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Reviewed January 2010
What is Refsum disease?
Refsum disease is an inherited condition that causes vision loss, absence of the sense of smell (anosmia), and a variety of other signs and symptoms.
The vision loss associated with Refsum disease is caused by an eye disorder called retinitis pigmentosa. This disorder affects the retina, the light-sensitive layer at the back of the eye. Vision loss occurs as the light-sensing cells of the retina gradually deteriorate. The first sign of retinitis pigmentosa is usually a loss of night vision, which often becomes apparent in childhood. Over a period of years, the disease disrupts side (peripheral) vision and may eventually lead to blindness.
Vision loss and anosmia are seen in almost everyone with Refsum disease, but other signs and symptoms vary. About one-third of affected individuals are born with bone abnormalities of the hands and feet. Features that appear later in life can include progressive muscle weakness and wasting; poor balance and coordination (ataxia); hearing loss; and dry, scaly skin (ichthyosis). Additionally, some people with Refsum disease develop an abnormal heart rhythm (arrhythmia) and related heart problems that can be life-threatening.
Read more about retinitis pigmentosa.
How common is Refsum disease?
The prevalence of Refsum disease is unknown, although the condition is thought to be uncommon.
What genes are related to Refsum disease?
More than 90 percent of all cases of Refsum disease result from mutations in the PHYH gene. The remaining cases are caused by mutations in a gene called PEX7.
The signs and symptoms of Refsum disease result from the abnormal buildup of a type of fatty acid called phytanic acid. This substance is obtained from the diet, particularly from beef and dairy products. It is normally broken down through a process called alpha-oxidation, which occurs in cell structures called peroxisomes. These sac-like compartments contain enzymes that process many different substances, such as fatty acids and certain toxic compounds.
Mutations in either the PHYH or PEX7 gene disrupt the usual functions of peroxisomes, including the breakdown of phytanic acid. As a result, this substance builds up in the body's tissues. The accumulation of phytanic acid is toxic to cells, although it is unclear how an excess of this substance affects vision and smell and causes the other specific features of Refsum disease.
How do people inherit Refsum disease?
This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.
Where can I find information about diagnosis or management of Refsum disease?
These resources address the diagnosis or management of Refsum disease and may include treatment providers.
General information about the diagnosis and management of genetic conditions is available in the Handbook. Read more about genetic testing, particularly the difference between clinical tests and research tests.
To locate a healthcare provider, see How can I find a genetics professional in my area? in the Handbook.
Where can I find additional information about Refsum disease?
You may find the following resources about Refsum disease helpful. These materials are written for the general public.
You may also be interested in these resources, which are designed for healthcare professionals and researchers.
What other names do people use for Refsum disease?
What if I still have specific questions about Refsum disease?
Where can I find general information about genetic conditions?
The Handbook provides basic information about genetics in clear language.
These links provide additional genetics resources that may be useful.
What glossary definitions help with understanding Refsum disease?
acids ; anosmia ; arrhythmia ; ataxia ; autosomal ; autosomal recessive ; breakdown ; cell ; dysplasia ; fatty acids ; gene ; hereditary ; ichthyosis ; inherited ; leukodystrophy ; motor ; neuropathy ; oxidation ; peripheral ; peroxisomes ; prevalence ; recessive ; retina ; sensory neuropathy ; sign ; syndrome ; toxic ; wasting
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
See also Understanding Medical Terminology.
References (8 links)
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook.