In Metachondromatosis, enchondromas involves the iliac crests and metaphyses of long bones, often the proximal femur.

Usually, these tumors are painless; however, when present in the hands or feet, or in multiple lesions, as typically seen, bone deformity can occur.

[9] Metachondromatosis is inherited in an autosomal dominant manner, needing only one copy of the defective gene to cause the disorder.

[2] SHP-2 plays an important role in regulating expression of the Indian Hedgehog gene (IHH),[11] which is associated with differentiation in chondrocytes (specialized cells in cartilage tissue).

[7] Individuals affected by metachondromatosis generally demonstrate high levels of IHH expression, which is believed to be responsible for the tumor growth.

[11] Given that the mutation causes a loss of protein function and displays a dominant inheritance pattern, it is hypothesized that individuals homozygous for the disorder would display greater symptoms than heterozygous individuals, though insufficient data is available to evaluate these claims due to the rarity of the disease.

[11] Conversely, some heterozygous individuals have shown minimal effects, leading to the disorder’s designation as incompletely penetrant.

[12] Using radiographic methods, osteochondromas can be seen at the metaphyses of the short tubular bones, such as those in the hands and feet, pointing towards the joints.

This is a condition in which the long bones are primarily affected, and the lesions point away from the joint or growth plate.