Harlequin phenomenon associated with neurological abnormalities: A case report

Harlequin phenomenon consists of facial flush and erythrosis with unilateral sweating and pallor, associated with contralateral anhidrosis. We present the case of a child in whom the syndrome was associated with Horner's syndrome, epilepsy, mental and psychomotor retardation. A 9-year-old boy presented with right unilateral hemifacial erythema on effort, with normal colouring and Horner's syndrome on the left side of the face. His medical history revealed generalized myoclonic epilepsy, psychomotor delay and mental retardation. No underlying anomalies were identified. Harlequin phenomenon was diagnosed. Despite its stereotypical clinical features, Harlequin phenomenon is a poorly known disease. However, clinicians must be aware of it in order to determine the diagnosis and investigate for causes and any associated abnormalities. The underlying mechanism is an autonomic neuropathy affecting the sympathetic vasodilator neurons. To our knowledge, there have been no previous reports of Harlequin phenomenon in association with Horner syndrome, psychomotor delay and mental retardation.