Hypereosinophilic syndrome presenting with inflammation in the retroparotid space and showing Villaret's syndrome

Background Hypereosinophilia syndrome ( HES ) is a rare disease characterized by the association between hypereosinophilia and eosinophil‐mediated organ infiltration and damage or dysfunction. The cause of hypereosinophilia is classified as neoplastic, reactive and idiopathic. However, hypereosinophilia causes tissue and organ damage, regardless of the underlying etiology. The common manifestations are pulmonary, skin and gastrointestinal. Rarely, neurological lesions are manifested. As neurological lesions of HES , mononeuritis multiplex, radiculopathy, optic neuritis, meningitis and cerebral infarction have been reported. Case presentation A 43‐year‐old woman suffered from dysphagia and hoarseness, after symptoms of fever and sore throat 1 month earlier. On admission, her physical examination was unremarkable, except for neck pain on the right side. The neurological examination showed “Villaret's syndrome”: Horner's sign on the right side, and paralysis of the right glossopharyngeal nerve, vagus nerve, accessory nerve and hypoglossal nerve. Laboratory tests showed marked eosinophilia and it gradually worsened. The maximum eosinophil count increased to 3474/mm 3 . Magnetic resonance imaging showed a high‐intensity area with contrast effect spreading in the retroparotid space in the short T1 inversion recovery image, and a high‐intensity area spreading in the deep gray matter of the cerebrum in the fluid‐attenuated inversion recovery image. Treatment started with steroid pulse therapy. After therapy, eosinophils normalized on the next day, and multiple cranial nerve palsy improved gradually and normalized. Six months later, the abnormal signal of the retroparotid space had disappeared on magnetic resonance imaging . Conclusions HES is a multisystem dysfunction secondary to eosinophilic infiltration. In rare cases, HES causes inflammation in the retroparotid space and causes Villaret's syndrome.