An adolescent case of anti-neutrophil cytoplasmic autoantibodies-associated crescentic glomerulonephritis complicated with subclinical autoimmune thyroiditis.

We report here a 15-year-old girl with myeloperoxidase anti-neutrophil cytoplasmic antibodies (MPO-ANCA)-associated crescentic glomerulonephritis (CreGN) and subclinical autoimmune thyroiditis. She was found to have proteinuria and hematuria by a school mass-screening a year before the first visit to the hospital, where a routine examination revealed blood urea nitrogen (BUN) 36.8 mg/dl and serum creatinine concentration of 1.63 mg/dl, although she had no apparent disabilities. On admission, the additional laboratory findings showed proteinuria of 1.06 g/day, hematuria of 3+, and a creatinine clearance of 30.1 ml/min. Hypocomplementemia was not observed. A renal biopsy revealed pauci-immune CreGN with 95% fibrocellular crescents, 84% sclerosis and/or hyalinosis and a massive cellular infiltration in the interstitium. She had MPO-ANCA of 865 EU/ml and an anti-thyroid microsome antibody titer of 1:1,600 without the detection of anti-glomerular basement membrane antibodies. Laboratory tests and scintigraphies for the thyroid gland did not show any abnormalities. Under the diagnosis of MPO-ANCA-associated CreGN, cocktail therapy consisting of prednisolone, cyclophosphamide, dilazep hydrochloride and warfarin was started. Improvement of urinary abnormalities and suppression of further deterioration of renal function were observed. Serial renal biopsy 6 months after the initiation of therapy showed decrement of interstitial cell infiltration and no generation of other crescentic glomeruli. The patient's serum titer of anti-thyroid microsome antibody was not affected by the adsorption of MPO-reacted IgG, suggesting that MPO-ANCA was not cross-reactive to thyroid microsome antigen.