In distinguishing Raynaud's disease from Raynaud's phenomenon, which factor is significant?

Bilateral involvement is significant in distinguishing Raynaud's disease from Raynaud's phenomenon because it indicates a primary condition rather than a secondary one. Raynaud's disease is a primary condition that is typically characterized by bilateral symptoms, which means that both sides of the body (usually fingers or toes) are affected simultaneously. This bilaterality suggests a more idiopathic process, often with a more benign course.

In contrast, Raynaud's phenomenon occurs as a secondary condition and can present with unilateral involvement, especially when associated with other underlying diseases such as autoimmune disorders. The severity of symptoms can vary in both conditions and does not serve as a clear distinguishing factor. Similarly, the age of onset is not definitive; both conditions may present at various ages, thus making bilateral involvement a more reliable criterion for differentiation.