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DOI: 10.1055/a-2055-1051
The Value of a Combined Ophthalmogenetic Approach in Differentiating a Presumed Case of Isolated Retinitis Pigmentosa from Refsum Disease
Der Wert eines kombinierten ophthalmogenetischen Ansatzes zur Unterscheidung einer vermuteten Refsum-Krankheit bei einem mutmaßlichen Fall von „isolierter“ Retinitis pigmentosa
Introduction
Refsum disease, also known as heredopathia atactica polyneuritiformis (OMIM 266 500), is a rare genetic disorder that is inherited in an autosomal recessive manner.
This syndromic disease has long been described with late-onset retinitis pigmentosa, and variable combinations of anosmia, polyneuropathy, deafness, ataxia, ichthyosis, cardiac arrhythmia, and heart failure [1], [2]. The presence of increased phytanic acid levels in tissues and plasma has been attributed to the presence of Refsum disease. This pathognomonic finding is due to defective α-oxidation pathway of branched chain fatty acids in the peroxisome [3]. Normal people have been considered to have undetectable levels of phytanic acid.
Patients with Refsum disease are unable to metabolize the daily intake (50 – 100 mg) of phytanic acid due to impaired phytanoyl-CoA 2-hydroxylase (PHYH/PAHX) activity. This enzyme catalyzes the first α-oxidative step in the catabolism of phytanic acid to pristanic acid, which is then further catabolized by peroxisomal β-oxidation. In patients with Refsum disease, an ω-oxidative route is activated to degrade phytanic acid [3].
However, this alternative route is limited to about 10 mg daily and therefore phytanic acid accumulates in various tissues in the body thought to be leading to the clinical manifestations of this peroxisomal disorder [2]. Patient management includes a diet free of chlorophyll and monthly or bimonthly plasmapheresis to remove phytanic acid from the body.
Retinitis pigmentosa is usually diagnosed years before the Refsum disease is confirmed genetically [2].
Publication History
Received: 16 October 2022
Accepted: 09 March 2023
Article published online:
25 April 2023
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