Myositis associated with multiple mononeuritis in eosinophilic granulomatosis with polyangiitis: an uncommon presentation

Abstract

Case Presentation: A 58-year-old man with adult-onset asthma and recurrent episodes of bloody diarrhea was admitted for ascending triparesis associated with distal paresthesia and lower limb muscle pain, which began approximately 15 days after an episode of febrile diarrhea. The patient reported unintentional weight loss of approximately 10 kg over 6 months. During hospitalization, he developed erythematous skin lesions on his extremities, one of which, on the fifth metatarsal, progressed to a necrotic lesion. Neurological examination revealed diffuse weakness, predominantly affecting the lower limbs, with absent crural reflexes and preserved brachial reflexes. Cerebrospinal fluid analysis showed neither albuminocytologic dissociation nor pleocytosis. Laboratory tests showed eosinophilia (16%), elevated CPK (1856 U/L), aldolase (32 U/L), and transaminases (AST 107; ALT 127). Electroneuromyography (ENMG) revealed subacute axonal sensorimotor multiple mononeuropathy with signs of activity. Magnetic resonance imaging of the thighs and upper limbs demonstrated muscle edema/hypersignal and contrast enhancement, consistent with inflammatory myopathy. Immunological investigation showed positivity for ANCA and anti-MPO, with negative anti-PR3. The patient was treated with intravenous immunoglobulin and high-dose steroid pulse therapy, showing functional improvement and was discharged with outpatient follow-up, able to ambulate with support. About a month later, he returned with hematuria and dyspnea, and died despite intensive care. Discussion: The positive ANCA/anti-MPO test, associated with the systemic clinical context, supported the diagnosis of eosinophilic granulomatosis with polyangiitis (EGPA), formerly known as Churg-Strauss syndrome. Among the neurological involvements in GEPA, painful multiple axonal mononeuritis stands out, demonstrated both clinically and electrophysiologically.Although less common, inflammatory myopathy has also been described within the spectrum of neuromuscular involvement of the disease. Despite initial improvement after treatment, subsequent progression with hematuria and alveolar hemorrhage highlights the potentially serious nature of this multisystemic disease. Final Comments: EGPA is a multisystemic inflammatory disease with a broad spectrum of neuromuscular manifestations. Given its dynamic and multi-organ nature, rigorous clinical and laboratory monitoring is recommended for early recognizement of potentially serious complications.