Question | Discussion | References | CME Credit

Case 4: A 32-Year-Old with Fever, Weight Loss, and Fatigue

You answered:

B Among patients with disseminated MAC, fewer than 45% will have blood cultures that turn positive within 21 days. Thus, if MAC is suspected, the patient should proceed to bone marrow aspirate and culture to improve the diagnostic yield.

This answer is incorrect. Mycobacterial blood cultures are the preferred method to diagnose disseminated MAC. More than 90% of patients with disseminated MAC will have a positive blood culture, and most turn positive within 14 days. Although a few reports exist of patients having a positive MAC culture from bone marrow when blood cultures failed to grow MAC, performing a bone marrow procedure to culture MAC is not recommended for routine cases since the yield on blood cultures is so high.

Choose another answer:

A The anemia would be unusual with MAC and would strongly suggest a diagnosis other than MAC.
C The 2002 U.S. Public Health Service 2002 Guidelines for Preventing Opportunistic Infections state that secondary prophylaxis (to prevent recurrence of disseminated MAC) may be discontinued in patients treated with HAART who have a sustained (greater than 6 months) increase in CD4 count to greater than 100 cells/mm3 if they have completed 12 months of MAC therapy and have no ongoing symptoms or signs attributable to MAC.
D The preferred therapy for disseminated MAC consists of clarithromycin (Biaxin), rifabutin (Mycobutin), and clofazimine (Lamprene). Recent studies have shown that clofazimine decreases the MAC relapse rate more than ethambutol (Myambutol) and thus it has replaced the ethambutol in the preferred MAC treatment regimen.

[Back to Case 4 Question | Go to Correct Answer]