Inherited osteolysis (also known as vanishing bone syndrome) is characterized by abnormal destruction and resorption of bone. In the July issue of Nature Genetics, Martignetti et al. identify mutations in the matrix metalloproteinase 2 gene (MMP2) in several Saudi Arabian families with osteolysis (Nature Genetics 2001, 28:261-265). They performed a genome-wide search for homozygous-by-descent microsatellite markers, in order to hone in on a region of chromosome 16q12 that includes the MMP2 gene. MMP2 enzymatic activity could not be detected in serum or cultured skin fibroblasts from these patients. Martignetti et al. identified two homoallelic MMP2 mutations: a missense mutation (R101H) within the prodomain and a non-sense mutation (Y244X) that deletes the catalytic sites. The authors suggest that the unexpected role of MMP2 in osteolysis may involve deregulated extracelluar matrix breakdown leading to an imbalance between bone synthesis and resorption.