Erythromelalgia
Erythromelalgia is a painful peripheral neuropathy characterized by episodes of severe burning pain, redness, and swelling in the extremities, typically triggered by increases in body temperature.
Overview
Erythromelalgia is a condition characterized by episodes of pain, redness, and swelling in various parts of the body, particularly the hands and feet. It is often considered a form of peripheral neuropathy because it affects the peripheral nervous system, which connects the brain and spinal cord to muscles and to cells that detect sensations such as touch, smell, and pain.
The signs and symptoms of erythromelalgia typically begin in childhood, although mildly affected individuals may experience their first pain episode later in life. As the disease progresses over time, the hands and feet may become constantly red, and the affected areas can extend from the hands to the arms, shoulders, and face, and from the feet to the entire legs.
Symptoms and Triggers
Pain episodes associated with erythromelalgia can be so debilitating that they impede everyday activities, such as wearing shoes and walking, and can prevent affected individuals from regularly attending school or work. Key aspects of these episodes include:
- Triggers: Increased body temperature caused by exercise or entering a warm room. Other triggers include ingesting alcohol or spicy foods, as well as wearing warm socks, tight shoes, or gloves.
- Affected Areas: Primarily the hands and feet, which can experience severe pain, redness, and swelling.
- Progression: Affected areas can expand to include the arms, shoulders, face, and the entirety of the legs.
Frequency
The prevalence of erythromelalgia is unknown.
Causes
An estimated 15 percent of erythromelalgia cases are caused by mutations in the SCN9A gene. This gene provides instructions for making the alpha subunit of a sodium channel called NaV1.7. Sodium channels transport positively charged sodium atoms (sodium ions) into cells and play a key role in generating and transmitting electrical signals. NaV1.7 sodium channels are specifically found in nerve cells called nociceptors, which transmit pain signals to the spinal cord and brain.
Mutations in the SCN9A gene result in NaV1.7 sodium channels that open more easily and stay open longer than normal. This increases the flow of sodium ions into nociceptors, enhancing the transmission of pain signals and leading to the characteristic symptoms of erythromelalgia. It is currently unknown why these pain episodes mainly affect the hands and feet.
Cases of erythromelalgia not caused by SCN9A mutations are thought to have a nongenetic cause or may be caused by mutations in one or more unidentified genes.
Associated Genes
- SCN9A
Inheritance
Some cases of erythromelalgia occur in an autosomal dominant pattern, meaning one copy of the altered gene in each cell is sufficient to cause the disorder. In some instances, an affected person inherits the mutation from an affected parent. Other cases result from new mutations in the gene and occur in people with no history of the disorder in their family.
Other Names for This Condition
- Erythermalgia
- Familial erythromelalgia
- Primary erythromelalgia