Septate hyphae are a characteristic feature of which genus commonly implicated in allergic lung disease?

• A. Candida albicans
• B. Cryptococcus neoformans
• C. Aspergillus
• D. Histoplasma capsulatum

Answer: (C)

Septate hyphae indicate a mold with cross-walled filaments, and among fungi linked to allergic lung disease, Aspergillus is the classic example. It forms septate hyphae that branch dichotomously at acute angles, and inhaled Aspergillus antigens can provoke allergic bronchopulmonary aspergillosis, an IgE-mediated hypersensitivity reaction seen in patients with asthma or cystic fibrosis. This contrasts with Candida albicans, which grows as yeast with pseudohyphae; Cryptococcus neoformans, a encapsulated yeast; and Histoplasma capsulatum, which is typically seen as intracellular yeast within macrophages. Thus, the genus associated with septate hyphae and allergic lung disease is Aspergillus.