Refsum Disease
Description
Refsum disease, also known as phytanic acid storage disease, is a rare inherited disorder that primarily affects the nervous system. This condition disrupts the body‘s ability to break down a fatty acid called phytanic acid, leading to its accumulation in various tissues, including the brain, nerves, and liver. This buildup can cause a range of neurological problems, potentially impacting vision, hearing, balance, and motor function. Refsum disease is a lifelong condition, but with proper management, individuals can live fulfilling lives.
Genes Involved
Refsum disease is caused by mutations in the PHYH gene. This gene provides instructions for making an enzyme called phytanoyl-CoA hydroxylase. This enzyme is essential for breaking down phytanic acid, a fatty acid found in animal products like dairy, meat, and fish. When the PHYH gene is mutated, the body cannot effectively break down phytanic acid, leading to its accumulation and the development of Refsum disease.
Recognizing the Signs and Symptoms
Recognizing the signs and symptoms of Refsum disease is crucial for timely diagnosis and intervention. Symptoms can vary in severity and often manifest in childhood or early adulthood. Some common signs and symptoms include:
- Vision problems: Night blindness is often an early symptom, progressing to more significant visual impairments like retinitis pigmentosa.
- Hearing loss: Sensorineural hearing loss can occur, affecting the ability to hear high-frequency sounds.
- Balance issues: Ataxia, characterized by difficulty with coordination and balance, can lead to unsteady gait and falls.
- Nerve damage: Peripheral neuropathy, affecting the nerves in the arms and legs, may cause numbness, tingling, and weakness.
- Skin problems: Scaly skin, ichthyosis, can occur, particularly on the limbs and trunk.
- Liver and kidney problems: Refsum disease can affect liver and kidney function, leading to elevated enzyme levels and potential complications.
- Delayed development: In some cases, children with Refsum disease may experience delays in motor skills or cognitive development.
Causes
Refsum disease is caused by genetic mutations in the PHYH gene. These mutations are inherited from parents and disrupt the production of a crucial enzyme responsible for breaking down phytanic acid, a fatty acid found in certain foods. This inherited deficiency leads to the buildup of phytanic acid in the body, ultimately causing the symptoms of Refsum disease.
Inheritance/recurrence risk
Refsum disease follows an autosomal recessive inheritance pattern. This means that an individual needs to inherit two copies of the mutated PHYH gene, one from each parent, to develop the condition. If both parents are carriers of the mutated gene, each child has a 25% chance of inheriting the condition, a 50% chance of being a carrier, and a 25% chance of inheriting two normal copies of the gene. Individuals with Refsum disease are not typically carriers of the mutation.
