Raynaud's phenomenon is thought to be an exaggerated vascular response (abnormal vasoconstriction) to cold temperature or emotional stress that is clinically manifested by color changes of the skin of the digits. Color changes are often sharply demarcated and go through multiple stages as above (typically white, then blue, then red), however most experts agree that at least biphasic with pallor and cyanosis.
The prevalence of this disorder is thought to be between 3 to 5% in the general population, but this is an estimate since there is no gold standard for diagnosis (clinical as above).
A major challenge in treating Raynaud's is determining the cause:
Primary: diagnosed when no underlying disease is found in otherwise healthy individuals--and tends to be more common in younger patients and women (and be associated with normal nailfold capillaries)
Secondary: which is related to a systemic disease or other provoking factor and is often associated with abnormal nailfold capillary exam, especially in patients with a rheumatologic cause (especially systemic sclerosis)
•Autoimmune/Rheum: SLE, Scleroderma, Polymyostis/ Dermatomyositis, MCTD, Sjogrens
•Hematologic/Oncologic: Paraneoplastic, Cryoglobulinemia, Cold Agglutinin disease, paraproteinemia, POEMS
•Vascular: Emboli, Prinzmetals angina, Atherosclerosis, Thromboangiitis obliterans (with smoking)
•Neurological: Carpal Tunnel, Migraines
•Environmental: Vibration injury, Frost bite, Emotional stress
•Drugs/Toxins: Sympathomimetics, Chemotherapy, Nicotine, Cocaine, Ergotamines