Fibrodysplasia Ossificans Progressiva Mimics Generalized Dystonia Disorder: A Case Report

Fibrodysplasia ossificans progressiva (FOP) is an autosomal dominant disorder characterized by congenital deformities of the big toes and the progressive formation of extra-skeletal bone within soft tissues. The underlying genetic cause of FOP is mostly due to gain-of-function mutations in the AVCR1/ALK2 genes. These mutations cause aberrant bone morphogenetic protein (BMP) signaling pathways and eventually result in cumulative musculoskeletal impairment. FOP has a prevalence of approximately one in every 2 million people worldwide, with nearly 90% of patients being misdiagnosed, possibly leading to an underestimation of its true prevalence. To the best of our knowledge, there are only three reported cases in Saudi Arabia. We report a case of a 21-year-old female patient, a product of a consanguineous marriage, referred to the neurology clinic for new-onset dysphagia and dysarthria in association with progressive painful muscle stiffness, which started at the age of four years. The diagnosis of generalized dystonia disorder was suspected, but eventually the whole exome sequencing showed a pathogenic missense mutation in the ACVR1 gene, confirming the diagnosis of FOP. FOP is a rare, debilitating disorder that can be difficult to diagnose and manage. Current research efforts are focused on early diagnosis and a high index of suspicion to help prevent unnecessary investigations and procedures, slow the progression of the disease, and promote patients' quality of life and long-term outcomes.