A rare genetic mutation turns muscle and connective tissue into solid bone
In short: Imagine your body treating every bump or bruise as a signal to build more bone. In patients with Fibrodysplasia Ossificans Progressiva, a genetic error causes muscles, tendons, and ligaments to gradually transform into a second skeleton, eventually locking joints and limiting movement entirely.
Fibrodysplasia ossificans progressiva (FOP) is a rare genetic condition characterized by heterotopic ossification—the gradual replacement of muscles, tendons, and ligaments with new bone. This transformation often begins in early childhood, typically manifesting around the neck, shoulders, and back. These developments are frequently triggered by flare-ups, which are the body's reaction to trauma such as an injury, surgery, or even a viral illness like the flu.
The biological mechanism is driven by a mutation in the ACVR1 gene. This gene provides instructions for creating type 1 receptors for bone morphogenic protein (BMP) within muscles and cartilage. In a healthy body, these receptors regulate how bones and muscles develop. However, in those with FOP, the mutated receptor acts like a light switch that is stuck in the 'on' position, failing to stop the production of proteins even when it should.
Diagnosis often begins at birth through a specific physical marker: a malformed, short big toe that may point at an odd angle or grow over the second toe. Nearly 50% of cases also involve similar malformations of the thumbs. Because FOP is an autosomal dominant condition, a child has a 50% chance of inheriting it if a parent carries the gene. However, many cases arise from a new, random mutation known as a de novo mutation, meaning there may be no family history of the disorder.
As the condition progresses, the buildup of bone can lead to permanent immobility, joint stiffness, and locked joints. Patients may also experience difficulty eating or speaking, hearing impairment, and skeletal issues like scoliosis or kyphosis. While the speed of bone development varies by individual, the physical impact remains profound, often resulting in a permanent loss of mobility.
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Sources
- Summary by Intellect · source: The People Who Slowly Turn to Bone
- Also: Fibrodysplasia Ossificans Progressiva: Causes, Symptoms, Treatment, Outlook
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