Symptoms of Raynaud's syndrome in patients with fibromyalgia. A study utilizing the Nielsen test, digital photoplethysmography, and measurements of platelet α₂‐adrenergic receptors

Twenty‐nine female patients with fibromyalgia were questioned about symptoms of cold intolerance and Raynaud's syndrome; objective documentation of cold‐induced vasospasm was obtained by a Nielsen test. Twelve patients (41%) had abnormal Nielsen test results, and 11 patients (38%) had elevated levels of platelet α₂‐adrenergic receptors. There was a positive correlation between the percentage of change in finger systolic pressure on cooling (Nielsen test) and the number of α₂‐adrenergic receptors. There was poor correlation between Raynaud's syndrome symptoms and an abnormal Nielsen test result. Digital photoplethysmography showed a normal waveform in 2 of 3 patients. We hypothesize that a subgroup of patients with fibromyalgia syndrome have an up‐regulation of α₂‐adrenergic receptors as a cause of their exaggerated reaction to cold.