Clinical linoleic acid deficiency in Dahl salt-sensitive (SS/Jr) rats

Male SS/Jr rats were placed on a specially formulated, high-cholesterol, low-sodium diet at 3 weeks of age. Of the 50 animals on the diet, 40 developed skin lesions ranging from focal areas of alopecia to diffuse areas of moist dermatitis on the head, face, ear pinnae, and neck. Similar lesions were noted later in 17 of 36 SS/Jr rats in a second study group. Histopathologic findings from two affected animals revealed diffuse, hyperplastic, ulcerative dermatitis, with bacterial colonies of cocci in superficial crusts, as well as chronic hepatic inflammation with hepatocellular glycogen and sinusoidal macrophage aggregates suggestive of lipidosis. Results of a fatty-acid profile of the affected rats showed serum linoleic acid levels of 931 to 1566 micromol/liter, whereas those for control (SS/Jr) samples ranged from 2711 to 3145 micromol/liter. Dietary analysis of the specially formulated diet showed that it contained only 0.225% linoleic acid, which is below the recommended level of 0.3 to 0.6%. In light of the clinical and dietary findings, a diagnosis of linoleic acid deficiency was made. The food manufacturer revised its dietary formulation to increase the linoleic acid content to 1.05%, and no further cases of dermatitis developed in any subsequent groups of rats maintained under the same study protocol.