Phytanic acid oxidase deficiency

A rare metabolic disorder affecting the breakdown of phytanic acid

Phytanic acid oxidase deficiency
Synonyms	N/A
Pronounce	N/A
Specialty	N/A
Symptoms	Retinitis pigmentosa, peripheral neuropathy, ataxia, hearing loss
Complications	N/A
Onset	Childhood or adolescence
Duration	N/A
Types	N/A
Causes	Mutations in the PHYH gene
Risks	N/A
Diagnosis	Genetic testing, blood test for elevated phytanic acid
Differential diagnosis	N/A
Prevention	N/A
Treatment	Dietary restriction of phytanic acid, plasmapheresis
Medication	N/A
Prognosis	Variable, depends on management
Frequency	Rare
Deaths	N/A

Phytanic acid oxidase deficiency is a rare metabolic disorder characterized by the body's inability to properly break down phytanic acid, a type of branched-chain fatty acid found in certain foods. This condition is also known as Refsum disease, named after the Norwegian neurologist Sigvald Refsum who first described it.

Pathophysiology

Phytanic acid oxidase deficiency is caused by mutations in the PHYH gene, which encodes the enzyme phytanoyl-CoA hydroxylase. This enzyme is crucial for the alpha-oxidation of phytanic acid, a process that occurs in the peroxisome. When this enzyme is deficient or non-functional, phytanic acid accumulates in the body, leading to a variety of symptoms.

Symptoms

The accumulation of phytanic acid in tissues can lead to a range of clinical manifestations, including:

• Retinitis pigmentosa: Progressive vision loss due to degeneration of the retina.
• Peripheral neuropathy: Damage to the peripheral nerves causing weakness, numbness, and pain, usually in the hands and feet.
• Ataxia: Lack of voluntary coordination of muscle movements.
• Hearing loss: Sensorineural hearing impairment.
• Ichthyosis: Dry, scaly skin.

Diagnosis

Diagnosis of phytanic acid oxidase deficiency is typically based on clinical symptoms, family history, and laboratory tests. A blood test can reveal elevated levels of phytanic acid. Genetic testing can confirm mutations in the PHYH gene.

Treatment

Management of phytanic acid oxidase deficiency involves dietary restriction of phytanic acid. Patients are advised to avoid foods high in phytanic acid, such as dairy products, beef, lamb, and certain fish. In some cases, plasmapheresis may be used to reduce phytanic acid levels in the blood.

Prognosis

The prognosis for individuals with phytanic acid oxidase deficiency varies. Early diagnosis and strict dietary management can help prevent or mitigate symptoms. However, if left untreated, the condition can lead to significant disability.

Also see

• Peroxisomal disorder
• Metabolic disorder
• Retinitis pigmentosa
• Peripheral neuropathy

NIH genetic and rare disease info

• NIH info on Phytanic acid oxidase deficiency

Phytanic acid oxidase deficiency is a rare disease.