Approach to Purpura with Normal Platelet Count

Initial Clinical Assessment

Non-palpable purpura appears as flat, macular lesions that do not elevate above the skin surface, representing simple hemorrhage without vessel wall inflammation, typically occurring in areas of trauma or pressure 1
Palpable purpura indicates vessel wall inflammation (vasculitis) and requires a different diagnostic approach 1

The American Society of Hematology recommends ordering a complete blood count with peripheral blood smear examination as the fundamental first test, to examine red blood cell morphology and assess white blood cell morphology 2, 3, 4
Abnormal RBC or WBC morphology on smear, such as schistocytes or poikilocytosis, suggests alternative diagnoses like thrombotic microangiopathy, with a strength of evidence level of high 2, 5
The differential diagnosis includes vascular fragility disorders, drug-induced vascular damage, and coagulation disorders, with a recommendation to consider these causes based on clinical presentation and laboratory results 1

The European League Against Rheumatism recommends skin biopsy as crucial in the diagnosis of vasculitis, performing punch biopsy from the edge of a lesion including normal-appearing skin, requesting both H&E and direct immunofluorescence studies 7
Laboratory evaluation should include CBC with peripheral smear, renal and liver function tests, antiphospholipid antibodies, and antinuclear antibodies, with a strength of evidence level of moderate to high 7

The American College of Rheumatology recommends treatment of vasculitis with immunosuppressive therapy based on biopsy findings and extent of organ involvement, with a strength of evidence level of high 7
Treatment of vascular fragility typically requires no specific treatment beyond addressing underlying cause, such as vitamin C supplementation for scurvy, with a strength of evidence level of low to moderate 1