Multicentric Carpotarsal Osteolysis: a Contemporary Perspective on the Unique Skeletal Phenotype

Area of Science:

• Genetics
• Molecular Biology
• Orthopedics

Background:

• Multicentric carpotarsal osteolysis (MCTO) is an ultra-rare skeletal disorder.
• Characterized by osteolysis of carpal and tarsal bones, craniofacial deformities, and nephropathy.
• The underlying molecular mechanisms remain poorly understood.

Purpose of the Study:

• To review current perspectives on MafB protein function in MCTO pathogenesis.
• To explore the roles of inflammation and bone formation in the skeletal phenotype.
• To identify areas for future research toward developing rational therapies for MCTO.

Main Methods:

• Literature review of recent findings on MCTO and MAFB gene mutations.
• Analysis of the presumed gain-of-function mechanism of MAFB mutations.
• Appraisal of current understanding of osteolysis, inflammation, and bone formation in MCTO.

Main Results:

• MCTO is linked to heterozygous mutations in the MAFB gene, encoding the transcription factor MafB.
• Mutations lead to amino acid changes in a critical phosphorylation region, suggesting a gain-of-function.
• Fewer than 60 MCTO patients have been described, with a lack of clear genotype-phenotype correlation.

Conclusions:

• Osteolysis due to excessive osteoclast activity is considered primary, but anti-resorptive agents show limited efficacy.
• Further research is crucial to elucidate the complex pathogenesis of MCTO.
• Understanding MafB protein action, inflammation, and bone formation is key to developing effective treatments.