A Review of the Clinical, Radiological and Biochemical Characteristics and Genetic Causes of High Bone Mass Disorders.

BACKGROUND: High bone mass (HBM) disorders are a group of clinically and genetically heterogeneous bone diseases characterized by increased bone density on radiographs, due to progressive bone overgrowth or impaired bone resorption, or both. Some HBM cases are secondary to other diseases, such as chronic hepatitis C virus infection. Despite the great advance in gene diagnostic technology, the majority of HBM individuals remain undiagnosed.

OBJECTIVE: In this review, we will summarize the clinical, radiological and biochemical characteristics of HBM cases due to varying etiologies, since these features are helpful in the differential diagnosis of HBM.

RESULTS: Each subgroup of HBM cases shows distinctive clinical, radiological and biochemical characteristics. HBM, due to bone overgrowth, was designated as sclerosteosis, as a result of mutations located in genes critically involved in the Wnt/beta-catenin signal pathway. Mutations in genes encoding factors relevant to the differentiation and maturation of osteoclasts, or critical for the acidification and resorption of osteoclasts may lead to osteopetrosis. Hepatitis C associated osteosclerosis is characterized by a generalized increase in bone mass and markedly elevated serum levels of bone specific alkaline phosphatase.

CONCLUSION: The clarification of the etiologies of HBM may have a breakthrough role in understanding the molecular mechanisms involved in bone metabolism and may provide new pathways for the intervention of osteoporosis.