🖐️ Primary vs Secondary Raynaud's Differential Simulator

Cold-Triggered Digital Vasospasm

Cold or stress triggers a tri-phasic color change in the fingers.

• 3–5%: General population prevalence (varies by climate)
• ~4:1: Female-to-male ratio (primary form)
• 3 phases: Classic color sequence (white, blue, red)
• 15–20 min: Typical attack duration (per episode)

The vasospastic sequence

Digital arterioles spasm, then relax in a set order.

Pallor, cyanosis, rubor is the classic triad.

Primary vs secondary at first glance

Both share the trigger; downstream findings diverge.

Why differentiation matters

Secondary Raynaud's can herald serious systemic disease.

Age of Onset as a Screening Clue

Onset before 30 favors primary; after 30 favors secondary.

• <30 yo: Primary typical onset (often teens–20s)
• >30 yo: Secondary typical onset (new adult-onset flag)
• Benign: Primary lifetime course (rarely progresses)
• Scleroderma+: Secondary association (connective tissue disease)

Why age matters

Late-onset attacks warrant a broader autoimmune workup.

New onset after 30 is a screening red flag.

Primary onset pattern

Young patients, gradual onset, stable over decades.

Secondary onset pattern

Older onset often precedes overt autoimmune disease.

Bilateral Symmetry of Attacks

Primary attacks are symmetric; secondary attacks are often patchy.

• Bilateral: Primary symmetry (both hands equally)
• Asymmetric: Secondary symmetry (single digits spared/hit)
• Thumb: Digits usually spared (primary) (often unaffected)
• Common: Secondary single-digit onset (may start unilateral)

Reading the pattern

Compare left vs right hand digit-by-digit involvement.

Asymmetric or single-digit attacks suggest secondary disease.

Symmetric baseline

Primary disease affects fingers evenly on both hands.

Patchy involvement

Vascular or immune damage explains asymmetric secondary attacks.

Ulcers, Capillaries, and Autoantibodies

Three red flags strongly point toward secondary disease.

• Flag 1: Digital ulcers (tissue ischemia/necrosis)
• Flag 2: Abnormal nailfold capillaries (dropout, giant loops)
• Flag 3: Positive ANA / autoantibodies (scleroderma-spectrum markers)
• Refer: Any flag present (rheumatology workup)

Digital ulcers

Fingertip ulceration signals fixed vascular or tissue damage.

Ulcers essentially exclude a primary diagnosis.

Nailfold capillaroscopy

Dropout and giant capillaries mark microvascular disease.

Serology

Positive ANA raises pretest probability of connective tissue disease.

Classification Guides Management

Combined findings sort patients into two very different pathways.

• Conservative: Primary management (reassurance, warmth, avoid triggers)
• Workup: Secondary management (rheumatology + serology + capillaroscopy)
• Excellent: Primary prognosis (no organ threat)
• Disease-driven: Secondary prognosis (depends on underlying cause)

Primary pathway

Reassure, recommend warmth and trigger avoidance, monitor.

Most primary patients need no medication at all.

Secondary pathway

Refer for autoimmune workup and vascular protection.

Longitudinal watch

Reclassification can occur if new red flags appear.