Pathogenesis of ocular tuberculosis: New observations and future directions

Diagnostic Biomarkers for Uveitis: Serum BAFF and CXCL9 in Differentiating Ocular Sarcoidosis, Tuberculosis and Other Entities with Implication for QuantiFERON-Positive Uveitis

PURPOSE

To evaluate serum B cell activating factor (BAFF) and CXCL9 as diagnostic biomarkers for ocular sarcoidosis and ocular tuberculosis (TB). We also explore their role in the stratification of patients with QuantiFERON (QFT)-positive uveitis without another identifiable cause.

METHODS

Eighty uveitis patients with various entities were included: 10 with ocular sarcoidosis, 35 with TB-related uveitis (including 11 confirmed (ocular TB) and 24 QFT-positive uveitis of unknown cause) and 35 with other uveitis entities. Levels of serum BAFF and CXCL9 were measured.

RESULTS

Serum BAFF was higher in ocular sarcoidosis compared to other groups (area under the curve (AUC) = 0.74; 95% CI: 0.53-0.96, p = 0.017). At an optimal serum BAFF cut-off point of 772.3 pg/ml, the sensitivity was 70.0% (95% CI: 39.7-89.2) and the specificity was 89.1% (95% CI: 77.0-95.3). Serum CXCL9 was comparable between ocular sarcoidosis and confirmed ocular TB but was significantly higher in these groups compared to other uveitis entities (AUC = 0.71, 95% CI: 0.57-0.86, p = 0.011). To differentiate ocular sarcoidosis and TB from other uveitis entities, CXCL9 (cutoff: 105.5 pg/ml) showed a sensitivity of 88.9% (95% CI: 67.2-98.0) and a specificity of 54.3% (95% CI: 38.2-69.5). High CXCL9 TB-related uveitis patients demonstrated a higher proportion of uveitis resolution when fully treated with antitubercular treatment (ATT) (p = 0.027).

CONCLUSIONS

Serum BAFF and CXCL9 serve as potential diagnostic biomarkers for differentiating ocular sarcoidosis, ocular TB and other uveitis entities. These might identify QFT-positive uveitis who are most in need of ATT.

Rare bilateral corneoscleral perforation secondary to ocular tuberculosis: a case report and clinical insights

BACKGROUND

This case represents a rare presentation of bilateral corneoscleral perforation secondary to presumed ocular mycobacterium tuberculosis infection with the goal of reporting a case of bilateral corneoscleral perforation in the setting of a positive interferon-γ release assay (IGRA) test.

FINDINGS

A 27-year-old patient presented with five months of redness, worsening eye pain, and five days of decreasing vision. Visual acuity (VA) was counting fingers bilaterally. Intraocular pressure (IOP) was 10 mmHg and 19 mmHg in the right and left eye, respectively. A slit lamp examination disclosed conjunctival injection, corneal haze, bilateral mutton-fat keratic precipitates, and a hypopyon in both eyes. The right eye had a 1.5 mm × 1.5 mm Seidel-positive corneal perforation with uveal prolapse. Similarly, the left eye had a 0.5 mm × 0.5 mm Seidel-negative inferior corneal perforation with uveal plugging. The chest X-ray showed a left-sided pleural effusion.

CONCLUSION

Computed tomography (CT) of the face and sinuses showed bilateral circumferential globe thickening. IGRA was positive. All other rheumatologic and infectious workups were negative, including HIV, ACE, ANA, ANCA, CRP, anti-scleroderma antibody and HCV. The patient was treated with intravenous methylprednisolone and seven months of rifampin, isoniazid, pyrazinamide, and ethambutol. This workup shows the rare bilateral corneal involvement of ocular tuberculosis.

Detection of Mycobacterium tuberculosis DNA in intraocular fluid of 11 suspected tuberculous uveitis patients by multiplex PCR

BACKGROUND

This study aims to detect Mycobacterium tuberculosis complex (MTBC) DNA in intraocular fluid from clinically suspected tuberculous uveitis patients using multiplex polymerase chain reaction (PCR) and investigate the diagnostic utility of multiplex PCR for tuberculous uveitis.

METHODS

Primers targeting three specific genes (MPB64, CYP141, and IS6110) within the MTBC genome were designed. Multiplex PCR was conducted using DNA from the H37Rv strain as well as DNA extracted from fluids of confirmed tuberculosis patients to assess primer specificity and method feasibility. Intraocular fluid samples were collected during the initial visit for multiplex PCR detection of MTBC DNA. The results of multiplex PCR tests were correlated with intraocular fluid findings and clinical profiles of patients clinically diagnosed with tuberculous uveitis who underwent standard antituberculosis therapy.

RESULTS

Multiplex PCR was employed to detect MTBC DNA in intraocular fluid samples from 15 patients clinically suspected of having tuberculous uveitis, with no amplification bands observed in the DNA lanes for the three target genes. T-cell spot test (T-SPOT) results were positive in 11 patients (100%), while purified protein derivative (PPD) tests were positive in 5 patients (45.5%). Abnormal chest CT findings were noted in 4 patients (36.4%), including one case of active pulmonary tuberculosis and three cases of inactive pulmonary tuberculosis. Retinal vasculitis was observed in 6 eyes (46.2%), panuveitis in 5 eyes (38.5%), and intermediate uveitis in 2 eyes (15.4%). The average duration of antituberculosis therapy administered to the 11 patients was 7.1 months (range: 6-10 months). The medium LogMAR Best Corrected Visual Acuity (BCVA) significantly improved at the last follow-up (Z=-2.371, P = 0.018).

CONCLUSIONS

Standard antituberculosis therapy demonstrated effectiveness in treating 11 patients clinically suspected of having tuberculous uveitis despite the absence of detectable MTBC DNA in intraocular fluid via multiplex PCR. Further investigation is warranted to elucidate the role of PCR in diagnosing ocular tuberculosis among Chinese individuals.

Management of Tubercular Retinal Vasculitis: A Case Report From an Endemic Region

India, being an endemic country for tuberculosis, has a very high prevalence of pulmonary and extrapulmonary tuberculosis. Various manifestations of ocular tuberculosis have been described, including granulomatous anterior uveitis, serpiginous choroiditis, and retinal vasculitis. We hereby describe the case of a 39-year-old male patient who presented to our clinic with complaints of diminished vision in the right eye for five months. His best-corrected visual acuity was 6/12 in the right eye with normal anterior segment examination. He was misdiagnosed as having central serous chorioretinopathy in the right eye at a primary center. The patient had typical fundus findings of perivascular infiltrates, focal vascular tortuosity, vitreous snowball infiltrates, and cystoid macular edema. Fluorescein angiography was done to evaluate the retinal findings and capillary non-perfusion areas. The patient was referred to a physician for the initiation of anti-tubercular treatment. Posterior sub-Tenon injection of triamcinolone acetonide was given for cystoid macular edema, and laser photocoagulation of capillary non-perfusion areas of the retina was done. The patient responded well to treatment with resolution of macular edema and healing of perivascular infiltrates. His visual acuity improved to 6/6 at the three-month follow-up. The patient was followed up for a period of two years with no reported complications or recurrences. This case highlights the diagnostic features of tubercular retinal vasculitis and its management.

Ocular Tuberculosis Diagnosis Through Biomarkers: Clinical Relevance of Serum C1q and Whole Blood Interferon Gene Signature Score

PURPOSE

To assess the clinical relevance of pathophysiology-based biomarkers, specifically serum C1q and whole blood interferon gene signature score (IGSS), in ocular tuberculosis (OTB) diagnosis by conducting an integrative analysis of clinical presentations and treatment response.

METHODS

This retrospective cohort study analysed data from 70 patients with suspected OTB at a tertiary care uveitis practice in Indonesia. Serum C1q levels and whole blood IGSS were quantified. Patients were categorized into four quadrants based on their biomarker profiles: quadrant 1 (high C1q & low IGSS), quadrant 2 (high C1q & high IGSS), quadrant 3 (low C1q & high IGSS), and quadrant 4 (low C1q & low IGSS). Characteristics of clinical presentations, work-up results, and treatment outcomes were explored according to the predefined quadrants.

RESULTS

We identified that the majority of OTB patients diagnosed with concurrent active pulmonary TB were in quadrant 1, 2, or 3 (20/23, 87.0%). Twenty-seven patients (27/47, 57.4%) with clinically undifferentiated uveitis were in quadrant 4 (p < 0.001). Among patients in quadrants 1, 2, and 3, completion of a full course of antitubercular treatment (ATT) was associated with a lower number of patients showing persistence or recurrence of ocular inflammation compared to those who were not fully treated with ATT (14.3% vs 85.7%, p = 0.001).

CONCLUSIONS

Based on the analysis of clinical features and treatment outcomes, patients with elevated levels of either or both serum C1q and whole blood IGSS may reflect active TB disease in the eye, necessitating full ATT management.

Diagnosis and treatment of tuberculosis presenting as uveitis based on stochastic simulation in systems biology

Tuberculous uveitis can be a manifestation of extrapulmonary tuberculosis or an allergic reaction to tuberculosis infection. The clinical signs and symptoms of other uveitis causes are generic, making a false diagnosis simple. We present a brief introduction to theoretical modelling and simulation in systems biology and explore the consequences of TB uveitis if left untreated. Patients were admitted to our hospital with recurrent fever. They had a previous definitive diagnosis of binocular uveitis and a positive interferon gamma release assay (IGRA) test result. At the time, there was no antituberculosis medicine available, and immunosuppressive and glucocorticoid therapy did not work. After the admission, their pleural fluid tested positive for Mycobacterium tuberculosis. No other causes to explain the fever were found. A diagnosis of tuberculosis was made, and their body temperature normalized after antituberculosis treatment and closed chest drainage. Vigilance should be exercised to rule out tuberculous uveitis in cases of unexplained uveitis; this calls for IGRA screening, tuberculin skin testing, and cyst imaging. For patients with latent tuberculosis infections, it is recommended to administer antituberculosis treatment, after excluding other possible causes, and to avoid using glucocorticoids in isolation.

Diagnosis and Treatment of Tubercular Uveitis in Taiwan - Consensus of Expert Panels

There is currently a lack of guidelines with regard to tubercular uveitis (TBU) management in Taiwan. We therefore propose an evidence-based consensus on the management for TBU. The Taiwan Ocular Inflammation Society conducted a meeting that included nine ophthalmologist and one infection disease expert that focused on three broad areas of (1) nomenclature for TBU, (2) assessment and diagnosis for TBU, and (3) treatment of TBU. Brief literature review on TBU diagnosis and management was conducted that informed this panel meeting in order to make decisions on each consensus statements. In terms of our results, a consensus statements and recommendations for the diagnosis and management of TBU were developed. This consensus statement provides an algorithmic approach toward diagnosing and managing TBU. These statements are meant to enhance but not replace individual clinician-patient interactions and to facilitate real-world clinical practice improvement in terms of TBU patients care.

Mycobacterium dormancy and antibiotic tolerance within the retinal pigment epithelium of ocular tuberculosis

Tuberculosis (TB) is a leading cause of death among infectious diseases worldwide due to latent TB infection, which is the critical step for the successful pathogenic cycle. In this stage, Mycobacterium tuberculosis resides inside the host in a dormant and antibiotic-tolerant state. Latent TB infection can also lead to multisystemic diseases because M. tuberculosis invades virtually all organs, including ocular tissues. Ocular tuberculosis (OTB) occurs when the dormant bacilli within the ocular tissues reactivate, originally seeded by hematogenous spread from pulmonary TB. Histological evidence suggests that retinal pigment epithelium (RPE) cells play a central role in immune privilege and in protection from antibiotic effects, making them an anatomical niche for invading M. tuberculosis. RPE cells exhibit high tolerance to environmental redox stresses, allowing phagocytosed M. tuberculosis bacilli to maintain viability in a dormant state. However, the microbiological and metabolic mechanisms determining the interaction between the RPE intracellular environment and phagocytosed M. tuberculosis are largely unknown. Here, liquid chromatography-mass spectrometry metabolomics were used to illuminate the metabolic state within RPE cells reprogrammed to harbor dormant M. tuberculosis bacilli and enhance antibiotic tolerance. Timely and accurate diagnosis as well as efficient chemotherapies are crucial in preventing the poor visual outcomes of OTB patients. Unfortunately, the efficacy of current methods is highly limited. Thus, the results will lead to propose a novel therapeutic option to synthetically kill the dormant M. tuberculosis inside the RPE cells by modulating the phenotypic state of M. tuberculosis and laying the foundation for a new, innovative regimen for treating OTB.

IMPORTANCE

Understanding the metabolic environment within the retinal pigment epithelium (RPE) cells altered by infection with Mycobacterium tuberculosis and mycobacterial dormancy is crucial to identify new therapeutic methods to cure ocular tuberculosis. The present study showed that RPE cellular metabolism is altered to foster intracellular M. tuberculosis to enter into the dormant and drug-tolerant state, thereby blunting the efficacy of anti-tuberculosis chemotherapy. RPE cells serve as an anatomical niche as the cells protect invading bacilli from antibiotic treatment. LC-MS metabolomics of RPE cells after co-treatment with H2O2 and M. tuberculosis infection showed that the intracellular environment within RPE cells is enriched with a greater level of oxidative stress. The antibiotic tolerance of intracellular M. tuberculosis within RPE cells can be restored by a metabolic manipulation strategy such as co-treatment of antibiotic with the most downstream glycolysis metabolite, phosphoenolpyruvate.

Clinical Insights: Antimicrobial Therapy for Infectious Uveitis

Infectious uveitis is a major global cause of vision impairment. Despite the eye's immune privilege, afforded by the blood-ocular barrier that restricts microbial entry, several pathogens such as bacteria, viruses, fungi, and parasites can still infiltrate and cause ocular infections and complications. Clinicians often encounter significant challenges in treating infectious uveitis due to limited or ineffective treatment options. Modern molecular techniques and imaging can aid in diagnosing and assessing intraocular infections. Various antimicrobial therapies exist, spanning topical and systemic treatments, but these are constrained by issues like drug concentration, penetration, effective duration, toxicity, and side effects. Treatment approaches also differ based on the infection's etiology. This review provides recent updates on antimicrobial therapies from a clinical perspective, covering topical, systemic, and regional treatments for infectious uveitis.

Mycobacterium dormancy and antibiotic tolerance within the retinal pigment epithelium of ocular tuberculosis

Tuberculosis (TB) is a leading cause of death among infectious diseases worldwide due to latent TB infection, which is the critical step for the successful pathogenic cycle. In this stage, Mycobacterium tuberculosis resides inside the host in a dormant and antibiotic-tolerant state. Latent TB infection can lead to a multisystemic diseases because M. tuberculosis invades virtually all organs, including ocular tissues. Ocular tuberculosis (OTB) occurs when the dormant bacilli within ocular tissues reactivate, originally seeded by hematogenous spread from pulmonary TB. Timely and accurate diagnosis as well as efficient chemotherapies are crucial in preventing poor visual outcomes of OTB patients. Histological evidence suggests that retinal pigment epithelium (RPE) cells play a central role in immune privilege and in the protection from the antibiotic effects, making them an anatomical niche for invading M. tuberculosis . RPE cells exhibit high tolerance to environmental redox stresses, allowing phagocytosed M. tuberculosis bacilli to maintain viability in a dormant state. However, the microbiological and metabolic mechanisms determining the interaction between the RPE intracellular environment and phagocytosed M. tuberculosis are largely unknown. Here, liquid chromatography mass spectrometry (LC-MS) metabolomics was used to illuminate the metabolic state within RPE cells reprogrammed to harbor dormant M. tuberculosis bacilli and enhance the antibiotic tolerance. The results have led to propose a novel therapeutic option to synthetically kill the dormant M. tuberculosis inside the RPE cells by modulating the phenotypic state of M. tuberculosis , thus laying the foundation for a new, innovative regimen for treating OTB.

Importance

Understanding the metabolic environment within the retinal pigment epithelium (RPE) cells altered by infection with M. tuberculosis and mycobacterial dormancy is crucial to identify new therapeutic methods to cure OTB. The present study showed that RPE cellular metabolism is altered to foster intracellular M. tuberculosis to enter into the dormant and drug tolerant state, thereby blunting the efficacy of anti-TB chemotherapy. RPE cells serve as an anatomical niche as the cells protect invading bacilli from antibiotic treatment. LC-MS metabolomics of RPE cells after co-treatment with H2O2 and M. tuberculosis infection showed that intracellular environment within RPE cells is enriched with greater level of oxidative stress. The antibiotic tolerance of intracellular M. tuberculosis within RPE cells can be restored by a metabolic manipulation strategy such as co-treatment of antibiotic with the most downstream glycolysis metabolite, phosphoenolpyruvate.

The Decreased Treg Cells Number Associated with Retinal Lesion Size in Ocular Toxoplasmosis

Introduction

The imbalance of the immune response is an important factor contributing to the incidence of ocular toxoplasmosis (OT). Regulatory T cells (Treg) play a key role in maintaining the balance between Th1 and Th17 immune responses, while interleukin-27 (IL-27) levels are related to the differentiation of Th17 cells. This study analyzes the differences in the number of Treg cells and the level of IL-27 between OT patients and seropositive individuals without ocular lesions and its correlation with retinal lesion size.

Methods

This analytic observational study, conducted for 8 months, involved 11 OT patients and 10 seropositive individuals without ocular lesions. All subjects underwent a comprehensive ophthalmological examination. Retinal lesions were documented by fundus photographs and the size was measured using Digimizer 4.2.2.0 software. Isolation of peripheral blood mononuclear cells (PBMC) was performed to measure the number of Treg cells using flow cytometry and interleukin-27 levels were assessed using the Sandwich enzyme-linked immunosorbent assay (ELISA) technique. Data were analyzed with SPSS.

Result

The number of Treg cells in the OT group (47.16 ± 15.66%) was lower than in the seropositive group without the ocular lesions (62.86 ± 17.08%) (p = 0.029). The serum IL-27 levels in the OT group were not significantly different from the seropositive group without the ocular lesions (p = 0.360). The number of Treg cells was significantly related to retinal lesion size (p = 0.043), with a correlation coefficient of -0.648, indicating a strong and inverse correlation. There was no significant correlation between serum IL-27 levels and retinal lesion size (p = 0.556).

Conclusion

Ocular toxoplasmosis patients have a low number of Treg cells that are inversely related to the retinal lesion size. The size of the retinal lesion increases as the number of Treg cells decreases.

Pathogenesis of Bacterial Uveitis

PURPOSE

To describe the pathogenesis and the general immune mechanisms of the most frequent causes of bacterial uveitis.

METHODOLOGY

Narrative review.

RESULTS

Both extra- and intracellular bacteria can induce uveitis, whereas intracellular bacteria are generally transported into the inner eye via cells of the innate immune system, mainly macrophages. Systemic adaptive immunity is usually induced before the bacteria are localized to the inner eye, and once T and B cells have detected the pathogens behind the blood-eye barriers they elicit an acute and/or chronic inflammatory response deteriorating visual acuity that can severely affect the non-regenerating, intraocular tissues.

CONCLUSIONS

An understanding of pathogenic mechanisms, and its correlation with clinical and imaging features, can facilitate early recognition of microbial factors and institution of appropriate therapy.

The immune response in tubercular uveitis and its implications for treatment: From anti-tubercular treatment to host-directed therapies

Tubercular uveitis (TB-uveitis) remains a conundrum in the uveitis field, which is mainly related to the diverse clinical phenotypes of TB-uveitis. Moreover, it remains difficult to differentiate whether Mycobacterium tuberculosis (Mtb) is present in the ocular tissues, elicits a heightened immune response without Mtb invasion in ocular tissues, or even induces an anti-retinal autoimmune response. Gaps in the immuno-pathological knowledge of TB-uveitis likely delay timely diagnosis and appropriate management. In the last decade, the immunopathophysiology of TB-uveitis and its clinical management, including experts' consensus to treat or not to treat certain conditions with anti-tubercular treatment (ATT), have been extensively investigated. In the meantime, research on TB treatment, in general, is shifting more toward host-directed therapies (HDT). Given the complexities of the host-Mtb interaction, enhancement of the host immune response is expected to boost the effectiveness of ATT and help overcome the rising burden of drug-resistant Mtb strains in the population. This review will summarize the current knowledge on the immunopathophysiology of TB-uveitis and recent advances in treatment modalities and outcomes of TB-uveitis, capturing results gathered from high- and low-burden TB countries with ATT as the mainstay of treatment. Moreover, we outline the recent progress of HDT development in the pulmonary TB field and discuss the possibility of its applicability to TB-uveitis. The concept of HDT might help direct future development of efficacious therapy for TB-uveitis, although more in-depth research on the immunoregulation of this disease is still necessary.

Presumed tuberculosis-related scleritis

AIMS

To evaluate the clinical characteristics and therapeutic outcome of patients with recurrent scleritis of unknown demonstrable aetiology and positive QuantiFERON-TB Gold In-Tube test (QFT).

METHODS

Retrospective chart review of the demographic, clinical, laboratory and therapeutic outcome data of 15 patients. Clinical characteristics as well as remission rate after standard antituberculous therapy (ATT) were assessed.

RESULTS

There were 9 men and 6 women with a mean age of 48.9 years (range, 32-73). Scleritis was diffuse in 10 patients (66.6%) and nodular in 5 patients (33.3%), 1 of them with concomitant posterior scleritis. It was bilateral in 7 patients (46.6%) and recurrent in all of them. Scleritis appeared after prior uveitis (10 patients, 66.6%) and/or with concomitant uveitis (5 patients, 33.3%) or peripheral keratitis (5 patients, 33.3%). Previous ocular surgery was found in 7 patients (46.6%). Previous extraocular tuberculosis (TB) infection or previous TB contact was detected in 11 patients (73.3%). No radiologic findings of active extraocular TB were detected. ATT was used in 15 patients, sometimes with the addition of systemic corticosteroids (5 patients) and methotrexate (1 patient); 14 patients achieved complete remission (93.3%).

CONCLUSION

Presumed TB-related scleritis may appear in recurrent scleritis of unknown origin and positive QFT. It may occur after prior uveitis and/or concomitantly with uveitis or peripheral keratitis, and it may be triggered by previous ocular surgery. No patients had evidence of concurrent active extraocular infection, although many had previous TB infection or TB contact. ATT was effective, sometimes with the addition of systemic corticosteroids and methotrexate.

Interferon-gamma release assay and chest X-ray to classify intraocular tuberculosis among clinically undifferentiated uveitis

BACKGROUND Tuberculosis (TB) is a common cause of intraocular inflammation in Indonesia. As no accurate biomarker can confirm the diagnosis, ophthalmologists often rely on systemic findings, such as tuberculin skin test, interferon-gamma release assay (IGRA), and chest X-ray (CXR) for TB suspicion. This study aimed to evaluate IGRA and CXR in classifying intraocular TB among patients with a clinically undifferentiated cause of uveitis. METHODS This cross-sectional study included 116 patients (a total of 163 affected eyes) with a clinically undifferentiated cause of uveitis. IGRA and CXR were performed as part of the workup. Data on visual acuity, anterior chamber inflammation grade, and anatomical classification of uveitis were recorded. As there were no confirmed ocular tuberculosis (OTB) in our cases, eyes were classified into probable OTB, possible OTB, and unclassified. RESULTS Overall, 93 patients (80.2%) with a clinically undifferentiated cause of uveitis had positive IGRA, whereas 10 (8.6%) had CXR results suggestive of TB. More than one-third of the patients were blind (visual acuity <3/60), and panuveitis was the commonest anatomical classification. A trend was identified in patients with panuveitis, who often showed ≥2+ cell anterior chamber inflammation (p for trend = 0.023), according to OTB criteria (probable OTB = 3/4, 75.0%; possible OTB = 44/67, 65.7%; unclassified = 2/9, 22.2%). Furthermore, the clinically undifferentiated uveitis cases were eligible to be stratified into probable (8.6%) and possible (75.0%) OTB categories after IGRA and CXR examinations. CONCLUSIONS The combination of IGRA and CXR is valuable for classifying and diagnosing TB-related uveitis. A multidisciplinary approach is essential when the cause of uveitis is unknown.

Tubercular serpiginous choroiditis

Tubercular association with serpiginous choroiditis, also called ‘serpiginous-like choroiditis’ or ‘multifocal serpiginoid choroiditis’ (MSC) is reported from world over, especially from endemic countries. Though the exact mechanism is not yet clear, a direct or indirect infectious trigger by Mycobacterium tuberculosis (MTB) is believed to cause choroiditis.

The link of immune mechanisms with ocular inflammation caused by MTB is emerging, and has been supported by both experimental and human data. The molecular and histopathological findings of tubercular serpiginous-like choroiditis have been demonstrated in clinicopathological reports, as well as in animal models. Young to middle-aged healthy males are more frequently affected. The choroiditis lesions of tubercular serpiginous-like choroiditis evolve as multifocal lesions, affecting the retinal periphery as well as posterior pole. They begin as discrete lesions, and spread in a serpiginoid pattern to become confluent. Fundus imaging including autofluorescence is extremely helpful in monitoring patients for response to therapy. Its diagnosis is essentially clinical. Corroborative evidence is obtained by a positive tuberculin skin test, or a positive QuantiFERON-TB Gold (Cellestis, Carnegie, Victoria, Australia) test, and/or radiological (chest X-ray or chest CT scan) evidence of TB elsewhere in the body. Systemic corticosteroids are the mainstay of therapy to control active inflammation, while ATT helps to reduce recurrence of inflammatory attacks. Immunosuppressive agents are indicated in cases with relentless progression, paradoxical worsening, or recurrent choroiditis.

Histological Diagnosis of Ocular and Periocular Tuberculosis 1945 - 2020

BACKGROUND

Ocular tuberculosis is a rare but important differential diagnosis for inflammatory conditions of all eye tissues, including the ocular surface and adnexa. Tissue diagnostics may prove challenging as some ocular tissues are difficult to biopsy and the detection of pathogens may be insensitive. We were interested in how many cases in the archive of the ophthalmopathological laboratory had been diagnosed with (peri)ocular tuberculosis since 1945.

MATERIALS AND METHODS

Retrospective analysis of historical records and specimens of the ophthalmopathology laboratory of the eye department at Freiburg university hospital. Systematic re-evaluation of available slides for presence of granuloma, necrosis, giant cells, acid fast bacteria, and chronic as well as acute inflammation, plus comparison of current and historic evaluations. In addition, we describe a recent case with tuberculoma of the iris.

RESULTS

There were 50,418 records archived since 1945, of which 23 specimens taken from 22 patients had been diagnosed as (peri)ocular tuberculosis. Of these, 22 (96%) were archived and available for re-interpretation. Four specimens (17%) had been excised from children. The most common tissues were enucleated eye globes (10/23, 44%), followed by the lacrimal sac (5/23, 22%) and conjunctiva (2/23, 9%). The most frequent histopathological findings were granulomas (23/23, 100%), chronic inflammation (22/23, 96%), giant cells (21/23, 91%), and necrosis (14/23, 61%). An acute inflammatory response was found in 4/23 specimens (17%). Ziehl-Neelsen stains for acid-fast bacteria had been performed in five cases, of which three were positive (60%). The greatest discrepancy between current and historical findings related to the presence of necrosis (59% consensus). In other findings, the consensus was high (78 - 96%). In a recent case of a patient with wasting syndrome attributed to lymphoma, histopathological workup of an iris tumour led to the diagnosis of tuberculosis.

CONCLUSION

Ocular tuberculosis is a rare but important histopathological differential diagnosis. In the available specimens, the classic finding of necrotizing inflammation was rarest and showed least consensus on histological re-evaluation. Other typical findings, such as giant cells and a predominantly lymphocytic infiltrate, are sometimes not found even with proven presence of Mycobacterium tuberculosis. They should not be considered essential in cases where there is strong clinical suspicion.

Ocular mycobacterial lesions in cats

Ocular mycobacterial infections are an under-recognized cause of morbidity in the domestic cat. This study aimed to explore the distribution, histopathological appearance, and severity of feline ocular mycobacterial lesions, and to characterize the immune cell population with immunohistochemistry. Routine histological staining with hematoxylin and eosin, and Masson’s trichrome, was performed to identify ocular lesions and assign an inflammation score based on the number of cells present. Acid-fast bacilli were detected with Ziehl-Neelsen, and immunohistochemistry for ionized calcium-binding adaptor protein-1 (Iba1), calprotectin, cluster of differentiation 3 (CD3), and Pax5 was undertaken on formalin-fixed paraffin-embedded tissue samples from 24 cases of ocular mycobacteriosis. Posterior or panuveitis with concurrent retinitis was identified in 20/24 cases (83%), with retinal detachment in 16/20 (80%) of these cases. Choroidal lesions had the highest median inflammation score. Ziehl-Neelsen-positive organisms were detected in 20/24 cases (83%), with the highest prevalence of acid-fast bacilli detected in choroidal lesions (16/20, 80%). Lesions were typically granulomatous to pyogranulomatous, characterized by abundant numbers of Iba1-positive macrophages, followed by calprotectin-positive granulocytes and monocytes, fewer T cells, and rarer B cells. However, where iritis was identified, inflammation was typically lymphoplasmacytic (11/16 cases, 69%). Where diagnostic testing was performed, tuberculosis (ie, infection with Mycobacterium bovis, Mycobacterium microti, or a nonspeciated Mycobacterium tuberculosis-complex pathogen) was diagnosed in 20/22 cats (91%), with Mycobacterium lepraemurium infection identified in the other 2/22 cats (9%). These results suggest the choroid is the primary site of lesion development in most cases of feline ocular mycobacteriosis, and inflammatory changes are associated with the presence of mycobacteria localized to ocular tissues.

Absence of Evidence as The Evidence Of Absence: The Curious Case of Latent Infection Causing Ocular Tuberculosis

Ocular tuberculosis (TB) is frequently considered as intraocular inflammation in the setting of latent TB, owing mainly to the absence of microbiological evidence of Mycobacterium tuberculosis in ocular fluid samples. Even though such lack of microbiological evidence, and of systemic signs of active TB disease, are suggestive of latent TB infection, molecular and rare histopathologic evidence of mycobacteria in the eye, and favourable response of ocular inflammation to anti-TB therapy point to the presence of active infection in ocular TB. Here, we discuss how intraocular inflammation in ocular TB is not merely an immunologic response to bacilli, but an active tuberculosis infection. We will discuss the reason for the frequent absence of microbiological evidence of TB in the eye in ocular TB and the diagnostic hierarchy to arrive at the diagnosis of this infectious uveitis entity.

Anti-TB monotherapy for choroidal tuberculoma: an observational study

BACKGROUND

Choroidal tuberculoma is possibly the most unequivocal manifestation of ocular infection with Mycobacterium tuberculosis. Here, we investigate the need for adjunctive corticosteroids in the management of this infection. We have compared the efficacy of anti-tubercular therapy (ATT) with or without oral corticosteroids, in management of choroidal tuberculoma.

METHODS

We report a retrospective, observational study of patients treated with ATT for choroidal tuberculoma. Group A patients were treated with standard 6-month ATT alone, and Group B with ATT and oral corticosteroids, with/without intravitreal triamcinolone/ bevacizumab injections. Primary outcome measure was time to complete resolution of lesions. Secondary measures were time to first sign of resolution and change in best corrected visual acuity (BCVA) at final visit.

RESULTS

Fourteen patients were included in the study-seven in Group A and seven in Group B. Both groups had similar duration of symptoms and size of lesions but not baseline BCVA (p = 0.02). Perilesional fluid was noted in all eyes in each group. Mean time to complete resolution in group A was 1.89 ± 0.28 (range 1.25-2) months, significantly lesser than group B (5.17 ± 2.64 [range 2-9] months, p = 0.005, Mann-Whitney test). Mean time to first sign of resolution (range from 5 days to 10 weeks, p = 0.35) and mean change in BCVA between presentation and final follow up (p = 0.2) were comparable between both groups.

CONCLUSION

Anti-TB monotherapy alone, may be sufficient for resolution of at least, select cases of choroidal tuberculoma, without the need for adjunctive corticosteroids.

Global prevalence and clinical outcomes of tubercular uveitis: a systematic review and meta-analysis

Tubercular uveitis (TBU) is an inflammation/infection of the eye secondary to Mycobacterium tuberculosis infection. The difficulty in making the diagnosis has resulted in variable prevalence and clinical response rates. We aimed to determine the global prevalence of TBU in uveitis patients stratified by TB high-burden countries (HBCs) and non-HBCs and by geographic regions and the clinical response of TBU to antitubercular treatment We performed a systematic review and meta-analysis of TBU studies published in PubMed, Scopus and EMBASE, up to June 30, 2020. A random effects model was used for all meta-analyses. Of 5,018 articles identified, 70 prevalence studies (65,607 uveitis and 3,166 TBU cases) and 18 clinical outcome studies (1,570 TBU cases; 1,304 responded to anti-tubercular therapy [ATT]) were analyzed. The overall weighted prevalence of TBU was 4.0% (95% CI, 3-5); in TB HBCs it was 7.0% (95% CI, 5-11), non-HBCs 3.0% (95% CI, 2-4), and sub-Saharan Africa 11.0% (95% CI, 8-15). The overall weighted clinical response was 82.0% (95% CI, 75-89). Despite the difficulty in diagnosing TBU, the prevalence is expectantly higher in HBCs, and sub-Saharan Africa and the clinical outcome is poor. Standardization of diagnostic criteria and ATT is warranted in future cohort studies.

Role of Extracellular Mycobacteria in Blood-Retinal Barrier Invasion in a Zebrafish Model of Ocular TB

Intraocular inflammation following mycobacterial dissemination to the eye is common in tuberculosis (TB)-endemic countries. However, the early host–pathogen interactions during ocular dissemination are unknown. In this study, we investigated the early events during mycobacterial invasion of the blood-retinal barriers (BRBs) with fluorescent-tagged Mycobacterium marinum (Mm), host macrophages, and retinal vasculature in a zebrafish model of ocular TB. We found that Mm invaded the vascular endothelium in either the extracellular or intracellular (inside phagocytes) state, typically 3–4 days post-injection (dpi). Extracellular Mm are phagocytosed in the retinal tissue and progress to form a compact granuloma around 6 dpi. Intracellular Mm crossing the BRBs are likely to be less virulent and either persist inside solitary macrophages (in most cases) or progress to loosely arranged granuloma (rarely). The early interactions between mycobacteria and host immune cells can thus determine the course of disease during mycobacterial dissemination to the eye.