title: A reappraisal of the histologic findings of pigmented pretibial patches of diabetes mellitus.
abstract: BACKGROUND
  Pigmented pretibial patches (PPPs) are the most common cutaneous alterations in diabetes mellitus, found in up to 50% of diabetic patients. They classically present as flat-topped, dull-red papules on the pretibial areas, later becoming hyperpigmented and atrophic. Little is known regarding the pathogenesis of these lesions, and the histopathologic findings have been regarded as non-specific.
  
  
  METHODS
  We investigated the clinical and pathologic attributes of a series of 12 diabetic patients with PPP in an effort to discern any specific histologic attributes compared to normal skin removed from diabetic patients with cutaneous carcinoma.
  
  
  RESULTS
  All cases of PPP showed hyaline microangiopathy, all patients showed extravasated erythrocytes and/or hemosiderin deposits, and 10 patients showed an appreciable number of perivascular plasma cells. The average number of plasma cells per vascular plexus was 2.2. Control specimens removed from five diabetic patients showed hyaline microangiopathy, and three showed extravasated erythrocytes and hemosiderin. One patient showed a single vascular plexus with two plasma cells, p = 0.01.
  
  
  CONCLUSIONS
  The presence of increased dermal perivascular plasma cells in the appropriate clinical context might be an important and under-recognized clue for PPP. The pathogenic significance of this finding is unknown.
authors.affiliation: Department of Dermatology, Suncoast Osteopathic Hospitals, Bay Area Dermatology, Ameripath Tampa, FL, USA.
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Houck
authors.forename: Michael B
authors.initials: MB
authors.lastname: Morgan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D020405:Dermis / Q000098:blood supply / Q000473:pathology; D003924:Diabetes Mellitus, Type 2 / Q000150:complications / Q000473:pathology*; D003925:Diabetic Angiopathies / Q000150:complications / Q000473:pathology*; D005260:Female; D006801:Humans; D017495:Hyperpigmentation / Q000209:etiology / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D010950:Plasma Cells / Q000473:pathology; D013848:Thigh