Written by Madelaine Pister
Fibrodysplasia Ossificans Progressiva, also known as Münchmeyer disease is an extremely rare connective tissue disease to which there are currently no known cures or treatments. This is a condition that stems from a genetic mutation in the ACVR1 gene, subsequently wreaking havoc on the body’s repair systems. Likewise, when an area of fibrous tissue within the body experiences trauma or is in need of repair, this mutation promotes the formation of bone as healing for the affected area. Construction known as ossification takes place, where the body begins to lay down new bone material using cells called osteoblasts rather than going through the normalized healing process. Where this formation is normally caused by injury, it is also known to be a spontaneous process. Slowly, an individual’s muscles, tendons, ligaments and other soft tissues begin to solidify and eventually form a secondary skeleton which prevents most of a patient’s free movement.
In many cases, tell-tale signs of the disease can be identified during a patient’s younger years. At birth, those afflicted with Münchmeyer disease often present with malformed big toes, as well as the possibility of missing major joints, or the presence of a lump on a minor ligament. While these symptoms are quite indicative of this disease, due to the rarity of the diagnosis they are often overlooked. Instead, it is noted that most initial flare-ups of the ailment appear before the age of 10, and is, therefore, better diagnosed after some progression. Flare-ups are commonly identified through the arrival of tumour-like lumps which form on the skin suddenly. Conventionally, just as natural bone does, the unwanted bone growth progresses downwards: beginning at the neck, then at the shoulders, arms, and chest region, then at the feet. However, as noted before, the formation of bone is also brought on by injury, therefore “out of character” growth is usually spotted in other places of the body.
Münchmeyer disease is an autosomal dominant disorder, meaning that the dominant allele of its gene is affected increasing the likeliness of an affected parent’s offspring to obtain the disease. Essentially, the protein which aids in ossification (bone growth) is inhibited once a fetuses’ bones are formed, although, those with Münchmeyer never have this protein deactivated. As a result, when connective or muscle tissue experiences injury or growth, the cells incorrectly express the active gene for an enzyme that regulates bone repair (often seen during apoptosis/regulated cell death). Consequently, the bone that results forms its own skeletal system over time, which often takes the opportunity to fuse with many parts of the natural skeleton. As this disease progresses the individual slowly lose all movement, whilst their cardiac, smooth muscles, and extraocular muscles remain unharmed in a “stone” body.
Whilst there is no cure, many routes have been tested in hope for one. Most notably, attempted surgical removal of unwanted bones have been performed, however, the patients were sadly met with explosive bone growth during the recovery process. Again, revealing the importance genetics plays in this disease’s arrival and function overall as the physiological removal provided no healing.
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