Multicentric osteolysis, nodulosis, and arthropathy (MONA) is a chronic skeleton syndrome, characterized by facial dysmorphism, subcutaneous fibrocollagenous nodules, carpal and tarsal osteolysis and interphalangeal joint erosions. Other features can include coarse face, corneal opacities, hypertrichosis and gum hypertrophy. Some patients also have skin abnormalities including patches of dark, thick, and leathery skin. The disease follows a recessive pattern of transmission.
Mutations in the MMP2 gene are the cause of multicentric osteolysis, nodulosis, and arthropathy. This gene gives instructions for making an enzyme called matrix metallopeptidase 2, which catalyses the type IV collagen. These mutations cause reduction in the activity of the matrix metallopeptidase 2 enzyme. Yet, it is unclear how a loss of enzyme activity leads to the specific features of MONA.