Fibrodysplasia ossificans progressiva: molecular genetic causes, clinical and morphological characteristics, and therapeutic approaches to treatment

Fibrodysplasia ossificans progressiva (FOP) is an extremely rare genetic disorder with a prevalence of approximately 1 case per 1.5–2.0 million individuals. The primary cause of the disease lies in mutations of the ACVR1 gene, which encodes the homonymous receptor involved in the regulation of bone histogenesis. The most common genetic variant is the 617GA single nucleotide substitution (R206H, rs121912678), resulting in the replacement of arginine with histidine. This variant is observed in over 95% of all registered patients with fibrodysplasia ossificans progressiva. The mutation disrupts intracellular signaling, leading to the formation of abnormal heterotopic bone tissue in muscles, tendons, and ligaments. The clinical presentation may vary: some patients experience additional symptoms presumably associated with rare mutations in other domains of the ACVR1 receptor. Despite active research, the exact precursor cells responsible for pathological osteogenesis remain unidentified. Scientists hypothesize the involvement of multiple cell types, including mesenchymal stem cells and endothelial cells. Currently, no effective treatment exists for fibrodysplasia ossificans progressiva, underscoring the urgent need for novel therapeutic targets. Gene therapy, successfully employed in other monogenic disorders, represents a promising direction. Several experimental approaches, including targeted inhibitors of the ACVR1 signaling pathway, are undergoing preclinical and clinical trials.