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
ExophthalmosHistology 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.
Allopurinol was marketed at the time by Burroughs Wellcome. Allopurinol is a generic drug sold under a variety of brand names, including Allohexal, Allosig, Milurit, Alloril, Progout, Ürikoliz, Zyloprim, Zyloric, Zyrik, and Aluron. See also
Lesinurad/allopurinol, a fixed-dose combination drug
Hydroxychavicol, potent xanthine oxidase inhibitor

References
Further reading
Dean L (March 2016). "Allopurinol Therapy and HLA-B*58:01 Genotype". In Pratt VM, McLeod HL, Rubinstein WS,  et al. (eds.). Medical Genetics Summaries. National Center for Biotechnology Information (NCBI). PMID 28520356. External links
"Allopurinol". Drug Information Portal. U.S. National Library of Medicine. "PRODUCT INFORMATION Allopurinol Tablets USP". U.S. National Library of Medicine. Medication handout sheet (Revised: 07/2019 0603–2115)
Allopurinol pathway on PharmGKB