Immunoglobulin A-associated lymphocytic vasculopathy: a clinicopathologic study of eight patients.

INTRODUCTION: Cutaneous IgA-associated vasculitis can be a clue to Henoch-Schönlein purpura (HSP), which typically comprises renal and gastrointestinal tract disease and arthritis, whereby prominent and predominant IgA deposits within the cutaneous vasculature provoke a pustular leukocytoclastic vasculitis.

DESIGN: We describe eight patients with a novel expression of a cutaneous IgA vascular injury syndrome, namely a lymphoid vasculopathy which clinically and light microscopically resembled a pigmentary purpura (PP) in six, and correlate direct immunofluorescence (DIF) and clinical features to light microscopy.

RESULTS: Among associated diseases were prior viral infection, an HSP symptom complex, an undifferentiated connective tissue disease syndrome, lupus erythematosus profundus (LEP), Degos' disease and Berger's disease. Skin lesions comprised non-palpable petechial lesions involving lower extremities in all cases and also the upper extremities in two. A superficial perivascular lymphocytic infiltrate unaccompanied by vascular fibrin deposits was associated with prominent erythrocyte extravasation including into the epidermis. Mural and extravascular fibrin deposition was seen in one biopsy from a PP-like lesion and mural fibrinoid necrosis was seen in the cases of LEP and Degos' disease; in biopsies from these three cases, the presence of fibrin deposition warranted use of the appellation 'lymphocytic vasculitis'. In all patients, DIF showed prominent and predominant IgA deposits.

CONCLUSIONS: A non-necrotizing lymphocytic purpuric vascular reaction is one manifestation of vascular IgA deposition in the skin. A subpopulation of human lymphocytes bear surface Fc receptor and/or C3 receptors ('complement receptor lymphocytes') which can bind circulating immune complexes (ICs) or C3 generated via activation of the alternative complement cascade. Thus, circulating ICs are a potential pathogenic basis of this eruption, the histologic differential diagnosis of which is idiopathic PP and PP of drug or viral etiology.