Monarch Disease Ontology term MONDO_0009816 (autosomal recessive osteopetrosis 2) is any autosomal recessive malignant osteopetrosis in which the cause of the disease is a mutation in the TNFSF11 gene. Also known as: OPTB2, TNFSF11 autosomal recessive malignant osteopetrosis, TNFSF11 autosomal recessive osteopetrosis, TNFSF11-related osteopetrosis, autosomal recessive malignant osteopetrosis caused by mutation in TNFSF11, autosomal recessive osteopetrosis caused by mutation in TNFSF11, autosomal recessive osteopetrosis type 2, mild autosomal recessive form osteopetrosis.