Pulmonary disease caused by M. malmoense in HIV negative patients: 5-yr follow-up of patients receiving standardised treatment.
The literature concerning the management of pulmonary disease caused by Mycobacterium malmoense consists of retrospective reports on small series of patients. A recent multicentre trial conducted by the British Thoracic Society provided an opportunity to prospectively document the clinical features and response to treatment of this relatively rare but challenging disease in a substantial number of patients. When two positive cultures were confirmed by the Mycobacterium Reference Units for England, Wales, Scotland or Scandinavia, the coordinating physician invited the patient's physician to enrol the patient, who was then treated on a random basis with either rifampicin plus ethambutol or rifampicin, ethambutol and isoniazid for 2 yrs. Clinical, bacteriological and radiological progress were monitored at set intervals for 5 yrs. In over 5 yrs a total of 106 patients were recruited to the study. The mean age was 58 yrs, range 24-89 A total of 58% were male and just over half previously or at the time ofthe study had other lung diseases. Sputum was positive on direct smear in 58%. Cavitation was seen on the chest radiographs of 74%, the majority having cavities of > or = 2 cm in diameter. Less than half of the patients showed bilateral disease, 26% having involvement of more than three lung zones. Disease was confined to the upper zone(s) in 30%. Other lung diseases were evident in 52%. Although clinical response was judged satisfactory at most reviews (90%), one in three patients died within 5 yrs and <5% were thought to have died primarily because of M. malmoense. There were three failures of treatment and eight relapses after the end of treatment. There was no correlation between failure of treatment/relapse and in vitro resistance. A total of 63 (59%) of patients were alive at 5 yrs, of whom 44 (42% of the total entry) were known to be cured. Pulmonary disease caused by Mycobacterium malmoense is a serious condition that is associated with high morbidity and mortality. The results of standard susceptibility tests do not correlate with the bacteriological response of the disease to chemotherapy. Rifampicin and ethambutol, with or without isoniazid, cured only 42% of patients but were better tolerated than previously described, more complex regimens of equal or lesser efficacy. There is a need for more effective regimens that will reduce mortality and failure of treatment/relapse rates, but, in addition, attention should be directed at improving management of comorbid conditions and improving the general health of the patient.