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Objective Several studies have confirmed the remarkable observation that cumulative urinary potassium (K(+)) excretion is less in African-Americans than White Americans even when identical amounts of potassium are provided in the diet. This study was designed to examine whether this decrease in urinary potassium could be compensatory to an increase in gastrointestinal excretion of potassium in African-Americans. Methods Twenty-three young, healthy, normotensive participants of both sexes and races were placed on a fixed diet of 100 mEq per day of K(+) and 180 mEq per day of sodium (Na(+)) for 9 days. All urine and stool were collected daily and analyzed for electrolytes. Blood was obtained for determination of electrolytes, blood urea nitrogen (BUN), creatinine, glucose, insulin, renin, and aldosterone at the beginning and at the end of the study period. Results Cumulative urinary excretion of K(+) was significantly less in African-Americans (609 ± 31 mEq) compared with White Americans (713 ± 22 mEq, P = 0.015). There was no significant racial difference, however, in the cumulative gastrointestinal excretion of K (105 ± 11 versus 95 ± 9 mEq, P = 0.28) in African-Americans versus White Americans, respectively. Conclusion The racial difference in urinary K(+) handling manifested by decreased excretion of K(+) in African-Americans cannot be attributed to an increase in net gastrointestinal excretion of this cation.

Wegener's granulomatosis (WG) is a systemic, necrotizing, granulomatous vasculitis of unknown etiology. Approximately 75% of cases present as classic WG with both pulmonary and renal involvement, while the remaining 25% of patients present with a limited form with either predominantly upper or lower respiratory tract symptoms. Ninety percent of WG patients have circulating anti–neutrophil cytoplasmic antibodies (ANCA), and approximately 10% have both circulating ANCA antibodies and concomitant anti–glomerular basement membrane (anti-GBM) disease on renal biopsy. Virtually all of these patients also have circulating anti-GBM antibodies. While it has been reported that some patients with ANCA vasculitis have circulating anti-GBM antibodies, and patients with anti-GBM disease may have positive ANCA, review of the literature does not demonstrate other cases of biopsy-proven, simultaneous, ANCA-associated vasculitis and anti-GBM disease. We report a case of simultaneous, biopsy-proven, classic, ANCA-positive WG and anti-GBM disease, but without detectible circulating anti-GBM antibodies. We present findings characteristic of both WG and linear IgG deposition along the GBM suggesting concurrent anti-GBM disease, in the absence of detectable circulating anti-GBM antibodies. Possible theories to explain the absence of these antibodies are discussed.