Hereditary Multiple Osteochondroma with Incomplete Penetrance in a Lebanese Family: A Case Report

Background: Hereditary multiple osteochondroma (HMO) is a rare autosomal dominant disease with high penetrance reaching 95 to 100%. It manifests during childhood in most of the times. The spectrum of the disease is wide. It is classified into 2 types depending on the number of cases and the penetrance in the same generation. The most feared complication of this disease is the malignant transformation. Establishing a screening protocol requires the identification of the true prevalence and penetrance of the disease. Case Report: A 17-year-old girl presented with multiple painful lesions in the lower extremities. Physical examination of the patient and her siblings allowed the diagnosis of HMO with incomplete penetrance, and the construction of a pedigree of the family. Surgical treatment was sufficient to control the patient’s symptoms. Conclusion: Being the first case in Lebanon, this report adds more awareness about this rare disease. By increasing awareness, this report can have an impact on the transmission and the number of affected cases in the country. Furthermore, these data, when added to the available evidence worldwide, can be used in the determination of true penetrance of the disease, and the creation of accurate classification and screening protocol.