Peer Reviewed

Bacterial Infection

Ocular Tuberculosis in a Health Care Worker

Volume 61 - Issue 11 - November 2021

AUTHORS:
Joel Matthews, BS1 • Veneetha Cherian, MD2 • Lynnette Mazur, MD, MPH3

AFFILIATIONS:
1University of Central Lancashire, Preston, United Kingdom 
2Neurology Care Line, Michael E DeBakey VAMC, Houston, Texas
3McGovern Medical School at UT Health, Houston, Texas

CITATION:
Matthews J, Cherian V, Mazur L. Ocular tuberculosis in a health care worker. Consultant. 2021;61(11):e32-e36. doi:10.25270/con.2021.02.00012

Received August 21, 2020. Accepted November 16, 2020. Published online February 23, 2021.

DISCLOSURES:
The authors report no relevant financial relationships.

CORRESPONDENCE:
Lynnette Mazur, MD, MPH, McGovern Medical School at UT Health, 6431 Fannin Street, Houston, Texas 77030 (Lynnette.j.mazur@uth.tmc.edu)

 

A 49-year-old health care worker who emigrated from India 20 years ago presented to our optometry clinic for a routine eye evaluation. His corrected visual acuity was 20/20. His color vision and confrontational visual fields were normal. Funduscopic examination revealed an isolated posterior choroidal granuloma measuring one-disc in diameter in the inferior perifoveal region of the right eye (Figure 1).

Figure 1 fundus view

Figure 1. Fundus view in the right eye at time of diagnosis.

History. The patient’s medical history included Bacillus Calmette–Guérin (BCG) vaccination during childhood, a tuberculin skin test (TST) measuring 23 mm at age 40 years, and a positive QuantiFERON-TB Gold Plus blood test at age 47 years. Findings from all serial chest radiographs conducted from age 40 to 47 years were normal. No further investigations were performed, and no treatment was indicated.

One year prior to his presentation at our clinic, episcleritis was present in the same eye, which spontaneously resolved after 2 weeks. The patient was employed in a local hospital and occasionally worked in a correctional facility. He had no tuberculosis (TB) contacts or family history of TB.

Diagnostic tests. Repeat QuantiFERON-TB Gold Plus and T-SPOT.TB blood tests were both positive. Additional testing included optical coherence tomography (OCT), a noninvasive imaging that uses light waves to take cross-sectional pictures and measure individual retinal layers. Results showed normal macula bilaterally, but an abnormal rounded choroidal excavation at the area of the lesion (Figures 2 and 3).

 

Figure 2 normal OCT

Figure 2. Normal OCT of the disc and macula regions were seen in both eyes, right (top) and left (bottom).

Figure 3 OCT scan of the lesion

Figure 3. OCT scan at the location of the lesion.

The differential diagnosis included congenital, infectious, and neoplastic etiologies (Table 1). Screening for additional extrapulmonary sites included computed tomography (CT) scans of the abdomen, pelvis, and chest. All screens were normal, and magnetic resonance imaging (MRI) of the brain was normal. The consensus from several ophthalmologists and retinal specialists was ocular TB.

Table 1

Treatment and management. As the lesion was near the macula and any progression could adversely affect the patient’s vision, directly observed therapy with 4 drug regimens was prescribed. He started RIPE (rifampicin [RIF], isoniazid [INH], pyrazinamide [PZA], and ethambutol [EMB]) therapy (Table 2). Pyrazinamide was discontinued after the recommended 2 months and the remaining medications were continued for 4 more months. Follow-up examinations at 3 months and 1 year revealed healing at the active edge (Figures 4 and 5).

Figure 4 fundus view

Figure 4. Fundus view of the right eye after 3 months of treatment.

Figure 5 fundus view

Figure 5. Fundus view of the right eye after 12 months of treatment..

Table 2

 

Discussion. TB is caused by the bacterium Mycobacterium tuberculosis and primarily affects the lungs,1 but the brain, eye, kidney, or spine can also be affected. It exists in latent and active forms.2 While about 30% of the world’s population is asymptomatic with latent TB infection (LTBI), only 5% to 10% develop active disease.4,5 This usually occurs within the first 2 years after conversion.2 Persons with LTBI carry live but inactive bacteria and are unable to spread TB to others. Their blood tests and TSTs are usually positive.2 In 2019, the Centers for Disease Control and Prevention (CDC) reported an estimated 13 million persons with LTBI and 8916 cases of active disease in the United States.11

Extrapulmonary disease can occur in any organ. While TB affects the lungs in 80% of patients, 20% have extrapulmonary disease.4 About 60% of patients with extrapulmonary TB do not have pulmonary disease.4 Both primary and secondary ocular TB disease can occur. Primary infection results from direct inoculation and presents with conjunctivitis, keratitis, or episcleritis, while secondary infection results from hematogenous spread from another site and manifests uveal tract, retinal, or optic nerve infection.4 Choroidal tubercles appear as gray, white, or yellow and may be one of the earliest manifestations of disseminated disease.10 Further, single serpiginous lesions appear plaque-like, often with an active edge.10 Ocular involvement is typically disseminated or characterized by multiple lesions but may, as in our patient, present as a single isolated lesion.5 

The diagnosis of ocular TB remains a presumptive clinical diagnosis. Gold standard tests are often not useful, since TB cultures require weeks to process and have low yield from ocular samples. However, the diagnosis is supported by positive TST or interferon-gamma release assays.6

According to current CDC guidelines for LTBI,7 our patient was in a high-priority group for treatment (Table 3). He had a positive TB blood test, had a TST measurement of 10 mm or more, was an immigrant from Asia, and had worked in a correctional facility.7 However, our patient did not fit earlier guideline recommendations.8

Table 3

 

The principles underlying the treatment of pulmonary TB also apply to extrapulmonary disease.9 The preferred regimen for treating adults with TB caused by organisms that are not known or suspected to be drug resistant is a regimen consisting of an intensive phase of at least 2 months of INH, RIF, PZA, and EMB followed by at least 4 months of INH and RIF.9

Conclusions. This case underpins the difficulty in the diagnosis of ocular TB and the importance of surveillance and screening for occult asymptomatic tuberculous foci in high-risk patient populations. Differentiating between LTBI from active disease is important for preventing drug-resistant TB development.

References

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