Introduction
Post-streptococcal uveitis is an infection caused by group A Streptococcal infection that can lead to post-streptococcal uveitis. This condition is often encountered among young patients presenting with acute bilateral non-granulomatous anterior uveitis. PSU is categorized as an infrequent entity, and a few cases have been reported. The exact mechanism for its occurrence remains unknown, but “autoimmunity” caused by molecular mimicry between bacterial antigens and self-antigens is suggested as a hypothesis for its occurrence. It undoubtedly emerges as a unique and challenging chapter within the narrative of ophthalmic disorders. Since there is a complex interplay between bacterial invasion and inflammatory responses, the eye stands as a “stage” where streptococcal infection unfolds.
What Is the Meaning of Uveitis?
Uveitis is the inflammation of the uvea. It is composed of a very diverse group of disease entities. It is estimated that about ten percent of blindness is caused by it. Based on the anatomical involvement of the eye, it is classified as - anterior, intermediate, posterior, and pan-uveitis. There are different ways in which uveitis has been classified, based on the duration it is based on standardization of uveitis nomenclature criteria (SUN). A diverse etiological agent, which includes a spectrum of infectious and non-infectious agents, has been implicated in its occurrence. It is an inflammatory process that primarily affects the uveal tissue and damages the retina, optic nerve, and vitreous. Hence, a uveitis specialist is expected to have a thorough knowledge of all entities, and their workup must include a complete systemic and ocular examination.
What Is Group A Streptococcus, and What Kind of Infection Does It Cause?
Group A Streptococcus (GAS) is also known as Streptococcus pyogenes. It is known to cause a very diverse spectrum of diseases that range from benign and self-limited infections of the skin and throat to lethal infections of soft tissues, leading to multiple organ failure. It remained a major cause of death in the industrialized countries caused by fatal epidemics. Subsequently, over the years, much awareness has been raised regarding the same, which has brought to focus its disproportionately high burden in resource-limited settings seen amongst the tropics. But still, an effective strategy is needed to prevent, treat, and accurately determine its worldwide burden. Pharyngitis remains the most common manifestation of GAS, peaking amongst school-aged children. The uveitis occurs two weeks post-streptococcal pharyngitis and remains an uncommon manifestation of post-streptococcal syndrome.
What Is Post Streptococcal Uveitis and How Does It Differ From Other Uveitis?
PSU often occurs after the infection is caused by group A Streptococci. The entire pathophysiology of its occurrence remains obscure. However, two theories have been proposed. The first is that immune-mediated reactions activate the CD-4 cells due to the production of cross-reactive antibodies following an acute infection. Further, ocular involvement occurs due to molecular mimicry between the beta-hemolytic streptococcal antigens and the retinal soluble antigens on the outer rod segments. Since GAS remains a very common infection, almost 600 million cases of pharyngitis have been reported worldwide. The PSU remains quite uncommon and scarce. It is evident among the younger population, especially children younger than 15. As with the consistent trend of GAS infection, PSU prevails in the months of winter and spring.
It is the etiology that differs PSU from the other forms of uveitis. PSU results from a preceding streptococcal infection in any other body part, such as the throat or skin. The inflammatory response that is seen in the eyes occurs as a result of the body’s reaction to bacterial infection.
What Are the Risk Factors Associated With Post Streptococcal Uveitis?
The most important risk factor include:
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Untreated GAS infection.
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Skin infection.
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Household crowding.
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Immunosuppression.
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Chronic illness.
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Underlying skin conditions.
What Are the Typical Symptoms and Signs of Post Streptococcal Uveitis?
The time lag between the initial infection and the appearance of ocular symptoms is at least two weeks, although it might range from three days to almost three years. Due to subclinical infection, the patient may not even report a history of streptococcal infection. The most classic presentation noted in PSU is non-granulomatous anterior uveitis and very fine inferior keratic precipitate and vitreous cells. In about 32 percent of cases, unilateral involvement is seen. A decreased visual acuity is found in a few patients. The anterior segment findings include bulbar conjunctival hyperemia, anterior scleritis, mutton fat keratic precipitate, and mild and fibrinous anterior chamber reaction with associated hypopyon.
The findings in the posterior segment include the following:
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Vitritis: Cellular infiltration that occurs in the vitreous body.
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Vitreal Cellular Reaction: A cellular response to the erythrocytes within the vitreous, ensuing inflammatory response.
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Retinal Periphlebitis: It is a vasculitis of peripheral retinal vasculature.
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Cystoid Macular Edema: It is a very common retinal disorder following cataract extraction.
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Secondary Glaucoma: This leads to optic nerve damage and loss of vision due to an increase in eye pressure.
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Optic Disk Swelling: The increase in the eye's intracranial pressure.
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Choroiditis: It is a rare condition that affects the outer retina; a gray lesion begins in the macular region.
The symptoms include:
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Blurred vision.
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Associated photophobia.
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Flu-like illness.
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Upper respiratory tract infection.
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Sore throat.
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Skin infection.
How Can the Diagnosis Be Established for Post Streptococcal Uveitis?
The diagnosis is indicated by ocular inflammation and other symptoms like pharyngitis and tonsillitis, with a positive throat culture. The laboratory testing includes Antistreptolysin O Titer (ASOT), determined by the patient's age, location, and season. Hence, its utility remains limited as a definitive diagnostic test. Despite this, ASOT must be considered in all the patients presenting with PSU, as its elevated reading suggests infection. A very high sensitivity (95.5 percent) and specificity (88.6 percent) is seen when a combination of ASOT and Anti DNase B is used.
There are other potential tests as well, like:
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ESR (erythrocyte sedimentation rate).
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CRP (C-reactive protein).
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Blood culture.
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Tuberculin skin test.
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Chest X-rays.
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Along with additional serological tests.
What Are the Management Strategies for Post Streptococcal Uveitis?
The treatment is mainly with Penicillin, the primary prevention strategy. The prevention must be restricted to only those exposed for more than 24 hours within one week. A multidisciplinary approach is opted for treating patients with PSU. An intramuscular dose of Penicillin or a week of oral Penicillin is used for active and residual streptococcal infection. As the severity of infection progresses, systemic corticosteroids are used. A very close clinical follow-up of the patients and serial monitoring of ASOT must be done. In cases where the ASOT picture worsens, antibiotic treatment is adopted. Surgical prophylaxis must be done through tonsillectomy to reduce the recurrent episodes of GAS pharyngitis.
Conclusion:
This condition challenges the diagnostic acumen, beckoning the exploration of further therapeutic strategies that can extend beyond the conventional approach. An enhanced clinical and preventive measure can be adopted by fostering a deeper comprehension of the link between uveitis and streptococcal infection. This can also be achieved by making sure there are experimental interventions that can enhance this further.
