Here are some points from a NEJM review.
What is the current classification?
Primary versus secondary.
What is the significance of one designation over the other?
Primary Raynaud’s implies that there is no underlying connective tissue disease and hence a better prognosis. Primary Raynaud’s is not associated with digital ischemia. The secondary designation implies an underlying disease association.
How are the two types differentiated clinically?
Clinical criteria (history and physical exam) and nail fold capillaroscopy are the most important means. Serologic testing has an ancillary role.
Can primary Raynaud’s progress to secondary? What are the risk factors?
From the review:
One study showed that 37.2% of 3029 persons who were thought to have primary Raynaud’s phenomenon subsequently had a connective-tissue disease.11
Whether this reflects initial misdiagnosis or actual progression is unclear.
Concerning risk factors:
Recent studies have emphasized that factors such as the onset of Raynaud’s phenomenon near the age of 40 years, severe frequent events, and the presence of abnormal nailfold capillaries (Figure 1) can help predict whether a connective-tissue disease will develop11 and are especially helpful in identifying early scleroderma.13 A survey that followed 299 patients with primary Raynaud’s phenomenon for a median of 4 years showed that if capillaroscopy reveals normal nailfold capillaries and if all tests for scleroderma-specific antibodies are negative, then the chance that scleroderma will develop is less than 2%.
What are the disease associations in secondary Raynaud’s?
The following were listed in the review.
Connective tissue diseases: systemic sclerosis, SLE, dermatomyositis, sjogrens, mixed connective tissue disease and undifferentiated CTD.
Hematologic disorders: cryoglobulinemia, cryofibrinogenemia, cold agglutinin disease and paraneoplastic syndromes.
Miscellaneous causes include hypothyroidism, peripheral vascular disease and various drugs.