How should a patient presenting with purpura and itching be evaluated and managed?

Evaluation and Management of Purpura with Itching

A patient presenting with purpura and itching requires immediate evaluation for immune thrombocytopenic purpura (ITP), vasculitis (particularly IgA vasculitis/Henoch-Schönlein purpura), and underlying hematologic malignancies, with initial workup including complete blood count with differential, platelet count, blood film, and assessment for systemic involvement.

Initial Diagnostic Approach

The combination of purpura and itching is clinically significant and demands systematic evaluation:

Essential Laboratory Testing

First-line investigations should include 1:

• Complete blood count with differential and blood film
• Platelet count (critical to assess for thrombocytopenia)
• Lactate dehydrogenase (LDH)
• ESR (if available)
• Liver and renal function tests
• Ferritin levels

Key Clinical Distinctions

Assess for thrombocytopenia immediately. If platelets are low (<100 × 10⁹/L), consider ITP as the primary diagnosis. The severity of bleeding risk correlates with platelet count, with counts <10-30 × 10⁹/L requiring urgent intervention 2.

If platelets are normal or elevated, investigate for:

• Polycythemia vera (PV): Look for raised hemoglobin/hematocrit, microcytosis (suggesting iron deficiency), raised white cell or platelet count, and low ESR. Order JAK2 V617F mutation testing (positive in up to 97% of PV cases) 1
• Lymphoma: Particularly if itching occurs at night with weight loss, fevers, or night sweats 1
• IgA vasculitis: Especially if purpura is palpable and located in dependent areas (lower extremities, buttocks) 3, 4

Specific Diagnostic Pathways

For Suspected IgA Vasculitis (Henoch-Schönlein Purpura)

Diagnostic criteria require 3:

• Palpable purpura in dependent areas
• Assessment for systemic involvement (abdominal pain, gastrointestinal bleeding, hematuria/proteinuria)
• Skin biopsy showing leukocytoclastic vasculitis with IgA deposition on immunofluorescence

Additional testing if systemic involvement suspected 3:

• Abdominal contrast-enhanced CT (shows intestinal wall thickening and edema)
• Small intestinal endoscopy (reveals diffuse hyperemia, edema, erosion)
• Urinalysis for proteinuria/hematuria
• If urine protein positive: ultrasound-guided renal biopsy with immunofluorescence (typically shows elevated IgA levels)

For Suspected Hematologic Disease

If polycythemia vera suspected 1:

• JAK2 V617F mutation testing (first-line)
• If JAK2 negative: serum erythropoietin, oxygen saturation, chest X-ray, abdominal ultrasound

If lymphoma suspected 1:

• Enlarged lymph nodes require excision or ultrasound-guided core biopsy
• Consider skin biopsy from trunk even if skin appears normal (rare cases of cutaneous lymphoma present with pruritus alone)

For "Itching Purpura" (Benign Entity)

This is a diagnosis of exclusion characterized by 5:

• Sudden onset of intensely pruritic purpuric lesions
• Normal hematologic and serologic evaluation
• Clinical appearance similar to progressive pigmented purpuric dermatoses
• Chronic course with exacerbations/remissions

Management Algorithms

ITP Management (if platelets <100 × 10⁹/L)

Treatment indications 2:

• Severe bleeding symptoms (always treat)
• Moderate bleeding or increased bleeding risk
• Platelet count <10-30 × 10⁹/L with troublesome purpura

First-line treatment options 2:

1. IVIg: 0.8-1 g/kg single dose (raises platelets in >80% of children; effective in adults)
2. Corticosteroids: Prednisone 1-2 mg/kg/day OR high-dose 4 mg/kg/day for 3-4 days
3. IV anti-D immunoglobulin: For Rh(D)-positive patients (caution: risk of hemolysis)

Emergency treatment (life-threatening bleeding) 2:

• 2-3× usual platelet transfusion dose
• High-dose IV corticosteroids
• IVIg or IV anti-D simultaneously

IgA Vasculitis Management

Combined therapy approach 3:

• Antihistamines for pruritus
• Gastric acid suppressants
• Glucocorticoids for abdominal pain, GI bleeding, and proteinuria
• Monitor for resolution of symptoms and urine protein normalization

Pruritus Associated with Hematologic Malignancy

For polycythemia vera-associated pruritus 1:

• First-line: Aspirin 300 mg daily (effective for PV-associated itch)
• Alternative options: Cytoreductive therapy, interferon-alpha, SSRIs, PUVA/UVB phototherapy, cimetidine, atenolol
• Emerging therapy: Ruxolitinib (JAK1/JAK2 inhibitor) shows rapid reduction in pruritus scores

For lymphoma-associated pruritus 1:

• Curative treatment of lymphoma resolves pruritus
• Symptomatic management: Cimetidine, gabapentin, carbamazepine, mirtazapine, or phototherapy
• Palliative care: High-dose oral corticosteroids

Critical Pitfalls to Avoid

1. Do not dismiss purpura with itching as benign dermatosis without checking platelet count—ITP can present with seemingly minor purpura but carries bleeding risk
2. Do not overlook malignancy screening in patients >60 years with diffuse itch <12 months duration 6
3. Do not delay treatment in ITP when platelets <10 × 10⁹/L, even without severe bleeding
4. Do not assume HSP is only a pediatric disease—adult presentation occurs and may be associated with underlying malignancy 7, 4
5. In IgA vasculitis, do not miss renal involvement—check urinalysis in all cases, as renal disease significantly impacts prognosis 3, 4