Mycoplasma pneumoniae-associated nephritis in children

Mycoplasma pneumoniae infection is a rare cause of acute nephritis. Six children (2 girls) aged 5-10 years, admitted for nephritis, had serological tests showing recent Mycoplasma pneumoniae infection. The diagnosis of Mycoplasma pneumoniae infection was based on the presence of serum IgM, detected either by immunofluorescence (IF) (n = 1) or enzyme-linked immunosorbent assay (n = 5). Four children had a renal biopsy, with analysis of parenchymal Mycoplasma pneumoniae components by indirect IF and polymerase chain reaction. Extrarenal symptoms were: respiratory (n = 3), ear, nose and throat (n = 2), gastrointestinal (n = 3), hepatic (n = 1), neurological (n = 1), articular (n = 1), and hematological (n = 3). The patients presented with acute nephritis (1 had a nephrotic syndrome) or with acute renal failure and proteinuria. Pathological findings included type 1 membranoproliferative glomerulonephritis (MPGN, n = 1), proliferative endocapillary glomerulonephritis (n = 2) and minimal change disease (n = 1). The patient with type 1 MPGN progressed rapidly towards end-stage renal failure because of a congenital solitary kidney. Among the patients with endocapillary glomerulonephritis, 1 relapsed 6 months later and remained proteinuric, while the other recovered, as did the child with minimal change disease. The search for Mycoplasma pneumoniae antigens and nucleic acids in renal tissue was negative. However, the absence of the microorganism in the kidney is a common feature of post-streptococcal glomerulonephritis. We conclude that Mycoplasma pneumoniae is a rare yet potential cause of acute glomerulonephritis.