Clinical and genetic characterization of three Russian patients with pycnodysostosis due to pathogenic variants in the CTSK gene.

Background: Pycnodysostosis (PD, OMIM # 265800) is a rare variant of skeletal dysplasia with an autosomal recessive type of inheritance, characterized by a combination of specific features such as disproportionate nanism, generalized osteosclerosis, and distinct craniofacial dysmorphism. Radiographic features include acro-osteolysis of the distal phalanges in association with sclerosing bone lesions with multiple fractures. The polymorphism of the clinical manifestations of pycnodysostosis and low prevalence of the disorder lead to the difficulties with early.