Inherited tapetoretinal degenerations associated with, or caused by, abnormalities in lipid metabolism are discussed in terms of recent findings regarding their etiology. The biochemical basis of these tapetoretinal degenerations may be summarized as follows.(a) In abetalipoproteinemia (the Bassen-Kornzweig syndrome) there is a complete absence of all plasma lipoproteins except HDL (alfalipoprotein; high density lipoprotein). In addition the levels of plasma lipids, including vitamin A, are grossly dimished. The genetically-caused basic defect in this disorder is the absence of a specific protein component, apoLP-ser, in the plasma lipoproteins.(b) In a milder form of hypobetalipoproteinemia, transmitted as an autosomal dominant trait, there is little, if any, retinal degeneration.(c) Refsum's syndrome is characterized by greatly increased plasma levels of phytanic acid, a 20-carbon branched-chain fatty acid. This substance is not synthesized in the body, but originates from dietary sources only. Patients with Refsum's syndrome lack the enzyme (phytanic acid oxidase) necessary to oxidize this fatty acid, and its accumulation in the tissues has severe consequences. Therapeutic measures, consisting of restriction of dietary phytanic acid, have given encouraging results.(d) Three forms of Batten's disease (neuronal ceroid lipofuscinosis) are now recognized. These are (1) the rapidly progressive (Jansky-Bielschowsky) form, (2) the chronic (Batten-Mayou-Vogt-Spielmeyer-Sjögren) form, which is the most common, and (3) the late onset (Kufs') form. All are associated — to varying degrees — with an accumulation of autofluorescent ceroidlipofuscin pigments. The enzymatic defect is believed to consist of abnormalities in peroxidase enzymes.(e) Other tapetoretinal degenerations thought to be associated with defects in lipid metabolism are discussed briefly. These include Hooffs disease, Cockayne's syndrome, and Alstrom's syndrome.
Phytanic acid-derived peroxisomal lipid metabolism in porcine oocytes
