Atypical pigmentary purpura: A clinical, histopathologic, and genotypic study

Background: The pigmentary purpuras (PPs) are a heterogeneous group of derm atoses defined by specific clincopathologic features but sharing, at the li ght microscopic level, superficially disposed dermal lymphocytic infiltrate s and hemorrhage. The term atypical pigmentary purpura (APP) is used by the authors in reference to cases of PP in which individual lesions, although clinically presenting as PP, show morphological features typically associat ed with mycosis fungoides (MF) including Sezary cells and epidermotropism. The integrated concept of lymphocyte atypia and PP is a confusing and enigm atic one to which reference in the literature has been previously made. Spe cifically, there are reports of PP presaging fully evolved MF, lymphoid aty pia has been identified in lesions of routine PP and MF with purpuric featu res has been described. The clinical, light microscopic, and genomic featur es of biopsied lesions showing. pathological features of APP and which clin ically were consistent with PP is explored. Design: The light microscopy of skin biopsy specimens from 34 patients with a pathological diagnosis of AP P was correlated to medical and drug histories. Zn 14 cases, adequate tissu e was present in the paraffin blocks to allow DNA extraction, The polymeras e chain reaction (PCR) was used in these 14 cases to explore for rearrangem ent of the T-cell receptor Fisher's exact test and pair wise exact tests we re used to assess the significance of histological differences between case s determined by clinical features to be of MF- or drug-related origin, or t o be idiopathic in nature. Results: Of 34 patients, 7 were held to have MF related PP; specifically these patients had violaceous, infiltrative, varia bly purpuric plaques on trunk, buttocks, and thighs accompanied by typical PP lesions which occurred either concomitant to or preceded the MF lesions. In 10 cases, a diagnosis of idiopathic PP was made whereby the clinical pr esentation was characteristic of PP; there were no concomitant lesions susp icious for MF and a drug-based origin was excluded. A drug-based origin was established in 17 patients based on lesional onset related to initiation ( 5 patients) and/or resolution after discontinuation (12 patients) of drugs including calcium channel blockers, lipid-lowering agents, beta-blockers, a ngiotensin-converting enzyme (ACE) inhibitors, antihistamines, antidepressa nts, or analgesics. There was considerable overlap histologically between a ll 3 groups including the degree of lymphoid atypia in the dermis, the pres ence of dermal-based Sezary cells, the degree and pattern of epidermotropis m, the paucity of other inflammatory cell elements, and the presence of lam inated dermal sclerosis, Morphological features predictive of MF related AP P over the other 2 groups were intraepidermal lymphocytes which were more a typical than the dermal-based infiltrate, Intraepidermal Sezary cells were less frequent in biopsies of drug-related APP relative to idiopathic PP (IP P) and MF related PP, PCR studies conducted in 14 cases (2 cases of MF, 6 c ases of drug-related APP, and 6 cases of IPP) revealed clonality in 2 cases of drug-related APP and 2 cases of IPP; the 2 studied MF-related cases did nor show clonal restriction. Conclusion: APP should not be equated with pu rpuric MF; it is not necessarily a precursor lesion of MF, and may be of dr ug-based origin. Clinical features are critical to the final assessment bec ause there is overlap pathologically in the 3 clinical subtypes of APP. HUM PATHOL 30:1004-1012. Copyright (C) 1999 by W.B. Saunders Company.