Presyncopal symptoms in these patients have included dizziness, blurred vision, dyspnea, nuchal discomfort, and occasionally chest pain. The mechanism of the chest pain is not understood, but has been replicated in one patient by the administration of isoproterenol during the supine posture. It is therefore possible that it is somehow related to excessive pumping action of the heart associated with the intact parasympathetic withdrawal accompanying upright posture. The physical examination usually includes a normal or low normal supine blood pressure and a normal heart rate but a standing blood pressure that is less than 80 mmHg systolic. Heart rate rises on standing but appears to have an attenuated elevation given the very low blood pressure with upright posture.
Pupils are somewhat small but respond to light and accommodation.
Parasympatholytics dilate the eye appropriately. Many specialized tests differentiate these patients from those with familial dysautonomia. Cholinergic sensitivity as assessed by conjunctival methacholine was normal in that there was no response. Intradermal histamine evoked a typical flare reaction, whereas this does not occur in familial dysautonomia. These patients are further distinguished from familial dysautonomia in having normal tearing, intact corneal and deep tendon reflexes, normal sensory function and normal senses of taste and smell.