Presumed tuberculous sclerokeratitis in a young immunocompetent female – A rare case and review of literature

INTRODUCTION

Scleritis is a chronic, painful, destructive inflammation of the sclera, which can be anterior or posterior.^[1] Sclerokeratitis is a rare presentation of ocular tuberculosis. It is important to rule out infectious and immune-mediated etiologies of scleritis, which can present with a similar clinical picture, as the treatment modality differs in both. There is a paucity of literature on the same. In this study, we report the diagnostic dilemmas and management of a case of sclerokeratitis secondary to presumed tuberculosis and analyze the available literature relevant to this presentation.

CASE REPORT

A 26-year-old female presented with complaints of pain and redness in the right eye for 2 months. The pain was a dull, boring type radiating to the right temple. She gave no history of cough, fever, joint pain, dry mouth, or loss of appetite/weight. She was fully immunized with no contact history of tuberculosis. She had been diagnosed with episcleritis and treated with topical loteprednol for 1 month with no improvement.

On examination, she was thinly built with stable vitals. Uncorrected visual acuity was 6/6 in both eyes. Slit-lamp examination of the right eye revealed a bluish discoloration of the superior sclera encompassing 2 o’clock hours, associated with swelling and congestion of deep episcleral vessels inferiorly and nasally [Figure 1]. Corneal involvement manifested as ill-defined peripheral stromal opacities adjacent to the area of scleritis with intact corneal sensation. There was no sign of any anterior chamber reaction. The left eye was normal. Pupillary reflex was normal. Intraocular pressure measured using non-contact tonometry was 12 mmHg in both eyes. Dilated fundus examination was normal in both eyes [Figure 2]. B-scan ultrasonography of the right eye showed no signs of posterior scleritis. A provisional diagnosis of anterior nodular scleritis with sclerosing keratitis was made, and treatment was initiated with topical prednisolone 1% and lubricants.

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Figure 1:

Slit lamp photograph of right eye showing anterior nodular scleritis associated with adjacent peripheral corneal stromal opacities.

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Figure 2:

(a and b) Fundus photograph of both eyes showing a normal disc and macula.

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Investigations to determine autoimmune or infectious causes of scleritis were done. Routine hemogram, C-reactive protein, liver, and renal function tests were within normal limits. Erythrocyte sedimentation rate was raised to 96. Anti-streptolysin O, antinuclear antibody, antineutrophil cytoplasmic antibody, and rheumatoid factor tests were normal. Serology for venereal disease research laboratory and human immunodeficiency virus was negative. However, a tuberculin skin test (TST) showed an induration of 20 × 24 mm. Systemic tuberculosis was excluded clinically. Chest radiography and abdomen ultrasonography were normal [Figure 3]. She was advised high-resolution computed tomography – thorax and QuantiFERON-TB gold test, which she could not afford.

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Figure 3:

Chest X-ray (posteroanterior view) of the patient is normal and shows no evidence of any pathological changes.

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The patient was started on anti-tubercular therapy (ATT) for a 4–7 month duration after consultation with the pulmonologist. Intensive therapy included isoniazid 5 mg/kg, rifampicin 10 mg/kg, pyrazinamide 20 mg/kg, and ethambutol 15 mg/kg for 2 months. The patient showed a dramatic clinical response at 4 weeks of follow-up. On slit-lamp examination, swelling and deep episcleral congestion had decreased, and the scleral patch with corneal opacification in the right eye had reduced in size [Figure 4a]. After 2 months, she was put on maintenance therapy with rifampicin 10 mg/kg and isoniazid 5 mg/kg. She is asymptomatic on a 6-month follow-up [Figure 4b and c].

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Figure 4:

(a) Slitlamp photograph of right eye showing signs of resolution of sclerokeratitis four weeks after anti-tubercular therapy(ATT) (arrow), (b and c) After six months of ATT, the right eye shows resolution of scleritis with no hyperemia and a decrease in size of the scleral patch with presence of superior scleral opacity (arrow).

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DISCUSSION

Infectious scleritis is a rare cause of scleritis, accounting for 5–10% of the cases.^[2] In a recent retrospective study analyzing 500 cases of scleritis, tuberculosis was the causative agent in 10.6% of cases of infectious scleritis.^[3] It may occur by direct invasion of the eye by Mycobacterium tuberculosis (MTB), or by a hypersensitivity reaction to circulating MTB antigens.^[4]

Anterior nodular scleritis is the most common presentation of tuberculous scleritis (TS).^[4] Types of peripheral corneal involvement associated with scleritis include peripheral corneal thinning, stromal keratitis, and peripheral ulcerative keratitis.^[5-7] Literature search on TS and keratitis/uveitis in PubMed and Google Scholar showed different clinical presentations, as outlined in Table 1.^[5,8-15] Damodaran et al. and Biswas et al. both reported cases of TS that were severe and showed rapid progression to necrotization and panophthalmitis, necessitating enucleation of the involved eye.^[8,9] Parchand et al. reported a case of diffuse scleritis with two pus points suggestive of scleral abscess, along with choroidal detachment.^[5] Other studies described milder forms of scleritis with or without keratitis or uveitis with a female predominance.

The definitive diagnosis of TS depends on the demonstration of causative bacilli in ocular samples. This includes the growth of the organism in culture media, provision of histopathological evidence, or demonstration of the genome through polymerase chain reaction (PCR).^[16] However, collecting adequate and appropriate samples from ocular structures are difficult. In addition, there is a lack of standardization of primers and considerable variations in the technique of PCR between centers.^[17] Demonstration of acid-fast bacilli in smears is an alternative method of providing direct evidence; however, at least 10⁶ organisms/mL should be present in fluid or tissue.^[17] As ocular tuberculosis is paucibacillary, this translates to an insufficient yield of the organism, making direct microscopy of smears unhelpful for diagnosis, and poses a challenge, as seen in our case.

Treatment for TS is similar to that for pulmonary tuberculosis. The Centers for Disease Control recommends the use of isoniazid, rifampicin, pyrazinamide, and ethambutol for an intensive phase of 2 months, followed by the maintenance phase, for the next 4–7 months, depending on the patient’s response.^[18] The need for topical or systemic corticosteroids in conjunction with ATT in TS is debatable. Sloughy et al. reported that the use of ATT can lead to rapid resolution of inflammation, without the use of corticosteroids.^[11] Lhaj et al. noted that giving a low-dose corticosteroid in conjunction with ATT in latent tuberculosis had a protective effect against tissue damage due to delayed hypersensitivity.^[12] Treatment for TS can be initiated based on the relevant clinical findings, a TST induration of 15 mm or more, a positive response to ATT, and the exclusion of other causes of scleritis.^[19] In our case, based on clinical features, positive TST (> 15 mm), and the endemic area, ATT was started without delay, with a significant outcome.

CONCLUSION

To conclude, anterior nodular non-necrotizing sclerokeratitis is a rare presentation of ocular tuberculosis. A high level of suspicion is needed for diagnosis. Timely intervention with ATT is the key to success.