La maladie des exostoses multiples

Abstract

Hereditary multiple exostosis (HEM) is one of the most common hereditary diseases. It is characterized by the proliferation of bone protuberances, especially located in the metaphysis of long bones. The disease phenotype may also associate abnormalities in the shape and length of long bones, such as the typical “Bessel Hagen” deformity. Clinically, the main complaint of patients remains pain, but the psychological and social consequences should not be minimized. The rare complication (2 to 5% of cases) but the most feared is the transformation into chondrosarcoma, which motivates regular clinical and radiological monitoring of these patients. This follow-up, although essential, remains poorly defined, including at a minimum, an annual clinical examination and radiological follow-up based on the symptoms described by the patients. The treatment remains mainly surgical, with patients being most often multi-operated during the course of the disease. Medical treatment remains secondary. In recent years, progress has been made in understanding the pathophysiology of this disease, particularly with the discovery of the mutation of EXT genes, found in 80% of HME cases. These tumor suppressor genes encode proteins that act in the synthesis of heparan sulfates (HS). The decrease in the amount of HS leads to changes in certain metabolic pathways, which explains the development of ectopic growth plaques, which are the cause of bone exostosis, but also the poor longitudinal growth of long bones. The greater knowledge of the mechanisms underlying this disease makes it possible to consider potential therapeutic targets.