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Refsum-Thiebaut Disease – Symptoms and Treatment

Refsum-Thiebaut disease is a rare hereditary metabolic disorder in which phytanic acid accumulates in the body, causing progressive damage to nerves, eyes, and muscles.

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Things worth knowing about "Refsum-Thiebaut Disease"

Refsum-Thiebaut disease is a rare hereditary metabolic disorder in which phytanic acid accumulates in the body, causing progressive damage to nerves, eyes, and muscles.

What is Refsum-Thiebaut Disease?

Refsum-Thiebaut disease (also known as Refsum disease or heredopathia atactica polyneuritiformis) is a rare, autosomal recessive inherited metabolic disorder belonging to the group of peroxisomal disorders. It is named after Norwegian neurologist Sigvald Refsum and French physician François Thiebaut. In this condition, the breakdown of phytanic acid – a branched-chain fatty acid derived from dietary sources – is impaired, leading to its toxic accumulation in various tissues and organs throughout the body.

Causes

The disease is caused by mutations in the PHYH gene (phytanoyl-CoA hydroxylase) or, less commonly, in the PEX7 gene. These genes encode enzymes responsible for the alpha-oxidation of phytanic acid within peroxisomes. When these enzymes are deficient, phytanic acid cannot be properly broken down and accumulates in the blood, liver, kidneys, heart, and nervous tissue. Phytanic acid enters the body primarily through the consumption of dairy products, fatty fish, and certain plant-based foods containing chlorophyll.

Symptoms

Symptoms of Refsum-Thiebaut disease typically appear in adolescence or early adulthood and progress without treatment. Common manifestations include:

Retinitis pigmentosa: Progressive vision loss due to degeneration of the retina
Peripheral neuropathy: Tingling, numbness, and weakness in the arms and legs
Cerebellar ataxia: Balance disturbances and coordination difficulties
Anosmia: Loss of the sense of smell
Ichthyosis: Scaly, fish-like skin changes
Sensorineural hearing loss: Impaired hearing due to nerve damage
Cardiac arrhythmias: Heart rhythm abnormalities that may lead to cardiac failure
Skeletal abnormalities: Shortening of finger and toe bones (epiphyseal dysplasia)

Diagnosis

Diagnosis is based on a combination of clinical findings, laboratory tests, and genetic analysis:

Plasma phytanic acid levels: Markedly elevated concentrations (normal: below 0.3 mg/dL) are a hallmark finding
Neurological examination: Detection of ataxia and peripheral neuropathy
Ophthalmological assessment: Confirmation of retinitis pigmentosa
Electroretinogram (ERG): Functional evaluation of the retina
Nerve conduction studies (NCS): Measurement of peripheral nerve conduction velocity
Molecular genetic testing: Identification of mutations in the PHYH or PEX7 gene

Treatment

There is currently no curative treatment for Refsum-Thiebaut disease. Management focuses on lowering plasma phytanic acid levels and preventing further organ damage.

Dietary Therapy

The most important therapeutic measure is a lifelong low-phytanic acid diet. Foods rich in phytanic acid must be significantly restricted or avoided, including:

Fatty fish (e.g., salmon, tuna, sardines, herring)
Dairy products such as milk, cheese, and butter
Lamb and beef (in large quantities)
Foods rich in chlorophyll (in excessive amounts)

Plasmapheresis

In cases of acute deterioration or very high phytanic acid levels, plasmapheresis (plasma exchange) can be used to rapidly remove phytanic acid from the bloodstream. This method is used as a complement to dietary management.

Symptomatic Treatment

Additional treatment involves coordinated care from neurologists, cardiologists, and ophthalmologists, as well as physiotherapy to maintain mobility. Cardiac arrhythmias may be managed with medication or a pacemaker if necessary.

Prognosis

With consistent dietary management and regular medical follow-up, disease progression can be significantly slowed or halted. Existing nerve damage is generally not fully reversible; however, some symptoms such as neuropathy and ataxia may partially improve with good metabolic control. Rapid or sudden weight loss should be avoided, as the breakdown of adipose tissue – a storage site for phytanic acid – can release large amounts of the acid into the bloodstream and trigger acute worsening.

References

Wanders RJ, Waterham HR, Leroy BP. Refsum Disease. In: Adam MP et al. (eds.): GeneReviews. University of Washington, Seattle, 1993–2023. Available at: https://www.ncbi.nlm.nih.gov/books/NBK1353/
Skjeldal OH, Stokke O, Refsum S et al. Clinical and biochemical heterogeneity in conditions with phytanic acid accumulation. Journal of the Neurological Sciences, 1987; 77(1):87–96.
Steinberg D. Refsum Disease. In: Scriver CR et al. (eds.): The Metabolic and Molecular Bases of Inherited Disease. 8th edition. McGraw-Hill, New York, 2001.

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