Diagnosis: Pigmented Purpuric Dermatosis (PPD) of the Hand
The most likely diagnosis is pigmented purpuric dermatosis (PPD) of the hand, a benign capillaropathy triggered by cold exposure that presents with non-blanchable purplish macules on the dorsal hand. 1
Clinical Reasoning
The presentation of sudden-onset, flat, non-palpable, non-blanchable magenta-purplish spots on the hand following cold exposure with thin gloves is highly characteristic of PPD affecting the hand. 1
Key Diagnostic Features Supporting PPD:
Non-blanchable purplish macules are the hallmark of PPD, representing extravasated erythrocytes and hemosiderin deposition in the superficial dermis 1
Unilateral dorsal hand involvement is the typical pattern for PPD localized to the hand, as documented in all 6 cases in the largest case series 1
Cold exposure as trigger is a recognized precipitating factor for PPD, with the thin gloves providing inadequate protection 2
Absence of pain, itching, and palpability distinguishes this from inflammatory conditions like vasculitis or cellulitis 1
Flat, non-palpable lesions indicate a superficial capillary process rather than deeper vascular involvement 1
Critical Differential Diagnoses to Exclude
Life-Threatening Conditions (Must Rule Out First):
Rocky Mountain Spotted Fever (RMSF) must be excluded if there is any fever, headache, or systemic symptoms, as the case-fatality rate is 5-10% and treatment delay increases mortality 3, 4
Meningococcemia presents with rapidly progressive petechial/purpuric rash with high fever, severe headache, and altered mental status 4
- The absence of systemic toxicity effectively excludes this diagnosis 4
Other Cold-Induced Dermatoses:
Chilblains (pernio) presents as inflammatory lesions on fingers/toes after cold exposure, but these are typically painful, pruritic, and erythematous rather than purplish and asymptomatic 5, 2
Raynaud phenomenon causes episodic tricolor changes (pallor, cyanosis, erythema) during cold exposure that resolve with rewarming, not persistent purplish macules 6, 7
Physiological livedo reticularis presents as a reticular (net-like) pattern rather than discrete purplish spots 2
Diagnostic Workup
Biopsy is required for definitive diagnosis because PPD of the hand is clinically considered in only a minority of cases due to its unusual presentation. 1
Expected Histopathologic Findings:
- Superficial perivascular lymphocytic infiltrate 1
- Extravasated erythrocytes in the dermis 1
- Hemosiderin deposition 1
- Absence of vasculitis or vessel wall necrosis 1
Laboratory Testing (If Systemic Disease Suspected):
- Complete blood count with differential to assess for thrombocytopenia or leukopenia (normal in isolated PPD) 3, 4
- Comprehensive metabolic panel to exclude systemic involvement (normal in isolated PPD) 3, 4
- Antinuclear antibody and rheumatoid factor only if connective tissue disease is suspected based on other clinical features 6, 7
Management Approach
PPD is a benign, self-limited condition that requires only reassurance and cold avoidance. 1
Conservative Management:
- Avoid cold exposure and ensure adequate hand protection with insulated gloves 2
- Maintain dry environment around the skin to prevent exacerbation 2
- Reassurance that this is a benign capillaropathy without systemic implications 1
When to Consider Treatment:
- No pharmacologic therapy is typically needed for isolated PPD of the hand 1
- If lesions are persistent or cosmetically concerning, topical corticosteroids may be considered, though evidence is limited 1
Critical Red Flags Requiring Immediate Action
Initiate doxycycline 100 mg twice daily immediately if ANY of the following develop: 3, 4
- Fever (temperature >38°C) 3, 4
- Severe headache 3, 4
- Myalgias or malaise 3, 4
- Progression of rash to involve trunk or other extremities 3
- Development of systemic symptoms within 24-48 hours 3