Ocular tuberculosis presents a diagnostic challenge

By Joanna Lyford, Senior medwireNews Reporter

Mycobacterial ocular inflammation typically arises without concomitant systemic or pulmonary disease and should be suspected in patients who do not respond to anti-inflammatory therapy.

The recommendations come from a study by US researchers, who note that delays in initiating antimicrobial therapy are associated with increased morbidity.

The team led by Debra Goldstein (University of Illinois at Chicago) analyzed presentations and outcomes of 17 patients (26 affected eyes) with suspected ocular mycobacterial disease who were treated at a university-based uveitis clinic between 1995 and 2010.

In all, 14 patients were diagnosed with ocular tuberculosis while three had nontuberculous mycobacterial infection. The average age at presentation was 47.1 years, 11 patients were female, eight were born in the USA, and 12 patients had possible exposure to tuberculosis. Of the 26 affected eyes, four had scleritis, two had granulomatous anterior uveitis, 11 had posterior uveitis, and nine had panuveitis.

Fifteen patients underwent chest radiography, of whom four (26.7%) tested positive for tuberculous disease, while nine had chest computed tomography (CT) imaging, of whom five (55.6%) tested positive. Thus, overall, chest imaging demonstrated granulomatous disease in just 46.7% of patients.

There was a remarkably long delay in diagnosing and treating the condition, Goldstein et al report in JAMA Ophthalmology. Patients were referred to the uveitis clinic by the treating ophthalmologist on average 755.3 days after the onset of ocular symptoms, while antimyocobacterial therapy was initiated 802.3 days after symptom onset.

Race was associated with a delay in referral to the uveitis clinic, with Asian patients being referred much more rapidly than non-Hispanic patients. Posterior uveitis was also associated with longer delays in referral, as was a negative CT result.

Infection resulted in irreversible vision loss (best-corrected visual acuity 20/200 or less) in 10 eyes (38.5%) of eight patients (47.1%). Importantly, patients whose disease was controlled with antimyocobacterial therapy were less likely to have profound vision loss than patients with uncontrolled disease.

Additionally, patients diagnosed and treated more than 500 days after symptom onset were 20 times as likely to have vision loss as were those diagnosed earlier. Age greater than 50 years also correlated with worse outcomes.

Ten eyes (38.5%) of six patients (35.3%) had a relapsing disease course; relapse was more common in patients who had not completed a course of therapy and in those with posterior uveitis.

Goldstein's team concludes: "This study does suggest that tuberculosis must be considered in the differential diagnosis of ocular inflammation, irrespective of patient ethnicity, country of origin, or results of chest imaging; that longer periods of multidrug therapy may be required to control ocular mycobacterial infection; that systemic corticosteroids be used judiciously; and that a reduction in the delay in diagnosis could improve clinical outcomes."

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