title: Annular lichen planus: a case series of 20 patients.
abstract: BACKGROUND
  Annular lichen planus (ALP) is a long-recognized clinical variant of lichen planus, but is often considered uncommon in occurrence. The typical distribution and presentation of this variant have not been well described.
  
  
  OBJECTIVE
  We sought to better define the sites affected and clinical characteristics of the annular variant of lichen planus, along with the age and race of patients affected with this disorder.
  
  
  METHODS
  We conducted a retrospective review of 20 patients given a diagnosis of ALP during an 18-year period. The diagnosis was confirmed histologically in all but 3 cases of classic ALP that presented on the glans penis.
  
  
  RESULTS
  Patients ranged in age from 24 to 76 years. There were 18 men and 2 women; 15 were Caucasian and 5 were African American. Sites of involvement in order of decreasing frequency included: axilla (35%); penis (25%); extremities (25%); groin (including the inguinal creases and scrotum) (20%); back (15%); buttocks (10%); flanks (5%); neck (5%); and eyelids (5%). None of the patients had oral mucosal, vulval, scalp, or nail lesions. A total of 18 patients had purely annular lesions, whereas 2 of the 20 had a few purple polygonal papules in the vicinity of the annular forms. Some eruptions were macular, whereas the majority had a slightly raised edge with central clearing. In all, 6 patients had solitary lesions whereas only 4 had 10 or greater lesions. None exhibited a linear Koebnerized response or generalized lesions. Most patients were asymptomatic.
  
  
  CONCLUSIONS
  ALP commonly involves the male genitalia but also has a predilection for intertriginous areas such as the axilla and groin folds. Eruptions typically consist of a few lesions localized to one or a few sites. Distal aspects of the extremities, and less commonly the trunk, may also be involved. ALP is a subtype of lichen planus that may be more common than is reflected in the literature.
authors.affiliation: Department of Dermatology, University of Pennsylvania Medical Center, Philadelphia 19104-4283, USA.
authors.forename: Hilary L
authors.initials: HL
authors.lastname: Reich
authors.forename: Jane T
authors.initials: JT
authors.lastname: Nguyen
authors.forename: William D
authors.initials: WD
authors.lastname: James
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008010:Lichen Planus / Q000145:classification / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012867:Skin / Q000473:pathology