Uveitis—The Tortured Tale of the Tubercle

Abstract

Tuberculous uveitis has been recognized for a long time (Antoine Maitre-Jan described the first case of iritis associated with tuberculosis [TB] in 1707), and much is understood about its mechanisms. Numerous pathology studies have demonstrated ocular presence of Mycobacterium tuberculosis in cases of uveitis;animal studies have demonstrated that intraocular or miliary M tuberculosis infection will cause uveitic disease. The range of uveitis associated with TB is broad and includes anterior, intermediate, posterior, and panuveitis (including some interesting variants such as serpiginoid uveitis, retinal vasculitis, and choroidal tubercles). While most patients with biopsy-proven tubercular uveitis will have positive tuberculin test results (either the tuberculin skin test or the more recent interferon γ release assays [IGRA] such as QuantiFERON Gold), most patients with tubercular uveitis will have no evidence of pulmonary or other systemic disease. Multidrug treatment of true tubercular uveitis (often with concomitant corticosteroids) will often definitively resolve the uveitis. Conversely, many patients with uveitis will have positive tuberculin test results, particularly in endemic areas: do these patients actually have tubercular uveitis, or do they have 2 independent conditions? Despite near-consensus agreement among experts on these facts, tubercular uveitis remains very challenging to the practicing uveitis specialist. In 2015, the Uveitis Specialists Study Group surveyed the members of the American Uveitis Society, presenting 2 case scenarios and asking members for their estimation of the likelihood of tuberculous uveitis, their preferred workup, and recommended treatment. 1 The group found essentially no consensus among uveitis specialists with respect to any of these questions, with likelihood estimates for a single case ranging from 0% to 90%, and approximately equal numbers of respondents recommending treatment of 6, 9, and 12 months for TB in likely cases. Later, a second group of primarily non-US-based physicians was given the same set of scenarios. Their assessments, workup, and suggested treatments were also highly variable and in many cases significantly different from those of US-based specialists. 2 This difficulty arises from the lack of a gold standard diagnostic test for tubercular uveitis. It is believed that much of the uveitis associated with tuberculosis is caused by innate and adaptive immune responses to tubercular antigens as much as to the organism itself. As such, very small bacterial loads, perhaps as low as a single bacillus, 3 can induce substantial inflammation. While the polymerase chain reaction has been successfully used in many cases to diagnose tubercular uveitis, its false-negative rate is unknown; a negative result does not rule out tubercular disease. In the absence of a definitive laboratory test, the presence of a compatible form of uveitis and a positive skin or IGRA test result is taken as presumptive diagnosis for tubercular uveitis.

An excursion into ocular tuberculosis

“…Phenotypes that increase the risk of treatment failure include vitreous haze, snow banking, and choroidal involvement;[ 4 ] conversely, features associated with successful treatment include monocular involvement, posterior uveitis, normal chest X-ray, and the absence of vitreous haze. [ 59 ]…”

Tubercular Retinal Vasculitis: Diagnostic Dilemma and Management Strategies

“…15 , 17 , 34–37 Tractional and combined-mechanism detachments are the most complex surgical indications in retinal vasculitis, which may limit the functional gains in spite of good anatomical outcomes. 34 , 35 Vitrectomy even in the absence of tractional detachment could be complicated by tightly adherent peripheral membranes with thin ischemic underlying retina, vitreoschisis, and difficult induction of posterior vitreous detachment. 34 In young patients with clear lens, an encircling belt buckle might help as peripheral membranes could be difficult to access.…”

“…34 In young patients with clear lens, an encircling belt buckle might help as peripheral membranes could be difficult to access. 34 , 35 Vitrectomy can also help in faster resolution of uveitis by the removal of inflammatory debris from the vitreous. 36 It could also be a diagnostic aid in patients with inconclusive TST/QFT and chest radiography by providing a vitreous sample for molecular diagnosis (PCR).…”

“…15,29 Vitrectomy is indicated in tubercular or other occlusive vasculitis for visually significant epiretinal membrane or vitreomacular traction, non-clearing vitreous hemorrhage, persistent vitritis despite medical management, progressive tractional retinal detachment and finally for diagnostic biopsy in intractable cases. 15,17,[34][35][36][37] Tractional and combined-mechanism detachments are the most complex surgical indications in retinal vasculitis, which may limit the Figure 4 Fluorescein angiography showing inactive TRV. Like Figure 3 (not the same eye), this angiogram shows peripheral capillary non-perfusion in the left upper corner; the blocked fluorescence along the proximal edge of non-perfusion is due to blot hemorrhages and appears darker.…”