Question

A patient with cervical lymphadenopathy and is found to be retropositive. A fungal culture depicts a velvety growth with red diffusible pigment on the underside, as shown below. Which is the most likely causative organism?

• A. Talaromyces marneffei
• B. Blastomyces
• C. Aspergillus
• D. Pneumocystis jirovecii

Answer 1

The Correct Option is A

A patient with cervical lymphadenopathy who is retropositive (HIV positive) presents with a fungal culture showing a velvety growth and red diffusible pigment on the underside. This clinical presentation and laboratory finding are characteristic of one specific organism: Talaromyces marneffei.
Let's analyze the given options based on this information:

1. Talaromyces marneffei: Known to cause infection predominantly in immunocompromised patients, such as those with HIV. It exhibits a characteristic morphology with a velvety colony appearance and produces a red diffusible pigment on culture.
2. Blastomyces: Typically does not produce a red diffusible pigment. It is associated with systemic mycoses, but its colony morphology and pigmentation differ from Talaromyces marneffei.
3. Aspergillus: Known for septate hyphae but does not produce a red pigment. Aspergillus species usually have a granular or powdery colony appearance.
4. Pneumocystis jirovecii: A fungus causing pneumonia in immunocompromised individuals but cannot be cultured in the laboratory like typical fungi, and it does not exhibit the described colony morphology.

Considering the clinicopathological correlation, the distinctive combination of the patient's retropositive status, the appearance of the velvety growth, and the red diffusible pigment leads to the conclusion that the causative organism is Talaromyces marneffei.