Which of the following is false regarding dimorphic fungi –
**Core Concept**
Dimorphic fungi are a group of fungi that can exist in two forms: a yeast form and a filamentous or mold form. This dimorphism is typically temperature-dependent, with the yeast form being the pathogenic form that causes disease in humans. The most common dimorphic fungi include *Histoplasma capsulatum*, *Blastomyces dermatitidis*, *Coccidioides immitis*, and *Paracoccidioides brasiliensis*.
**Why the Correct Answer is Right**
The ability of dimorphic fungi to exist in both yeast and mold forms is critical for their pathogenesis. At a temperature of around 37°C (98.6°F), these fungi convert from a mold form to a yeast form, which is more virulent and capable of infecting mammalian hosts. This temperature-dependent dimorphism is a key characteristic of these fungi and is essential for their ability to cause disease.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because dimorphic fungi do indeed have a temperature-dependent dimorphism, with the yeast form being the pathogenic form. The mold form is typically the saprophytic form that grows in the environment.
**Option B:** This option is incorrect because the yeast form of dimorphic fungi is the pathogenic form that causes disease in humans, not the mold form.
**Option C:** This option is incorrect because the dimorphism in these fungi is temperature-dependent, not pH-dependent.
**Clinical Pearl / High-Yield Fact**
A key clinical correlation to remember is that patients with dimorphic fungal infections often have a history of exposure to soil or other environmental sources, and the infection may be exacerbated by underlying immunocompromised conditions.
**Correct Answer:** C.