Salt loss and hyponatraemia in a patient with syphilitic nephritis

The relationship between syphilis and nephropathy has been recognized for >100 years [1]. Nephropathy may appear in either congenital syphilis or the secondary stage of an acquired infection [2,3]. Nephropathy is an infrequent complication of acquired syphilis but may develop clinically in the secondary stage of the infection [3]. Most patients display a nephrotic syndrome [4]. Membranous glomerulonephritis or diffuse endocapillary glomerulonephritis with or without crescent formation were the main pathological findings in adults with acquired syphilis [5]. Interstitial nephritis, being the dominant feature, was rarely documented in the literature. We report an unusual occurrence of secondary syphilis with interstitial nephritis due to recurrent hyponatraemia from salt-losing nephropathy. Penicillin treatment completely resolved the salt-losing nephropathy and intractable hyponatraemia.