Relapsing anterior nodular sclerokeratitis as the initial presentation of a latent tuberculosis: a case report

¹Department of Ophthalmology, Military Hospital of Tunis, Tunis El Manar University, Tunis, Tunisia

^&Corresponding author
Rahma Saidane, Department of Ophthalmology, Military Hospital of Tunis, Tunis El Manar University, Tunis, Tunisia

Introduction    

Tuberculosis is a systemic infectious disease caused by Mycobacterium tuberculosis, which transmitted from human-to-human and is mainly spread by airborne [1]. It is the main infectious cause of morbi-mortality in developing countries where it is endemic. A significant resurgence of this condition in developed countries has been recorded due to the increase of human immunodeficiency virus infection [2]. Tuberculosis mainly affects the lungs. However, ocular involvement is not uncommon [2]. This is most often manifested by posterior uveitis. Other, rarer and nonspecific ocular manifestations can produce various clinical presentations. In the absence of general manifestations, the diagnosis of ocular involvement is difficult and challenging, explaining partially the therapeutic delay [3]. We report a challenging case of a Tunisian patient who had a long history of unilateral recurrent sclerokeratitis without systemic symptoms. The patient was diagnosed with presumed ocular tuberculosis and responded to antitubercular therapy (ATT) administrated after exclusion of other aetiologies.

Patient and observation     

Patient information: a 42-year-old man, presented with severe recurrent ocular pain, redness, and photophobia of his right eye for several days. He had a history of multiple episodes of scleritis occurring in the same eye over the last two years, with a poor response to topical steroids and oral non-steroidal and steroidal anti-inflammatory drugs. The patient was referred to our department and hospitalized for etiologic inquiry. There was no history of loss of appetite/weight, joint pains, dryness of mouth, cough, expectoration, or fever. There was no relevant contact history with a tuberculosis case.

Clinical findings: on examination, best corrected visual acuities were 20/20 in both eyes (Snellen chart). Lids and adnexa were normal. Slit-lamp examination of the right eye showed marked diffuse sclero-conjunctival congestion in the temporal side from 7-11 o'clock position, centered by two yellowish scleral nodules with circum-corneal stromal infiltration. Episcleral and scleral vessels were engorged (Figure 1). No abnormality was noted in the iris and the anterior chamber examination. Intraocular pressure was 16 mmHg. Fundus evaluation under mydriasis was unremarkable. The left eye examination was normal.

Diagnostic assessment: ultrasound B scan demonstrated no signs of posterior scleritis (Figure 2). Fluorescein angiography showed no evidence of papillitis, vitreous condensations, vasculitis, or any subretinal nodules suggestive of granulomas, with normal appearance of the macula (Figure 3). Systemic physical examination including respiratory system was normal. Laboratory work up (hematocrit, hemoglobin, white blood cell counts, platelets and erythrocyte sedimentation rate, C-reactive protein, angiotensin-converting enzyme) was unremarkable. Serology for syphilis, viral hepatitis (B and C) and human immunodeficiency virus (1-2), antinuclear antibody, rheumatoid factor, cytoplasmic, and perinuclear antineutrophil cytoplasmic antibodies were all negative. The tuberculin skin test (TST) results showed a 15 mm induration and the QuantiFERON-TB Gold test was positive with value over 3 IU/ml. Sputum smears for acid-fast bacilli were negative. Thoraco-abdominopelvic CT examination revealed no abnormalities. The diagnosis of presumed tuberculous anterior nodular sclerokeratitis was made based on clinical findings, positive TST of 15 mm, positive QuantiFERON-TB Gold test, exclusion of other aetiologies and especially with the high endemicity of tuberculosis in our country.

Therapeutic intervention: two months of anti-tubercular therapy (ATT) including Isoniazid, Rifampicin, Pyrazinamide, Ethambutol plus four months of Isoniazid and Rifampicin was started. Along with ATT, topical steroid and atropine were also continued.

Follow-up and outcomes: the patient showed spectacular response within few days of starting treatment as the symptoms decreased to minimal. Upon follow-up, nodules started resolving after a month of treatment (Figure 4). Presently, the patient is on regular follow-up with no ocular or systemic complication of ATT.

Informed consent: informed consent was obtained from the patient prior to collecting data and issuing iconography.

Discussion     

Scleritis is a painful inflammatory condition characterized by edema and infiltration of the sclera [4]. The classification of Watson and Hayreh divide scleritis into two major entities anterior and posterior based on the site of inflammation [4]. Anterior scleritis is the most common type, and it is also subdivided into diffuse, nodular and necrotizing [4]. These different forms of anterior scleritis differ in severity and prognosis [4]. Most cases of scleritis are associated to systemic conditions, especially autoimmune disorders. Infectious scleritis is a less common entity and counts for 5-10% of all cases of scleritis [5]. The most commonly associated infection is herpes zoster [4]. Tuberculosis is a relatively uncommon cause of infective scleritis. It has been first described in 1895 in tuberculosis sanatorium [6]. Since that, several cases have been published [7,8]. Involvement of the ocular surface is considered to be an atypical manifestation of ocular tuberculosis. It can take different forms, such as a conjunctival nodule, conjunctival ulcer, phlyctenular keratoconjunctivitis, scleritis, episcleritis and sclerokeratitis [9]. In Tunisia, known as a tuberculosis endemic country, a previous study found that tubercular uveitis accounted for 1.1% of all uveitis cases [9]. The exact frequency of sclerokeratitis is unknown.

Extrapulmonary tuberculosis as ocular tuberculosis may occur in the absence of pulmonary disease. The exact pathogenesis of TB scleritis is still in debate. Two mechanisms have been claimed to be responsible for the development of tuberculosis sclerokeratitis. The first one is linked to the presence of the pathogen intraocularly. This exceptionally reaches the eye by direct inoculation. In most cases, the eye is affected by hematogenous dissemination from distant site such as lungs. The second mechanism involves a hypersensitivity reaction secondary to antigenic release [2]. Faced with this great clinical polymorphism, the lack of specificity and the difficulty of obtaining bacteriological evidence, the diagnosis of ocular tuberculosis remains a real challenge. A classification of the different situations encountered has been proposed in order to harmonize diagnostic and therapeutic management of ocular TB. Two main situations may arise: the diagnosis is certain, in presence of evidence of MT on intraocular samples (by Ziehl-Neelsen staining, PCR or cultures) or the diagnosis is presumptive on a set of clinical, radiological, bacteriological, histological and immunological arguments and in the absence of evidence of TM in the eye. In this case, the diagnosis of ocular TB can only be made posteriorly, when a good response to TAT is obtained with a significant decrease of the ocular inflammation. Sclerokeratitis as a form of ocular TB is treated with medical anti-tuberculosis treatment (ATT) similar to that used for pulmonary TB [10]. The center for disease control (CDC) recommends the use of isoniazid, rifampicin, pyrazinamide, and ethambutol for an initial 2-month period followed by a 4 to 7 months biotherapy regime. A short term corticotherapy given concomitantly with anti-tubercular therapy drugs has not proven any benefic effect [10]. The administration of ATT was associated to less recurrence of ocular inflammation [10].

Conclusion     

Tuberculous sclerokeratitis is a rare form of extrapulmonary TB. It can be the first manifestation of the disease and can remain isolated without any systemic condition. Since ocular tuberculosis can take on different aspects, the problem of differential and positive diagnosis can be a real challenge, in particular in the absence of a non-invasive diagnostic test allowing to provide bacteriological proof of ocular involvement. Therapeutic ATT test are of considerable interest. The visual prognosis depends on the establishment of a suitable treatment, allowing stabilization or clinical improvement.

Competing interests     

The authors declare no competing interests.

Authors' contributions     

All authors contributed to conception, design and revising of the manuscript. All the authors have read and agreed to the final manuscript.

Figures     

Figure 1: right eye photography showed marked diffuse sclero-conjunctival congestion in temporal side from 7-11 o'clock position, centered by two yellowish scleral nodules with circum-corneal stromal infiltration; episcleral and scleral vessels were engorged

Figure 2: (A, B) ultrasound B scan demonstrated no signs of posterior scleritis in both eyes

Figure 3: fundus photography (A) and fluorescein angiography (B) of both eyes showed no evidence of papillitis, vitreous condensations, vasculitis, or any subretinal nodules suggestive of granulomas, with normal appearance of the macula

Figure 4: right eye photography at 4 months of ATT showed complete resolving of the scleral inflammation and a peripheral corneal scar

References