To the Editor—
Fisher's statement about the cross reaction of glyceryl p-aminobenzoic acid (PABA) with p-aminosalicylic acid, p-phenylenediamine, procaine, and sulfa derivatives should be of interest to clinicians (Archives 113:1299-1300, 1977).It is well known that lupus and lupus-like syndromes are more frequently diagnosed presently than in the past.Procainamide has been incriminated in most reported cases of druginduced systemic lupus erythematosus (SLE). It does not seem to be just an idiosyncratic reaction because the clinical signs appear in 20% to 30% of patients taking the drug.1,2 Serological abnormalities occur in 50% or more of patients treated for six weeks or longer.3It is important to point out that 60% of procainamide (p-amino-N-[2-diethylaminoethyl] benzamide) is excreted by the kidneys. Two percent to 10% is recovered in the urine as free and as conjugated PABA,4 which have some structural similarities to salicylic acid (orthohydroxybenzoic acid),
Pereyo-Torrellas N. p-Aminobenzoic-Acid-Related Compounds and Systemic Lupus. Arch Dermatol. 1978;114(7):1097. doi:10.1001/archderm.1978.01640190075040
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