Four weeks after his only secukinumab injection, the patient reported another episode of acute worsening cutaneous symptoms. A 4-week prednisone taper starting at 40 mg/d was ordered. Computed tomography of the chest, abdomen, and pelvis to rule out internal malignancy was unremarkable. Around this time, the patient reported major emotional distress related to an unexpected death in his family, which added to a gradual increase in his stress level related to the COVID-19 pandemic.
Three weeks later, dapsone was increased to 100 mg twice daily on account of the patient’s adiposity and lack of cutaneous improvement on the lower dose. Subsequently, the vasculitis rapidly improved for 2 weeks. The patient then reported symptoms of headache, dizziness, and chills. He was tested for COVID-19 and was negative. Six weeks after increasing the dapsone dose (5 months after initial presentation), the skin was normalizing, showing only faintly hyperpigmented macules confined to areas of resolved vasculitis (forearms, abdomen, legs).
The patient had been on dapsone 100 mg twice daily for 3 months when he was started on ustekinumab (90 mg at weeks 0 and 4, with planned doses every 12 weeks) for psoriatic arthritis in hopes of withdrawing dapsone. His cutaneous symptoms have remained well controlled on this regimen for 18 months. Lowering of dapsone below 100 mg daily has resulted in recurrent mild vasculitis symptoms; he now maintains the once-daily dosing without negative side effects.
Comment
IgA vasculitis is a form of cutaneous small-vessel leukocytoclastic vasculitis (LCV) characterized by episodes of palpable purpura on the extensor surfaces of the arms and legs that may be associated with arthritis, abdominal pain, and/or hematuria. Although vasculitis is a known potential adverse effect of anti–tumor necrosis factor (TNF) α therapy, cases of adalimumab-induced IgA vasculitis are uncommon. As use of more targeted therapies for psoriasis and psoriatic arthritis, such as the IL-17 inhibitor secukinumab, increases so do reports of associated adverse events. Of 6 previously reported cases of secukinumab-associated vasculitis, at least 4 were IgA vasculitis (Table).1-6 Another case described one patient with rheumatoid arthritis undergoing secukinumab treatment who experienced necrotizing glomerulonephritis; however, the authors concluded secukinumab likely was not causative in that case, as serologies and urinalyses suggested gradual onset of the process prior to initiating the medication.7
The exact pathogenesis of IgA vasculitis is unclear, but a prevailing theory involves the dysregulation of IgA synthesis and metabolism. Other than increased serum levels of transforming growth factor β, which is a major stimulating factor for IgA production, it also has been hypothesized that the presence of aberrantly hypoglycosylated IgA exposes an autoepitope for recognition by other pathogenic IgG and IgA, leading to the formation of large immune complexes that can readily deposit in postcapillary venules. The deposition of IgA immune complexes in postcapillary venules and the subsequent activation of the complement system causes direct damage to the endothelial cells of vessel walls. This complement activation is evidenced by vascular complement component 3 deposition on DIF (a nonspecific feature of LCV). Chemotaxis of neutrophils ensues, followed by their firm adherence and transendothelial migration (mediated by monocyte chemoattractant protein 1 [MCP-1]). Neutrophil degranulation releases reactive oxygen species and cytokines, which in turn recruit additional leukocytes to the area of inflammation, subsequently undergoing degeneration (leukocytoclasis). Microvascular permeability also is enhanced by MCP-1, allowing exudation of serum, erythrocytes, and fibrin. In the setting of elevated circulating TNF and IL-1, endothelium is stimulated to activate the intrinsic and extrinsic coagulation pathways. This decreases endothelial fibrinolytic activity, leading to thrombosis. The high venous pressure and low fibrinolytic activity in the lower legs explains why vasculitic lesions often are confined to or begin in this distribution.1,8-10
There also are noteworthy roles for cytokines in LCV. Circulating transforming growth factor β and IL-6—which are necessary for development of T helper 17 (TH17) cells and production of IL-17—are higher in patients with LCV compared to controls. Peripheral blood monocytes in patients with LCV demonstrate higher production of IL-17. Once TH17 cells develop, their survival and phenotype are maintained by IL-23 (considered the master regulator of TH17 differentiation). IL-17 is a potent chemoattractant of IL-8 (CXCL8) and MCP-1, both of which promote neutrophil-mediated perivascular inflammation. The IL-23 and IL-17 pathways implicated in the pathogenesis of psoriasis also cause neutrophil activation and upregulate transcription of proinflammatory cytokines (IL-1, IL-6, IL-8, and TNF-α), which overlap with those implicated in LCV. Autoimmune disease generally entails some positive feedback loop of progressively severe self-recognition and tissue destruction by the immune system. These shared cytokinetic processes may explain how the internal environment of psoriasis could perpetuate IgA vasculitis.1,2,8,10-12
The mechanisms underlying vasculitis associated with adalimumab are unclear, but hypotheses involve direct toxicity on vessels, capillary deposition of anti-TNF/TNF immune complexes, or an inflammatory process resulting in autoantibodies. Similar hypotheses are posited for secukinumab-associated vasculitis, including deposition of secukinumab–IL-17 complexes. Anti–TNF-α medications may increase TH17 cell numbers, leading to increased production of IL-22 and a resultant immunologic microenvironment conducive to vasculitis. All 6 published cases of secukinumab-associated vasculitis that we found had received prior treatment with a TNF-α blocker, but only 1 had occurrence of vasculitis during that treatment.1-6,10