The Diagnostic Challenge of Eosinophilic Granulomatosis With Polyangiitis Presenting as Acute Eosinophilic Myocarditis: Case Report and Literature Review

Abstract

Eosinophilic granulomatosis with polyangiitis (EGPA) is a systemic vasculitis involving small-to-medium-sized vessels characterized by asthma, vasculitis, and peripheral eosinophilia. EGPA-associated eosinophilic myocarditis (EM) occurs rarely, yet can be fatal if left untreated. Moreover, the accurate diagnosis of EGPA-associated EM without vasculitis is exceptionally difficult because of the overlapping features with EM of other causes. We report a case of probable EGPA with subclinical neurological involvement that presented with acute EM. The constellation of peripheral eosinophilia, left ventricular dysfunction, and normal epicardial coronary arteries raised suspicion of acute EM, which was confirmed by cardiac magnetic resonance (CMR) investigation and endomyocardial biopsy (EMB). Prompt systemic administration of corticosteroids completely restored and normalized myocardial structure and function. Although the patient's history suggested the presumed hypersensitivity myocarditis, EMB revealed EM without vasculitis, not hypersensitivity, leading to a tentative diagnosis of idiopathic hypereosinophilic syndrome. Interestingly, the characteristic findings of vasculitis on CMR imaging strongly suggested EGPA-associated EM. Although the patient had no clinical neurological manifestations, a nerve conduction study confirmed mononeuritis multiplex, leading to the final diagnosis of probable EGPA. Therefore, this case highlights the diagnostic challenge associated with EGPA and the diagnostic synergy of CMR and EMB for an exploratory diagnosis of EGPA-associated EM.

Keywords: CMR; EGPA; EMB; acute EM; corticosteroid treatment; hypereosinophilia.

Figure 1

Clinical effects of corticosteroid treatment on TTE. TTE on admission reveals diffuse and symmetrical LV wall thickening (11 mm), decreased cavity size, reduced ventricular function, and GLS values of the LV (LVDd, 44 mm; LVEF, 43%; and GLS, −9.9%; respectively) (A–C). Follow-up TTE on day 21 after corticosteroid therapy reveals a significant decrease in LV wall thickness (8 mm) with concomitant improvement in cavity size, ventricular function, and GLS values of the LV (LVDd, 48 mm; LVEF, 50%; and GLS, −17.5%; respectively) (D–F). Ao, aorta; GLS, global longitudinal strain; LA, left atrium; LV, left ventricle; LVDd, left ventricular end-diastolic diameter; LVEF, left ventricular ejection fraction; TTE, transthoracic echocardiography.

Figure 2

Changes in CMR findings in patients following corticosteroid treatment. CMR findings before (A–C) and after corticosteroid treatment (D–F). Myocardial first-pass perfusion imaging at rest (A,D), T2WI of the 2-chamber view (B,E), and LGE image (C,F). Ao, aorta; CMR, cardiac magnetic resonance; LGE, late gadolinium enhancement; LV, left ventricle; T2WI, T2-weighted image.

Figure 3

Endomyocardial biopsy findings. Photomicrograph with hematoxylin and eosin staining (A–C) (bars: A, 100 μm; B and C, 20 μm). Photomicrograph showing immunostaining against the major basic protein (D) (bar: 50 μm).