Pure autonomic failure presenting as Harlequin syndrome.

Pure autonomic failure (PAF) is a progressive syndrome of neurogenic orthostatic hypotension, widespread anhidrosis, urinary retention, and constipation without other neurologic manifestations. It is generally considered a peripheral ganglionic synucleinopathy. Natural history studies have described risk factors for the conversion of PAF to Parkinson's disease, multiple system atrophy, or dementia with Lewy bodies, yet the early stages of PAF are not well characterized. We present a patient with unilateral anhidrosis, contralateral facial flushing and hyperhidrosis consistent with Harlequin syndrome that, over 6 years, progressed to PAF, suggesting that PAF may present with focal autonomic impairment prior to generalized autonomic failure.