Refsum Disease is a progressive neurodegenerative disorder characterized by the gradual loss of neuronal function. This page provides comprehensive information about the disease, including its pathophysiology, clinical presentation, diagnosis, and current therapeutic approaches.
Refsum disease, also known as heredopathia atactica polyneuritiformis, is a rare autosomal recessive peroxisomal disorder characterized by a accumulation of phytanic acid in tissues and plasma due to impaired fatty acid oxidation. This leads to a progressive neurodegenerative syndrome featuring retinitis pigmentosa, peripheral neuropathy, cerebellar ataxia, and hearing loss.[1] [2]
Refsum disease was first described by Sigvald Refsum in 1946 as a familial syndrome combining retinitis pigmentosa, peripheral neuropathy, ataxia, and elevated cerebrospinal fluid protein. It is classified as a peroxisomal biogenesis disorder and represents one of the few treatable causes of hereditary ataxia, as dietary phytanic acid restriction can significantly alter the disease course.[2:1] [3]
The disease is rare, with an estimated prevalence of 1 in 1,000,000 individuals worldwide. However, certain populations show higher frequencies due to founder mutations, particularly in Norway and other Scandinavian countries.[3:1] [4]
Refsum disease is caused by homozygous or compound heterozygous mutations in the PAHX gene (peroxisomal 2-hydroxyacyl-CoA lyase), located on chromosome 10p13. This gene encodes the enzyme phytanoyl-CoA hydroxylase, which is essential for the peroxisomal oxidation of phytanic acid, a branched-chain fatty acid derived from dietary sources.[4:1] [5]
More recently, mutations in the PEX7 gene (peroxisome biogenesis factor 7) have been identified in some patients with Refsum disease phenotypes, particularly those with additional features like rhizomelic chondrodysplasia punctata.[5:1] [^6]
Phytanic acid (3,7,11,15-tetramethylhexadecanoic acid) is a branched-chain fatty acid found primarily in dairy products, ruminant fats, and some fish oils. Normal metabolism occurs via: [^7]
In Refsum disease, the deficient enzyme causes: [^8]
The traditional presentation includes four cardinal features: [^9]
| Feature | Description | Frequency |
|---|---|---|
| Retinitis pigmentosa | Progressive vision loss, tunnel vision, nyctalopia (night blindness) | 100% |
| Peripheral neuropathy | Motor and sensory neuropathy, distal weakness, reduced reflexes | 95% |
| Cerebellar ataxia | Gait instability, dysmetria, dysarthria | 90% |
| Sensorineural hearing loss | Progressive hearing impairment | 85% |
Without treatment:
With treatment, progression can be significantly slowed or halted.
[^8]
| Test | Finding |
|---|---|
| Plasma phytanic acid | Markedly elevated (100-3000 μmol/L) |
| Plasma pristanic acid | Normal or mildly elevated |
| Very-long-chain fatty acids | Normal |
| Pipecolic acid | Normal |
| Red blood cell plasmalogens | Normal |
| CSF protein | Elevated in 60% |
Phytanic acid restriction is the cornerstone of treatment:
| Food to Avoid | Alternatives |
|---|---|
| Dairy products (milk, cheese, butter) | Dairy-free alternatives |
| Ruminant meat (beef, lamb, goat) | Poultry, fish |
| Animal fats | Vegetable oils (except palm) |
| Certain fish (herring, mackerel) | Cod, haddock |
| Foods containing phytol | Avoid green leafy vegetables (cooked) |
With early diagnosis and strict dietary management:
Without treatment:
| Condition | Key Distinguishing Features |
|---|---|
| Usher syndrome | Retinitis pigmentosa + hearing loss, but no ataxia or elevated phytanic acid |
| Friedreich's ataxia | Ataxia + neuropathy + cardiomyopathy, but no retinitis pigmentosa |
| Ataxia with vitamin E deficiency | Low vitamin E, different pattern of neurological involvement |
| Other peroxisomal disorders | Elevated VLCFA in Zellweger spectrum |
| Charcot-Marie-Tooth disease | Neuropathy without retinitis pigmentosa |
The study of Refsum Disease has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
This section highlights recent publications relevant to this disease.