Pycnodysostosis Revealed by Recurrent Fractures: Report of Two Cases.

Pycnodysostosis is a rare autosomal recessive skeletal dysplasia caused by cathepsin K deficiency and characterized by osteosclerosis and bone fragility. Recurrent low-trauma fractures and delayed healing represent major orthopedic challenges, particularly when medullary canal narrowing limits surgical options. We report the case of two brothers born to consanguineous parents who presented with short stature, characteristic craniofacial dysmorphism, acro-osteolysis, and recurrent fractures after minor trauma. The older sibling had the more severe skeletal phenotype, with 14 fractures involving both tibiae, the right femur, and right metatarsals. Most fractures were initially managed conservatively, but later injuries required plate-and-screw fixation because intramedullary nailing was not feasible due to marked bone sclerosis and near obliteration of the medullary canal. The younger sibling showed a milder course, with four tibial fractures treated orthopedically. Radiographs in both patients demonstrated diffuse osteosclerosis, persistent patency of cranial sutures, Wormian bones, mandibular hypoplasia, and distal acro-osteolysis, while calcium-phosphate parameters remained within normal limits. The diagnosis of pycnodysostosis was established on clinicoradiologic grounds. These sibling cases highlight the marked intrafamilial variability of pycnodysostosis and the technical difficulties of fracture management in sclerotic bone. Early recognition of the characteristic phenotype is essential to avoid misdiagnosis and to guide long-term multidisciplinary follow-up with individualized orthopedic planning.