What is Refsum disease?
Refsum disease is a rare, inherited condition caused by an error of lipid metabolism. It is characterized by the loss of vision and smell, among other symptoms. Doctors are unsure of this disease’s prevalence, although they are aware that it is rare.
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What are the symptoms of Refsum disease?
A major symptom of Refsum disease is retinitis pigmentosa, which causes vision to deteriorate as cells in the retina die. Affected individuals will also lose their sense of smell, referred to as anosmia.
Less common symptoms include bone abnormalities in the hands and feet, the progressive wasting and weakness of muscles, issues with coordination and balance, dry and scaly skin, nerve pain and numbness, hearing loss, and issues with the heart like arrhythmia.
What causes Refsum disease?
A mutation in the PHYH gene causes 90% of cases of Refsum disease, with the remaining 10% resulting from a mutation in the PEX7 gene. Both of these genes play a role in the breakdown of phytanic acid, a form of fatty acid. Peroxisomes are structures that hold enzymes necessary for the breakdown. The mutations cause an issue with the peroxisomes, resulting in the common symptoms.
These genes are inherited in an autosomal recessive pattern, meaning both parents must pass down the affected gene in order for a child to have the symptoms.
How is Refsum disease diagnosed?
Doctors will take either a blood or urine sample and test it for phytanic acid. If it is present, then one will be diagnosed with Refsum disease.
What are the treatments for Refsum disease?
As phytanic acid is found in many foods, treatment consists of a strict diet in which these foods are avoided. This diet restricts beef, lamb, dairy products, and some seafood. Doctors may also remove and reinfuse blood plasma. If other treatment is required, it is symptomatic and supportive.