Symptomatic renal tubular acidosis (RTA) in patients with systemic lupus erythematosus: an analysis of six cases with new association of type 4 RTA

Objectives. We have analysed the association between different parameters of renal tubular acidosis (RTA) with clinical and laboratory parameters in patients with systemic lupus erythematosus (SLE). Methods. Review of hospital database records between 1978 and 2003 revealed six SLE patients with RTA. Correlations and comparisons were done by Spearman rank correlation coefficient and the χ2 test. Results. Four patients had hypokalaemia (type 1 RTA) and two patients had hyperkalaemia (type 4 RTA). Three patients with type 1, but no patients with type 4 RTA, had medullary nephrocalcinosis. The majority of SLE patients with distal RTA (type 1 and type 4) had nephritis with proteinuria. No seronegative SLE was noted, and all patients were negative for anticardiolipin antibodies. There was a noticeable trend of higher serum potassium levels with increased SLE Disease Activity Index (SLEDAI; P