Positive interferon‐gamma release assay (IGRA) test in a case of non‐tuberculous mycobacterium associated uveitis

Abstract

AbstractPurpose It is not always known that Interferon‐gamma release assay (IGRA) tests can also react with some non‐tuberculous atypical strains of mycobacteria (NTM). The aim of this work was to review the cross‐reactivity of IGRA tests and its consequences in a case of with a positive IGRA test associated with of a non‐tuberculous mycobacterium (M. kansasii).Methods Report of a 66 year old male uveitis patient with cystoid macular oedema and occult bilateral indocyanine green angiography‐detected choroiditis resistant to inflammation suppressive therapy. A QuantiFERON®‐TB Gold test was positive indicating exposure to the Mycobacterium tuberculosis complex. Before starting antibiotic treatment cultures from bronchial aspirates was performed yielding the agent Mycobacterium kansasii. A review of cross‐reactivity of IGRA tests with non‐tuberculous atypical mycobacteria was performed.Results Drug‐sensitivity of Mycobacterium kansasii was found to be equal to Mycobacterium tuberculosis although a longer duration of therapy is recommended. The patient was treated with anti‐tuberculous drugs for 18 months. Uveitis responded to treatment within three months. A review showed that there are at least 7 NTM strains that cross‐react with IGRA tests some of which do not respond to classical anti‐tuberculous therapy.Conclusion A positive IGRA test is a support for diagnosing tuberculous uveitis. However, these tests cross‐react with NTM atypical strains, some of which do not respond to classical anti‐tubercultuberculous therapy with deleterious consequences if an adequate therapy is not given.