodysostosis: Clinical and genetic diagnosis

Pycnodysostosis (OMIM #265800), also known as osteochondrodysplasia or Maroteaux-Lamy syndrome, is a lysosomal genetic disease transmitted in an autosomal recessive mode. It is a rare bone disease characterized by osteosclerosis of the skeleton, short stature, bone fragility resulting in spontaneous and repeated fractures, and characteristic facial dysmorphia. Molecular testing remains indispensable for confirming the diagnosis, establishing genotype-phenotype correlations and genetic counseling. Identification of the mutation in the index case will also enable early prenatal diagnosis of these couples, given the high risk of recurrence (25% with each pregnancy) and the risk of delayed psychomotor acquisition (estimated at 30%).Management of pycnodysostosis is symptomatic and multidisciplinary, to limit complications, but also underlining the importance of early diagnosis.