Necrotizing scleritis is a rare and severe form with the highest proportion of underlying autoimmune conditions (85.7%), an older age of onset (> 45y/o) and the highest rate of complications, in contrast to other types of scleritis [7, 8]. Autoimmune diseases, such as rheumatoid arthritis, granulomatosis with polyangiitis (GPA), relapsing polychondritis, SLE, and PsA, are the most commonly associated entities [7, 9]. On the other hand, infectious causes are less common and are responsible for 5–10% of cases [10]. TB infections, which are endemic in the Philippines, were implicated in 4.2% of the cases in a study in an East Asian population [11]. Other infectious causes include HIV, herpes zoster, syphilis, Pseudomonas aeruginosa, Proteus, and Staphylococcus, with P. aeruginosa being the most common cause of infectious scleritis [7, 8, 9]. It has been suggested that the absence of an autoimmune pathology in necrotizing scleritis should alert the physician of a possible infectious etiology [7]. Clinically, infectious scleritis closely resembles autoimmune-associated scleritis and may be impossible to distinguish from one another without histopathologic confirmation. Therefore, it is essential to rule out an infectious etiology before initiating corticosteroids, as this can result in catastrophic complications should an infectious process be present.
Our case presented features most consistent with necrotizing anterior scleritis and keratouveitis in a patient with active psoriasis and PsA. The demographic data of the patient, a man belonging to an older age group, clearly fit the profile. Although we believe that an autoimmune mechanism is at play, the exact event that triggered the inflammatory cascade was not clearly defined, as he reported no history of trauma or surgery and no foci of infection were identified. Notwithstanding, the generally accepted immunopathogenesis is the overproduction of activated matrix metalloproteinases (MMPs) from inflammatory cells and scleral fibroblasts, which causes the breakdown of proteoglycans and collagen and destroys the scleral wall. T-helper cells and macrophages play important roles in inflammatory processes [7, 11]. Furthermore, the highly vascularized nature of episcleral tissue and the choroid beneath the avascular sclera makes it prone to develop vasculitis in autoimmune conditions, where the deposition of immune complexes may lead to more tissue damage. The focal areas of the white sclera observed in our patient represent capillary closure of the episcleral vasculature, which results in infarction and necrosis of the underlying sclera. The combination of severe vasculitis, infarction, necrosis, and choroid exposure causes severe pain and extreme scleral tenderness, consistent with the symptomatology of our patient. Most often adjacent ocular structures, such as the cornea, the ciliary body, and the trabecular meshwork are involved, manifesting as secondary corneal ulceration, peripheral ulcerative keratitis, uveitis, and increased intraocular pressure. These complications were clearly present in our case, except for IOP elevation; however, all were resolved with the initiation of systemic steroids. Although, recurrences have been reported by the Oasis Autoimmune Systemic Inflammatory Infectious Study (OASIS), and most of them were associated with necrotizing scleritis (26.6%) [11]. Therefore, periodic eye monitoring is imperative as part of the long-term management plan for these patients.
Topical NSAIDs are first-line agents but are generally avoided in acute scleritis due to the risk of scleral melt [12]. In addition, topical corticosteroids can cause delayed wound healing and perpetuate further scleral thinning. For severe non-infectious scleritis, such as in this case, systemic therapy with oral steroids is the preferred first-line treatment [7, 11]. The use of cyclosporine as a steroid-sparing agent or adjunctive therapy has been reported to be effective but methotrexate remains the first-choice treatment [7] However, recent developments have highlighted the successful use of biologics as steroid-sparing drugs to selectively target immune mediators in the inflammatory cascade.
Our patient had a recent bout of Covid-19 infection. On presentation, the patient tested negative for RTPCR. However, COVID-19 could have played a role in the exacerbation of psoriasis and its ocular manifestation. Covid-19 disease causes overwhelming inflammation in some patients, also known as cytokine storm, which is more destructive to organs than the disease itself [13]. In some cases, necrotizing anterior scleritis was reported in two patients who recovered from coronavirus. Both have no underlying autoimmune disorders. Ocular symptoms appeared 2–3 weeks after recovery from COVID-19 and were successfully treated with immunosuppressants and biologic agents [14]. Although there is no established link that can directly implicate Covid-19 and necrotizing anterior scleritis, it is widely accepted that Covid-19 is a pro-inflammatory condition that could have played a role in the exacerbation of ocular symptoms.