Polycystic bone disease: A new family.

Bone cysts are benign fluid-filled lytic lesions, which can be unicameral (UBC) or partially separated. Usually, they are solitary and resolve spontaneously. Even if they are often asymptomatic, pathological fractures can occur. Multiple UBC are very rare and, to the best of our knowledge, only one familial case of multiple bone cysts has been reported to date; this condition was named Polycystic Bone Disease (PCBD). Here, we report three further related patients affected by PCBD, thus providing new insights into the clinical and radiological characterization of this ultra-rare disease. Furthermore, we describe for the first time the pathological phenotype of this condition. Our study confirms that PCBD represents a specific autosomal dominant condition, which should be included in the nosology of skeletal disorders. We hope that the report of further cases will allow the characterization of the molecular basis of this condition.