Autosomal dominant osteopetrosis type 1

Autosomal dominant osteopetrosis type 1 (ADO1), also known as autosomal dominant osteosclerosis or Albers-Schönberg disease type 1, is a rare inherited skeletal disorder characterized by increased bone density, particularly affecting the cranial vault. It is caused by gain-of-function mutations in the LRP5 gene, which encodes a co-receptor in the Wnt signaling pathway that plays a critical role in bone formation. Unlike other forms of osteopetrosis, ADO1 is generally considered a benign condition and is often discovered incidentally on radiographic imaging. The hallmark of ADO1 is generalized osteosclerosis — an increase in bone density throughout the skeleton — with a particular predilection for the skull. Patients typically have thickened cortical bone and increased bone mineral density. Importantly, ADO1 is usually not associated with the fractures, bone marrow failure, or cranial nerve compression that characterize other forms of osteopetrosis. Most affected individuals are asymptomatic or have only mild clinical manifestations. The condition is sometimes associated with a torus palatinus (a bony growth on the palate) and an increased resistance to fractures rather than bone fragility. There is no specific treatment required for most patients with ADO1, as the condition is generally benign. Management is primarily focused on monitoring and supportive care if any complications arise. Genetic counseling is recommended for affected families, as each child of an affected individual has a 50% chance of inheriting the condition. ADO1 should be distinguished from autosomal dominant osteopetrosis type 2 (ADO2, also called Albers-Schönberg disease), which is caused by CLCN7 mutations and is associated with a more significant clinical burden including fractures, osteomyelitis, and cranial nerve palsies.

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