title: Multicentric carpotarsal osteolysis syndrome
text: # 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.
  
  ## 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.
  
  