title: Physical urticaria: prevalence, type and natural course in a tropical country.
abstract: BACKGROUND
  Physical urticarias (PU) are an urticarial response to different specific physical stimuli. PU can occur concurrently with chronic spontaneous urticaria or another type of PU.
  
  
  OBJECTIVE
  We aimed to study the prevalence, type, clinical data and natural course of each type of PU and other inducible urticarias and also the prognostic factors for remission of patients visiting a tertiary referral hospital.
  
  
  METHODS
  We performed a retrospective study of 1200 chronic urticaria patients who visited our Urticaria Clinic during a period of 5 years.
  
  
  RESULTS
  Of the 1200 chronic urticaria patients, 86 (7.2%) were diagnosed as PU and other inducible urticarias. The most common type of PU was symptomatic dermographism (n = 35, 40.7%) followed by cold urticaria (n = 20, 23.3%) and delayed pressure urticaria (n = 11, 12.8%), respectively. Twelve patients (13.9%) had associated chronic spontaneous urticaria. None of the cases had multiple types of PU. Erythrocyte sedimentary rate elevation was the most common abnormal laboratory result. Nevertheless, only 4.6% declared a related infection. For each type, the median time after onset before 50% remission showed that cholinergic urticaria took the shortest course (34 months) and delayed pressure urticaria took the longest period (110 months). After 1 year and 5 years from the onset of symptoms, 13% and 50% of PU patients were free of symptoms, respectively.
  
  
  CONCLUSIONS
  This study emphasized the variety of PU, other inducible urticarias and natural courses based on tertiary hospital care. PU and other inducible urticarias have tendency to have a longer course than chronic spontaneous urticaria.
authors.affiliation: Department of Dermatology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: N
authors.initials: N
authors.lastname: Silpa-archa
authors.forename: K
authors.initials: K
authors.lastname: Kulthanan
authors.forename: S
authors.initials: S
authors.lastname: Pinkaew
mesh_terms: D000293:Adolescent; D000328:Adult; D001799:Blood Sedimentation; D002908:Chronic Disease; D003080:Cold Temperature / Q000009:adverse effects; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D011312:Pressure / Q000009:adverse effects; D015995:Prevalence; D011379:Prognosis; D012189:Retrospective Studies; D013785:Thailand / Q000453:epidemiology; D014581:Urticaria / Q000175:diagnosis* / Q000453:epidemiology* / Q000503:physiopathology; D055815:Young Adult