Case report: Multicentric carpal/tarsal osteolysis: imaging review and 25-year follow-up

A report of 5 Indian families with multicentric carpotarsal osteolysis syndrome

Multicentric carpotarsal osteolysis syndrome (MCTO) is a rare autosomal dominant skeletal dysplasia characterised by swelling and restriction of movement in the wrist and ankle joints, as well as osteolysis of the carpal and tarsal bones, that can be misdiagnosed as juvenile idiopathic arthritis. We describe five Indian families with heterozygous nonrecurrent missense pathogenic variants in exon 1 of MAF bZIP transcription factor B (MAFB).

Trio Clinical Exome Sequencing in a Patient With Multicentric Carpotarsal Osteolysis Syndrome: First Case Report in the Balkans

Exome sequencing can interrogate thousands of genes simultaneously and it is becoming a first line diagnostic tool in genomic medicine. Herein, we applied trio clinical exome sequencing (CES) in a patient presenting with undiagnosed skeletal disorder, minor facial abnormalities, and kidney hypoplasia; her parents were asymptomatic. Testing the proband and her parents led to the identification of a de novo mutation c.188C>T (p.Pro63Leu) in the MAFB gene, which is known to cause multicentric carpotarsal osteolysis syndrome (MCTO). The c.188C>T mutation lies in a hotspot amino acid stretch within the transactivation domain of MAFB, which is a negative regulator of RANKL-induced osteoclastogenesis. MCTO is an extremely rare autosomal dominant (AD) disorder that typically arises spontaneously and causes carpotarsal osteolysis, often followed by nephropathy. To the best of our knowledge, this is the first study reporting genetically diagnosed MCTO in the Balkans.

Multicentric carpotarsal osteolysis is caused by mutations clustering in the amino-terminal transcriptional activation domain of MAFB

Multicentric carpotarsal osteolysis (MCTO) is a rare skeletal dysplasia characterized by aggressive osteolysis, particularly affecting the carpal and tarsal bones, and is frequently associated with progressive renal failure. Using exome capture and next-generation sequencing in five unrelated simplex cases of MCTO, we identified previously unreported missense mutations clustering within a 51 base pair region of the single exon of MAFB, validated by Sanger sequencing. A further six unrelated simplex cases with MCTO were also heterozygous for previously unreported mutations within this same region, as were affected members of two families with autosomal-dominant MCTO. MAFB encodes a transcription factor that negatively regulates RANKL-induced osteoclastogenesis and is essential for normal renal development. Identification of this gene paves the way for development of novel therapeutic approaches for this crippling disease and provides insight into normal bone and kidney development.

Carpal-tarsal osteolysis with elbow involvement

Carpal-tarsal osteolysis is a rare condition that manifests as the progressive resorption of carpal and tarsal bones in young children. The diagnosis of this condition is often difficult and delayed as the initial clinical presentation is non-specific. Radiographic changes occur gradually, are often not seen at presentation and depend on recognising loss of bone in the ossification centres of the carpus and tarsus. MRI demonstrates morphological abnormalities in the cartilaginous, as well as the osseous components, of the developing carpal and tarsal bones and therefore may be helpful in predating the radiographic changes. Ultrasound appears to contribute little to the diagnosis and may be misleading. Exclusion of other conditions, particularly juvenile idiopathic arthritis, is important in making the diagnosis. MRI can be useful in excluding an inflammatory arthropathy, and suggesting the diagnosis of carpal-tarsal osteolysis.