Article in Japanese

The case of a young boy with pneumococcal bacteremia associated with transient hypocomplementemia due to post-streptococcal acute glomerulonephritis:A case report and review of the literature

Kentaro Matsumura^1）, Sohsaku Yamanouchi^1）, Taichi Ohmachi^1）, Shogo Kato^1）, Shoji Tsuji^1）, Kazunari Kaneko^1）

Post-streptococcal acute glomerulonephritis （PSAGN） is characterized by the acute onset of hematuria, proteinuria, oliguria, and edema, accompanied by transient hypocomplementemia. Invasive bacterial infections in patients with complement deficiencies are typically caused by encapsulated bacteria such as Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis, particularly in cases of C3 deficiency.
This study reports the case of a 5-year-old boy who developed pneumococcal bacteremia associated with hypocomplementemia due to PSAGN. Although he had already received the 13-valent pneumococcal conjugate vaccine, the Streptococcus pneumoniae isolated from his blood culture was a non-vaccine serotype.
The opsonization and bacteriolysis mediated by the alternative pathway, initiated by C3, are crucial components of the host defense mechanism against Streptococcus pneumoniae. It was speculated that due to PSAGN the transient C3 hypocomplementemia impaired these processes, and in this case led to the development of pneumococcal bacteremia together with the absence of antibodies against invasive pneumococcus.
In conclusion, there should be a high index of suspicion for concurrent invasive bacterial infection when fever presents in a patient with PSAGN-induced hypocomplementemia.

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1）Department of Pediatrics, Kansai Medical University

Key words	post-streptococcal acute glomerulonephritis, C3 hypocomplementemia, pneumococcal conjugate vaccine, invasive pneumococcal disease, pneumococcal bacteremia
Received	October 30, 2025
Accepted	February 7, 2026

38 (1)：27─32,2026