
An HIV positive patient with a CD4 count of 300/Cumm is immunosuppressed, making them more susceptible to opportunistic infections. The presence of mucosal lesions in the mouth combined with the microscopy findings of budding yeasts and pseudohyphae strongly indicates an infection caused by a fungal organism.
The most common fungal infection in this scenario is caused by Candida species, which are responsible for oral candidiasis (also known as thrush). The description of "budding yeasts and pseudohyphae" is characteristic of Candida under a microscope.
Thus, the most probable diagnosis for the lesions described is:
Candidiasis





