Question
Pencilliosis
Answer
Penicilliosis (now more precisely termed talaromycosis, following reclassification of the causative organism) is a systemic, opportunistic fungal infection caused by Talaromyces marneffei (formerly Penicillium marneffei) — the only dimorphic member of this genus, existing as a mould at room temperature and converting to a yeast form at body temperature (37°C).
Epidemiology: endemic to Southeast Asia (notably Thailand, Vietnam, southern China) and parts of northeastern India, with a strong association to the local bamboo rat, which serves as a natural reservoir; infection is thought to be acquired by inhalation of environmental conidia (spores), possibly from soil disturbed by these rodents.
Clinical significance: an important AIDS-defining opportunistic infection in endemic regions, occurring almost exclusively in severely immunocompromised patients (particularly advanced HIV/AIDS with low CD4 counts) — presenting as a disseminated systemic illness with prolonged fever, weight loss, generalized lymphadenopathy, hepatosplenomegaly, and a characteristic umbilicated, molluscum-contagiosum-like papular skin rash, typically on the face and upper trunk — this skin lesion pattern is a valuable diagnostic clue distinguishing it from other opportunistic infections.
Laboratory diagnosis: microscopy/culture from blood, bone marrow, skin lesion scraping, or lymph node — demonstrating the characteristic dimorphic growth (mould at 25°C, showing typical Penicillium-like brush-shaped conidiophores with a distinctive diffusible red pigment; yeast at 37°C, showing oval-to-elongated cells that divide by fission rather than budding — a distinguishing microscopic feature from Histoplasma and other dimorphic fungal yeasts, which divide by budding); histopathology of affected tissue/skin biopsy.
Treatment: amphotericin B induction therapy followed by itraconazole maintenance/consolidation therapy; secondary prophylaxis (itraconazole) is continued in AIDS patients until adequate immune reconstitution with antiretroviral therapy, given the risk of relapse.