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 chi(2) 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 < 0.1) and nephritic manifestation (haematuria, P < 0.1). The mean SLEDAI scores were 11.75 and 27.5 for type 1 and type 4 RTA patients, respectively.
Conclusions: When present in patients with SLE, classic distal RTA (type 1) is the most common. In particular, we report here for the first time two cases of type 4 RTA in SLE patients with higher SLEDAI scores than patients with type 1 RTA. Medullary nephrocalcinosis or renal urolithiasis has not been found in our patients with type 4 RTA. Higher serum potassium levels seem to be associated with higher SLEDAI scores and more severe nephritic manifestations in patients with distal RTA.