A 32-year-old man was referred to a hematologist 6 months ago with complaints of fatigue, night sweats, and difficulty breathing while lying supine. He also reported a 20 lb (9 kg) weight loss over the last 6 weeks, although he denied any alterations in his diet. On physical examination, enlarged lymph nodes were palpated in his neck and groin and a complete diagnostic work-up was ordered. Pathology slides revealed Reed Sternberg cells and a diagnosis of Hodgkin's lymphoma was made. The patient then began an aggressive chemotherapy regimen. During one of his treatment cycles, the patient experiences fever, dyspnea, and malaise. Blood cultures incubated for 3 hours at 37 C (98.6 F) reveal the following findings: Which of the following is the most likely cause of this patient's condition?

Question

A 32-year-old man was referred to a hematologist 6 months ago with complaints of fatigue, night sweats, and difficulty breathing while lying supine.  He also reported a 20 lb (9 kg) weight loss over the last 6 weeks, although he denied any alterations in his diet.  On physical examination, enlarged lymph nodes were palpated in his neck and groin and a complete diagnostic work-up was ordered.  Pathology slides revealed Reed Sternberg cells and a diagnosis of Hodgkin's lymphoma was made.  The patient then began an aggressive chemotherapy regimen.  During one of his treatment cycles, the patient experiences fever, dyspnea, and malaise.  Blood cultures incubated for 3 hours at 37 C (98.6 F) reveal the following findings:  Which of the following is the most likely cause of this patient's condition?

Quizplus · Accepted Answer

Candida fungi exist in yeast (single cell) form. On light microscopy, they appear as budding yeasts with pseudohyphae. The germ tube test is diagnostic of Candida albicans, and allows it to be distinguished from other members of the Candida family (such as C. tropicalis and C. glabrata). Inoculation of Candida albicans into serum at 37 C (98.6 F) for 3 hours leads to the formation of true hyphae from the yeast, as shown in the microscopic image above. These growing hyphae are called "germ tubes." Candida species are a part of the normal human skin and mucous membrane flora. Candida can cause localized disease in immunocompetent people with decreased local defenses. Potential manifestations include: In immunocompromised patients, Candida can also cause disseminated disease that may affect any organ system. Potential manifestations include pneumonia, esophagitis, right-sided endocarditis, abscesses, and candidemia (sepsis). (Choices A and B) Rhizopus and Aspergillus exist only in mold form (forming true hyphae). Germ tubes are not seen. (Choice D) Cryptococcus neoformans classically causes meningitis and lung infections in AIDS patients. It is an oval budding yeast with a thick capsule that can mimic the appearance of Candida species, although Cryptococcus typically does not form hyphae or pseudohyphae. India ink stain of the CSF reveals a wide clear zone around the nucleus (corresponds to unstained capsule). (Choice E) Histoplasma capsulatum is a dimorphic fungus that exists in yeast form at body temperature. Microscopic examination of tissue specimens would reveal oval yeast cells within macrophages. Histoplasma does not form germ tubes. (Choice F) Coccidioides immitis is a dimorphic fungus that forms molds at 25 C (77 F), but exists as spherules in human tissues. Spherules are covered by a capsule and contain endospores. Germ tubes are not formed. Educational objective: Candida albicans is the most common cause of opportunistic mycosis. It can affect any organ and cause generalized candidemia. Yeasts and pseudohyphae on light microscopy and a positive germ tube test are diagnostic of Candida albicans infection. __________ References: Current treatment strategies for disseminated candidiasis. (http://www.ncbi.nlm.nih.gov/pubmed/16355336) Utility of the germ tube test for direct identification of Candida albicans from positive blood culture bottles. (http://www.ncbi.nlm.nih.gov/pubmed/18685004) Microbiology of systemic fungal infections. (http://www.ncbi.nlm.nih.gov/pubmed/16519250)

A 32-Year-Old Man Was Referred to a Hematologist 6 Months