Refsum Disease: Causes, Symptoms, Diagnosis, and Treatment
Refsum is a rare genetic disorder caused by lipid metabolism errors. It is distinguished by the growth of plasma and tissue in blood. The lipid metabolism errors affect a process which prevents myelin sheath from developing or working correctly. Myelin sheath is an isolated membrane made up of the nerve cell fats and proteins.
Dr. Sigwald Refsum identified Refsum disease in 1946 for the first time; it is also known as adult Refsum disease or classic Refsum disease. Refsum in adults differ from Refsum, a child disease caused by cell sub-compartmental defects known as peroxisomes. Males and females are equally affected.
What Are The Symptoms Of Refsum Diseases?
Peripheral neuropathy, Credits: canva
The type and symptoms of Refsum disease vary from one person to another. The seriousness of the condition depends on the phytanic acid levels in the body. The following are typical signs and symptoms.
During birth, individuals with Refsum disease may appear normal. Some people may have shorter bones in their hands and feet.
During the age of 10 to 20 years, individuals may have a loss of night vision which is the first symptom. The loss of night vision is due to the deterioration of light-sensing cells in the retina. The loss of peripheral vision and full blindness may happen over years.
Other problems with the eye include abnormally little pupils, cloudiness in eyes, and quick unintentional eye movement.
Other symptoms include loss of sense of smell and taste, peripheral neuropathy, rough, scaly patches of the skin, and general weakness.
Some people may not develop any symptoms till 50 years of age.
What Are The Causes Of Refsum Diseases?
In 90% of the cases, Refsum disease is due to a mutation in the PHYH gene (in chromosome 10). The gene code of PHYH for the Phytanoyl-CoA enzyme is used to break down phytanic acid in the peroxisome. The typical presence of phytanic acid is dairy, beef, lamb and other feed originating from ruminant animals as well as certain sea foods. Due to the improper functioning of peroxisomes, phytanic acid accumulates in the cells.
In some cases, a mutation in the PEX7 gene (chromosome 6) is also seen. These gene mutations cause peroxisome abnormality.
Is Refsum Disease Common?
Refsum disease occurs in 1 in 1,000, 000 people. The risk of the disease increases if there is a history of consanguineous marriage in the family. Refsum disease is an autosomal recessive disease.
How Refsum Disease Is Diagnosed?
Gene mutations, Credits: canva
High levels of phytanic acid (10 to 100 fold higher) are identified in the blood. Also, the levels of pristanic acid are usually low. A molecular genetic examination to identify mutations in either PHYH or PEX7 genes confirms the diagnosis. An enzyme analysis is also conducted in skin biopsy to assess the function of Phytanoyl-CoA hydroxylase.
How Is Refsum Disease Treated?
Beef, Credits: canva
An person with Refsum must reduce beef, lamb, some sea products and dairy products. Which tends to restrict the entry of phytanic acid from fat or liver into the blood. Dietary limitation on phytanic acid consumption contributes to ichthyosis, sensory neuropathy, and ataxia reduction or resolve. Also, a low phytanic acid diet may slow the progression of vision and hearing loss.
If the levels of phytanic acid are very high, removal or reinfusion of blood may be necessary.
Also, patients with Refsum disease need to avoid fasting and rapid weight loss as it may release phytanic acid stored in the body.
A professional nutritionist and physician can assist patients in understanding the possibility of acute phytanic acid and can help patients maintain a low diet of phytanic acid. For affected persons and their families, genetic counseling is recommended.