Amyotrophy is a weakness and wasting of muscles or limbs. There are many different conditions that are related to amyotrophy, but the most common two are monomelic amyotrophy (MMA) and hereditary neuralgic amyotrophy (HNA). These two conditions are similar in that they include the wasting away of a muscle or limb, but HNA is usually concentrated at the shoulder and accompanied by severe pain. MMA also usually occurs in the upper limbs, but can also occur in the legs and isn’t accompanied by pain.
MMA has no clearly defined cause. The condition usually presents in a part of one of the patient’s upper limbs. The muscle will waste away, but this will happen gradually before reaching a period of stasis, where the condition does not get noticeably worse. There is a chance that the condition will spread to the limb on the other side of the body, but this does not usually happen. MMA is most common in Asia, particularly in Japan and India. The condition typically affects males, and is more likely to occur between the ages of 15 and 25.
The second disease, HNA, is known to be a hereditary condition, meaning that it is only likely to occur if the patient has a family history of it. The SEPT9 gene is known to be associated with the development of HNA, in around 85 percent of reported cases. If one of the patient’s parents has the condition, he will have a 50 percent chance of developing the condition himself. HNA first manifests through extreme pain in the shoulder or upper arm, and after a couple of weeks, amyotrophy will develop in the affected limb. The condition usually develops around the age of 28, and the patient will experience attacks of pain in the affected limb. These attacks will become less frequent as the patient’s age increases.
Both MMA and HNA are conditions for which there is no cure, and treatment is usually geared toward making the patient’s life more manageable. With HNA, because of the severe pain usually associated with the condition, the main goal of treatment is pain management. MMA treatment is more focused on strengthening the weak limb. Prevention is difficult in both conditions, although prenatal diagnosis of HNA is a possibility. This test is available for any parents who have a risk of transmitting the mutated gene to their child.