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.

Different Conditions

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Disorders of peroxisomal alpha-, beta- or omega-oxidation

Refsum disease, a very rare disease, biochemically characterised by phytanic acid accumulation, belongs to the group of leukodystrophic diseases. The first symptom is hemeralopia (loss of vision in the dark), followed by episods of chronic distal motor polyneuropathy. Other associated signs include perceptive deafness, anosmia, cerebellous ataxia and sometimes, severe intellectual deficiency.

Additional Information

Refsum disease, biochemically characterised by phytanic acid accumulation, belongs to the group of leucodystrophic diseases. Prevalence of the disease is of 1 case per 1 000 000 and males and females are equally affected. Initial signs usually appear around the age of 15, but they can also manifest during childhood or at the age of 30-40 years. The first symptom is hemeralopia (loss of vision in the dark), followed by episods of chronic distal motor polyneuropathy. Other associated signs include perceptive deafness, anosmia, cerebellous ataxia and sometimes, severe intellectual deficiency. Over the course of time cutaneous signs appear (ichtyosis), along with polyepiphyseal dysplasia, myocardiopathy, elevated protein in cerebrospinal fluid, and pigmentary retinitis that may result in blindness. Refsum disease is transmitted as an autosomal recessive trait. This disorder results from phytanic acid (3,7,11,15-tetramethylhexadecanoic acid) accumulation, which leads to lesions essentially in retina, brain and peripheral nervous system. In most cases, the causative mutation is in the PHYH gene (or PAXH, localised in 10pter-p11.2) encoding the peroxysomal enzyme phytanoyl-CoA hydroxylase (PhyH), which alpha-oxidises phytanic acid and allows the first step of its degradation. Another mutation was recently identified in PEX7 gene, localised in 6q22-24. It codes for the peroxine 7 receptor, which allows the import of PhyH in peroxysomes. Diagnosis is brought by the biologic evidence of phytanic acid in plasma and urines. Heterozygotes can be detected. As phytanic acid comes exclusively from food (green vegetables and herbivore animals), a strict diet helps symptoms regress partly. Nevertheless, altered audition and vision as well as anosmia can persist.

Organ Affected

Nerve structure (body structure)|Entire nerve (body structure)

Causes

defective oxydation of phytanic acid

Also Known As

  • Hereditary motor and sensory neuropathy type 4
  • Phytanic acid oxidase deficiency
  • Phytanic acid storage disease
  • Heredoataxia hemeralopica polyneuritiformis
  • Refsum-Thiebaut disease
  • HMSN 4 - [Hereditary motor and sensory neuropathy type 4]
  • Related ICD 10 COde
    ICD 10 Code G60.1

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