A Review of Fungal Infections for the Physician Assistant Exam
The fungal infections covered on the Physician Assistant Exam (PANCE) can be serious, causing bacteremia as well as affecting specific organs, including the lung. Some of the organisms are opportunistic infections. For the PANCE, you should be aware of four different fungal conditions: pneumocystis, histoplasmosis, cryptococcosis, and candidiasis. You see several of these with increasing prevalence with an advanced HIV infection.
Pneumocystis jirovecii (formerly known as Pneumocystis carinii) is an infection in the lung, usually in people who are immunosuppressed. A common clinical test scenario involves someone who’s a solid organ transplant patient or who has advanced HIV and presents with shortness of breath.
Here are some key points concerning Pneumocystis jirovecii:
It’s often seen in an HIV patient with a CD4 count of 250 or less.
A chest radiograph can show diffuse bilateral infiltrates. This pneumonia can be very destructive.
This pneumonia can be characterized by an elevated LDH level.
The initial treatment of choice is intravenous trimethoprim/sulfamethoxazole (Bactrim). If the patient has a sulfa allergy, the next treatment of choice is pentamidine.
If you encounter a test question in which the person is hypoxemic with a very low pO2 and low oxygen saturation, he or she needs intravenous steroids in addition to the trimethoprim/sulfamethoxazole.
Histoplasmosis is also known as Ohio Valley disease or cave disease. It mainly affects the lungs. If a test question mentions that the patient lives (or has lived) in the Ohio River Valley or near the Mississippi River, start thinking about histoplasmosis. The person presents with shortness of breath and may have a cough or flu-like symptoms.
Histoplasmosis is caused by Histoplasma capsulatum, a fungus that’s found in soil that contains infected bird or bat feces. Here are some key points about histoplasmosis:
Histoplasmosis primarily affects the lung. The chest radiograph can show a bullet-like appearance.
Histoplasmosis can affect areas other than the lungs, producing bone and joint infections and pericarditis.
The person can be put on oral itraconazole if he or she is an outpatient. If the person is admitted to the hospital, he or she is put on amphotericin B.
Cryptococcus infection is caused by the fungus Cryptococcus neoformans. A common clinical scenario involves someone with a headache with fever and nuchal rigidity. For PANCE purposes, be aware that Cryptococcus can cause a severe form of meningitis, especially in people who are immunosuppressed. The treatment is amphotericin B initially and then an oral fluconazole (Diflucan).
Which one of the following is an adverse effect associated with amphotericin B?
(A) Heart failure
(B) Liver failure
(C) Bone marrow toxicity
(D) Kidney failure
(E) Lung fibrosis
The correct answer is Choice (D). In someone who’s being treated with amphotericin B, the main side effect is kidney disease. In addition, the drug can cause low potassium and low magnesium. Anyone on amphotericin B needs to be treated with intravenous saline to reduce the risk of kidney disease.
Candidiasis is a fungal infection produced mainly by Candida albicans, although there are many species of Candida. In someone with uncontrolled diabetes, the first manifestation can be recurrent fungal or yeast infections. People who are immunosuppressed can have Candida esophagitis. And this fungus is one of three big causes of vaginitis. It looks wretched on the tongue or skin.
In addition to diabetes and immunosuppression (think HIV here as well), another risk factor is overuse of antibiotics. Antibiotics can really disrupt bowel flora and promote candidal overgrowth. Total parenteral nutrition (TPN) can also increase the risk of getting a fungal infection.
For Candida vulvovaginitis, the recommended treatment is one dose of fluconazole (Diflucan) 150 mg or a topical miconazole cream (Monistat) applied twice a day. For Candida-induced esophagitis, the recommended treatment is intravenous fluconazole (Diflucan).