multicentric carpotarsal osteolysis syndrome multicentric carpotarsal osteolysis syndrome multicentric carpotarsal osteolysis syndrome (mcto) is a rare autosomal dominant condition. this condition is also known as idiopathic multicentric osteolysis with nephropathy. it is characterised by carpal-tarsal destruction and kidney failure. multicentric carpotarsal osteolysis syndromeother namesmctothis condition is inherited in an autosomal dominant manner.specialtymedical genetics signs and symptoms the presentation is of gradual loss of the small bones in the carpus and tarsus. this may lead to joint subluxation and instability. the kidney failure, when present, usually presents as the presence of protein in the urine. in some cases, there may also be craniofacial abnormalities including triangular facies micrognathia maxillary hypoplasia exophthalmos histology of renal biopsies show glomerulosclerosis and severe tubulointerstitial fibrosis. intellectual disability may occur. genetics this condition is caused by mutations in the transcription factor mafb, or v-maf musculoaponeurotic fibrosarcoma oncogene homolog b (mafb), gene. this gene encodes a basic leucine zipper (bzip) transcription factor. the gene is located on the long arm of chromosome 20 (20q11.2-q13.1). pathogenesis how this mutation causes the clinical picture is not currently clear. diagnosis the diagnosis may be suspected on the basis of the constellation of clinical features. it is made by sequencing the mafb gene. classification this condition has been classified into five types. type 1: hereditary multicentric osteolysis with dominant transmission type 2: hereditary multicentric osteolysis with recessive transmission type 3: nonhereditary multicentric osteolysis with nephropathy type 4: gorham–stout syndrome differential diagnosis the condition should be differentially diagnosed from juvenile rheumatoid arthritis and other genetic skeletal dysplasias as multicentric osteolysis, nodulosis, and arthropathy. treatment optimal treatment for this condition is unclear. bisphosphonates and denosumab may be of use for the bone lesions. cyclosporine a may be of use for treating the nephropathy. steroids and other immunosuppressant drugs do not seem to be of help. history this condition was first described by shurtleff et al. in 1964.