Familial Mediterranean fever in a fraternal twin: a laboratory evaluation.

Familial Mediterranean fever (FMF) is an autosomal recessive disease of unknown etiology and has no known diagnostic markers. Periodic attacks of pain and fever can be precipitated by dietary fat or dairy products and by the same factors that are known to elevate serum free fatty acids (FFA). Several tests related to lipid metabolism were made on the serum and urine of a fraternal twin with FMF during attacks and remission. The results were compared with those of the unaffected, asymptomatic twin and healthy adults. Low density lipoprotein-cholesterol was elevated in both twins. Gas chromatography revealed many urinary FFA during attacks and fewer during remission. Urinary organic acids determined by gas chromatography/mass spectrometry (GC/MS) revealed slight elevations of glycollic, oxalic, and methylmalonic acids during an attack. Serum gamma-glutamyl transferase (GGT) levels were at or below the low limits of normal for both twins. Hematological studies revealed low values for erythrocyte parameters for the affected twin. Both twins had low serum iron and an increased iron binding capacity. These findings may represent a defect in fatty acid metabolism which is being compensated by alternate pathways which may generate oxidants. Both FFA and oxidants are injurious to cell membranes and may be the cause of the polyserositis which occurs during an attack.