A Case of Distal Renal Tubular Acidosis with Systemic Lupus Erythematosus (SLE)

ABSTRACT

Distal renal tubular acidosis (RTA) is well-recognized complication of immunologically mediated condition such as Sj ogren's syndrome, SLE, idiopathic hypergammaglobulinemia, autoimmune liver disease, autoimmune thyroid disease, multiple myeloma, and renal tranplant rejection. Tubulointerstitial involvement frequently occurrs in SLE. A sepctrum of abnormalities including impaired uriary concentration or acidification, increased fractional excretion of low molecular weight protein, hyporeinaemic hypoaldosteroniam and impaired tubular potassium excretion can occur in SLE. But complete distal RTA associated wih SLE is rare. We report a 13 year-old female with SLE and distal RTA which was diagnosed by NaHCO3 loading test. She had nephrotic syndrome, hypokalemia, hyperchloremic metabolic acidosis with alkali urine. She had fatiquebility, general weakness, intermittent fever and chest pain for at least 12months. And then, the butterfly-shaped malar rash was developed, so pediatrician suspected SLE and she was refer to us. At hospitalization. She had malar rash, percardial effusion, persistent proteinuria greater than 3+, hemolytic anemia, lymphopenia, leukopenia, positive LE cell, Anti-DNA Ab and posotive ANA. So her clinical data are satisfied ARA criteria for SLE. Her renal biopsy showed diffuse proliferative SLE nephpritis and marked focal tubular atrophy with localized heavy mononuclear cell infiltration and fibrosis. We performed NaHCO3 loading test to confirm distal RTA. During the test, we detected the inability to achieve a high urinary PCO2. This result is the most sensitive index of impaired distal acidification, so we can diagnose distal RTA. She had a good response to the therapy with prednisolone NaHCO3 and oral KCL supplement.