Recent increase in non-tuberculous mycobacterial infection in patients with connective tissue diseases in Japan

Non-tuberculous mycobacterial (NTM) infection is currently a growing health concern due to the increasing incidence and the need for prolonged therapy. In patients with connective tissue diseases, use of immunosuppressants may lead to an increased risk of NTM infection. However, few studies have examined the recent incidence of NTM infection among connective tissue diseases patients. This study investigated recent trends in NTM infection among connective tissue diseases patients.

We included adult patients from whose cultures NTM were isolated between January 2009 and October 2017 in our hospital. By reviewing their medical records, connective tissue diseases patients were identified. Types of connective tissue disease, NTM species, and treatment of NTM infection were extracted.

NTM was isolated from 657 patients during the period. Among these, 24 patients had connective tissue diseases. The number and rate of NTM isolates from connective tissue diseases patients increased during the period, with 4 patients 2009 to 2012 (1.9%), and 20 patients from 2013 to 2017 (3.3%; P = 0.04). The proportion of Mycobacterium avium complex (MAC) to total NTM tended to be lower among connective tissue diseases patients (58.3%) than among non-connective tissue disease-patients (72.8%), but the difference was not significant (P = 0.20). Mycobacterium xenopi was significantly more frequent in connective tissue disease patients than in non-connective tissue diseases patients (P < 0.01).

The recent increase in the incidence of NTM infections in connective tissue diseases patients was larger than that in the total population. NTM species other than MAC were isolated from connective tissue diseases patients.