The occurrence of renal involvement in primary Sjogren's syndrome: a study of 78 patients

Objective. To ascertain the occurrence of renal involvement in patients with primary Sjogren's syndrome (pSS). Methods. Urinary total protein excretion from 24 h urine collection, as well as urinary excretion rates of albumin, alpha-1 microglobulin (alpha 1m) and IgG from overnight 8 h collections, were determined from 78 pSS patients (75 females, three males). Urine acidification capacity after oral ammonium chloride load was tested in 55 of these patients. Results. Mild proteinuria (0.15-0.42 g/24 h) was observed in 34 patients (44%). Increased urinary excretion rates of albumin greater than or equal to 20 mu g/min), alpha 1m (greater than or equal to 7.0 mu g/min) or IgG (greater than or equal to 5.0 mu g/min) were detected in nine (12%), nine (12%) and 11 patients (14%), respectively. Latent or overt distal renal tubular acidosis (dRTA) was observed in 18 out of 55 patients with pSS (33%). These patients had a longer duration of the disease (10 +/- 4 vs 8 +/- 4 yr; P less than or equal to 0.05); they also had proteinuria (67 vs 27%; P less than or equal to 0.025) and hypertension (44 vs 14%; P less than or equal to 0.05) more frequently, and significantly higher serum creatinine (92 +/- 39 vs 78 +/- 13 mu mol/l; P less than or equal to 0.025) and serum beta-2 microglobulin (beta 2m) levels (3.3 +/- 1.6 g/l vs 2.6 +/- 0.6 g/l; P less than or equal to 0.025) as compared to patients with normal urine acidification capacity. Conclusions. Inadequate renal acidification capacity, as well as mild proteinuria, were frequently found in patients with PSS Those with dRTA bad longer disease duration, a higher level of serum beta 2m, and they had proteinuria and hypertension more frequently than those with normal renal acidification capacity.