Refsum Disease Health Article

Diagnosis

Refsum disease is diagnosed though a combination of consistent medical history, physical exam findings, and laboratory and genetic testing. When patients with Refsum disease present to their physicians complaining of visual problems or muscle weakness, physical signs of retinitis pigmentosa, peripheral neuropathy, cerebellar ataxia, or skin and bone changes (as discussed above) are often noted. These findings raise suspicion for a genetic syndrome or metabolic disorder, and further tests are conducted.

Laboratory tests reveal several abnormalities. Normally, phytanic acid levels are essentially undetectable in the plasma. Thus, the presence of high levels of phytanic acid in the bloodstream is highly indicative of Refsum disease. If necessary, a small portion of the patient's connective tissue can be sampled and grown in a laboratory and tested to demonstrate a failure to process phytanic acid appropriately. Other associated laboratory abnormalities include the presence of high amounts of protein in the fluid that bathes the spinal cord, or abnormal electrical responses recorded from the brain, muscles, heart, ears, retina, and various nerves as a result of nervous system damage.

Genetic testing can also be performed. When a diagnosis of Refsum disease is made in a child, genetic testing of the PAHX/PHYH gene can be offered to determine if a specific gene change can be identified. If a specific change is identified, carrier testing can be offered to relatives. In families where the parents have been identified to be carriers of the abnormal gene, diagnosis of Refsum disease before birth is possible. Prenatal diagnosis is performed on cells obtained by amniocentesis (withdrawal of the fluid surrounding a fetus in the womb using a needle) at about 16–18 weeks of pregnancy or from the chorionic villi (a part of the placenta) at 10–12 weeks of pregnancy.

Treatment and management

There is no cure for Refsum disease, thus treatment focuses on reducing levels of phytanic acid in the bloodstream to prevent the progression of tissue damage. Phytanic acid is not made in the human body and comes exclusively from the diet. Restriction of phytanic acid-containing foods can slow progress of the disease or reverse some of the symptoms. Patients are advised to maintain consumption of phytanic acid below 10 mg/day (the normal intake is approximately 100 mg/day). Sources of high levels of phytanic acid to be avoided include meats (beef, lamb, goat), dairy products (cream, milk, butter, cheese), and some fish (tuna, cod, haddock). Plasma levels of phytanic acid can be monitored periodically by a physician to investigate the effectiveness of the restricted diet and determine if changes are required. As a result of dietary restriction, nutritional deficiencies may result. Consultation with a nutritionist is recommended to assure proper amounts of calories, protein, and vitamins are obtained through the diet, and nutritional supplements may be required.

Because phytanic acid is stored in fat deposits within the body, it is important for patients with Refsum disease to have regular eating patterns; with even brief periods of fasting, fat stores are converted to energy, resulting in the release of stored phytanic acid into the blood stream. Thus, unless a patient assumes a regular eating pattern, repeated and periodic liberation of phytanic acid stores results in greater tissue damage and symptom development. For these same reasons, intentional weight loss though calorie-restricted diets or vigorous exercise is discouraged.

Another useful adjunct to dietary treatment is plasmapheresis. Plasmapheresis is a procedure by which determined amounts of plasma (the fluid component of blood that contains phytanic acid) is removed from the blood and replaced with fluids or plasma that do not contain phytanic acid. Regular utilization of this technique allows people who fail to follow a restricted diet to maintain lower phytanic acid levels and experience less tissue damage and symptoms.

Patients with Refsum disease should be seen regularly by a multidisciplinary team of health care providers, including a pediatrician, neurologist, ophthalmologist, cardiologist, medical geneticist specializing in metabolic disease, nutritionist, and physical/occupational therapist. People with Refsum disease, or those who are carriers of the abnormal gene or who have an relative with the disorder, can be referred for genetic counseling to assist in making reproductive decisions.

Prognosis

The prognosis of Refsum disease varies dramatically. The disorder is slowly progressive and, if left untreated, severe symptoms will develop with considerably shortened life expectancy. However, if diagnosed early, strict adherence to a phytanic acid-free dietary regimen can prevent progression of the disease and reverse skin disease and some of the symptoms of peripheral neuropathy. Unfortunately, treatment cannot undo existing damage to vision and hearing.

BOOKS

"Peroxisomal Disorders." In Nelson Textbook of Pediatrics. Edited by R. E. Behrman. Philadelphia: W.B. Saunders, 2000, pp 318-384.

PERIODICALS

Weinstein, R. "Phytanic acid storage disease (Refsum's disease): Clinical characteristics, pathophysiology and the role of therapeutic apheresis in its management." Journal of Clinical Apheresis 14 (1999): 181-184.