Background: Talaromyces marneffei is an opportunistic pathogen that infects immunodeficient and immunocompromised patients. We presented a pediatric patient with a diagnosis of T. marneffei infection who was followed up in the Guangzhou Women and Children’s Medical Centre. Case presentation: The child was a 5-year-old girl with persistent cough and gasping over 2 months who was confirmed with T. marneffei infection by bronchoalveolar lavage fluid culture and high-throughput sequencing technology. Human immunodeficiency virus (HIV) was negative according to a serum-specific antibody test. She was treated with amphotericin B and itraconazole as antifungal agents, with good clinical response. At follow-up, high-resolution computed tomography showed a mosaic sign in the whole lung field with a diagnosis of post-infectious bronchiolitis obliterans (PIBO) as the sequela. She has a mutated COPA gene with uncertain pathogenic potential on whole-exome sequencing. Conclusions: Clinicians should consider PIBO as a possible sequela in an HIV-negative paediatric patient with T. marneffei infection.

Background: Chronic granulomatous disease (CGD) is a rare primary immunodeficiency disorder caused by defects in phagocyte NADPH oxidase. X-linked CGD, resulting from CYBB gene mutations, accounts for approximately two-thirds of cases. Clinical manifestations typically include recurrent bacterial and fungal infections, granuloma formation, and inflammatory complications. Case presentation: We report monochorionic diamniotic twins with a novel CYBB variant (c.1303A > T, p.Lys435Ter). The 7-month-old proband presented with recurrent respiratory infections and was initially misdiagnosed with congenital cystic lung disease. His twin brother carried the identical mutation but remained asymptomatic. Neutrophil function testing demonstrated impaired respiratory burst activity. Whole-exome sequencing confirmed a de novo nonsense mutation in the CYBB gene. Conclusions: This case highlights the diagnostic challenges of CGD and illustrates remarkable phenotypic discordance in monochorionic twins with identical genetic mutations. Environmental factors and epigenetic modifications may contribute to variable expressivity. Early genetic testing is crucial for accurate diagnosis and appropriate management of suspected primary immunodeficiency disorders.