Inflammatory Pseudotumor of the Spleen in a Patient With Psoriatic Arthritis: A Diagnostic Challenge in the COVID-19 Era

Abstract

The baseline inflammatory microenvironment in various organs of patients, which is shaped by pre-existing conditions and circulating drugs at the time before viral antigen exposure, may affect the severity of coronavirus disease-19 (COVID-19) infection and the nature of its complications. Inflammatory pseudotumor (IPT) of the spleen may represent one such complication that merits further investigation. We describe the case of a patient, who was under long-term treatment with a tumor necrosis factor inhibitor (TNFi), for psoriatic arthritis (PsA) and developed an inflammatory mass in the spleen, accompanied by systemic manifestations. This occurred with a history of four doses of nucleoside-modified messenger RNA (modRNA) vaccination for COVID-19 and shortly after a SARS coronavirus-2 (SARS-CoV-2) infection. Histologic examination of the splenectomy specimen supported by a large array of immunohistochemical stains and subsequent clinicopathological correlation indicated the diagnosis of splenic IPT in an immunologically altered background, due to modifying medication, immunization, and infection. Our case speculates that IPT may represent an adverse event related to immunogenicity of SARS-CoV-2, following antigen exposure (at first by sequential modRNA COVID-19 vaccinations and additionally by natural infection), despite the potentially protective effect of treatment with a TNFi.

Keywords: covid-19; disease modifying anti-rheumatic drugs; inflammatory pseudotumor; mrna-based vaccine; psoriatic arthritis; rheumatic disease; sars-cov-2; spleen; tumor necrosis factor-α(tnf-α) inhibitor.

Figure 1. Cross-sectional imaging and gross features

A. Preoperative upper abdomen magnetic resonance imaging revealing a prominent splenic mass; B. The cut surface of the surgical specimen shows a protruding spheroid mass with well-defined borders, brownish color, and solid texture.

Figure 2. Histopathological features

A, B. Red pulp substrate with fibroblastic reaction and moderate to severe inflammatory infiltrates, including "foamy" and iron-laden histiocytes, plasma cells, and lymphocytes; C. Immunohistochemical stain for CD68 highlighting histiocytes (A: hematoxylin-eosin, 100x; B: hematoxylin-eosin, 200x; C: streptavidin-biotin, 100x)