Case Letter

Mycobacterium haemophilum: A Challenging Treatment Dilemma in an Immunocompromised Patient

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In addition to this change in antibiotic coverage, the patient’s medical oncologist tapered the patient’s immunosuppression considerably. The patient subsequently completed 12 months of therapy with clarithromycin, moxifloxacin, and rifabutin starting from the time of the neck biopsy. He remained free of recurrence of mycobacterial infection for nearly 2 years until he died from an unrelated illness.

Nontuberculous mycobacteria are an ubiquitous environmental group.2 Sources include soil and natural water (M avium), fish tanks and swimming pools (M marinum), and tap water and occasionally domestic animals (Mycobacterium kansasii). Additionally, rapidly growing NTM such as M abscessus, M chelonae, and M fortuitum have been isolated from soil and natural water supplies.3

Mycobacterium haemophilum is a fastidious organism with a predilection for skin of the chest and extremities. Iatrogenically or inherently immunocompromised patients are most commonly affected6-11; however, there also have been reports in healthy patients.12,13 Infections typically present as painless erythematous papules or nodules that eventually suppurate, ulcerate, and become painful. Presentations involving Fitz-Hugh–Curtis syndrome,13 new B-cell lymphoma,10 and lymphadenitis12 also have been described. Beyond cutaneous involvement, M haemophilum has been cultured from bone, the synovium, the lungs, and the central nervous system.4,9 The majority of morbidities occur in patients with lung involvement.4 Therefore, even patients presenting with isolated cutaneous disease require close follow-up.

Mycobacterium haemophilum is a slowly proliferating organism that is unable to grow in standard egg-potato (Lowenstein-Jensen) medium or agar base (Middlebrook 7H10 or 7H11 agar) without iron supplementation (ferric ammonium citrate, hemin, or hemoglobin). It also requires temperatures of 30°C to 32°C for growth. Its iron requisite is unique, but species such as M marinum and Mycobacterium ulcerans also share reduced temperature requirements. Without a high index of suspicion, growth often is absent because standard Mycobacterium culture techniques will not foster organism growth. Our case demonstrated that special culture instructions must be relayed to the laboratory, even in the face of positive AFB smears. Failure to request hemin and modified incubation temperatures may have contributed to the negative AFB blood culture in our patient.

Due to the relatively rare incidence of M haemophilum infection, there are no known randomized controlled trials guiding antibiotic regimens. Infectious disease specialists often treat empirically with triple-drug therapy derived from locally reported species susceptibilities. The largest case series to date did not identify resistance to amikacin, ciprofloxacin, or clarithromycin.4 Our case identified a novel finding of ciprofloxacin and rifampin resistance, which may highlight the emergence of a newly resistant strain of M haemophilum. Of note, one case of rifampin resistance has been reported, but the culture was drawn from a postmortem specimen in the setting of previously rifampin-sensitive isolates.4 Empiric therapies should be guided by hospital susceptibility reports and expert consultation.

Coinfection with 2 or more NTM—including M tuberculosis, M leprae, and M fortuitum—has been reported.8,14 Temporally distinct coinfections with M leprae and M haemophilum also have been described.15 Thus, practitioners should have a low threshold for repeat cultures in the context of new cutaneous nodules or granulomas, not only to detect concomitant infections but also to identify resistance patterns that might explain recurrent or recalcitrant disease. Immune reconstitution inflammatory syndrome also must be considered with new or worsening lesions, especially in the first months of therapy, as this is a common occurrence when immunosuppressive regimens are tapered to help manage infections.

In conclusion, M haemophilum is an underrecognized infection that presents as cutaneous nodules or lymphadenitis in immunocompromised or healthy individuals. Diagnosis requires a high index of suspicion because its unique growth requirements necessitate special laboratory techniques. Our case represents a classic presentation of this NTM infection in a patient with AML following allogenic stem cell transplantation. Repeat cultures, workup of potentially disseminated infections, and close follow-up are requisite to minimizing morbidity and mortality. A multidisciplinary approach involving infectious disease, medical oncology, radiology, and dermatology best manages this type of infection.

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