Opportunistic infections associated with extremely low-dose adrenocorticotropic hormone therapy: Two cases of Legionella and Pneumocystis carinii pneumonia

Adrenocorticotropic hormone (ACTH) therapy, the first-line treatment for infantile spasms, is known to dose-dependently increase incidences of infectious diseases. Extremely low-dose ACTH therapy is considered safe, and there have been no reports of opportunistic or other serious infections associated with this therapy. Herein, we report two cases of Legionella and Pneumocystis carinii pneumonia associated with extremely low-dose ACTH therapy. Patient 1 with PIGA variant was administered extremely low-dose ACTH therapy at 6 months, developing pneumonia 2 weeks after therapy initiation; Legionella pneumonia diagnosis was confirmed 14 days after onset. Although minocycline, ciprofloxacin, azithromycin, and rifampicin were administered, pneumonia progressed critically and required prolonged intensive care, resulting in chronic respiratory failure. Patient 2 with KLHL20 variant was administered extremely low-dose ACTH therapy for 4 weeks at the age of 3 months, developing Pneumocystis carinii pneumonia 1 week after completion of therapy, which recovered with trimethoprim-sulfamethoxazole therapy. Extremely low-dose and short-term ACTH therapy can be associated with opportunistic infections, and early diagnosis and treatment are crucial, because delays in administering appropriate antibiotics can lead to severe complications.