title: Lymphoma rates are low but increased in patients with psoriasis: results from a population-based cohort study in the United Kingdom.
abstract: OBJECTIVE
  To determine if the rate of lymphoma in patients with a history of psoriasis is different from the rate of lymphoma in patients without psoriasis.
  
  
  METHODS
  Cohort study.
  
  
  METHODS
  Outpatient practices of general practitioners in the United Kingdom who contribute to the General Practice Research Database.
  
  
  METHODS
  The population studied was a sample of 10% of the patients 65 years or older registered with a general practitioner contributing to the General Practice Research Database between 1988 and 1996.
  
  
  METHODS
  The rate of lymphoma in patients with psoriasis compared with the rate of lymphoma in patients without psoriasis.
  
  
  RESULTS
  There were 2718 patients who had psoriasis and 105 203 patients (the reference population) who did not have psoriasis. The median follow-up time was 46 months. We noted 276 lymphomas. Patients with psoriasis had a 2.95 relative rate of developing lymphoma (95% confidence interval, 1.83-4.76) compared with those without psoriasis. This estimate did not change after controlling for age and sex using the Cox multivariable proportional hazards model. The rate of lymphoma changed little when the patients treated with methotrexate or those who developed mycosis fungoides were excluded. Compared with the reference population, we found an additional 122 lymphomas per 100 000 patients annually among patients with psoriasis who were 65 years or older.
  
  
  CONCLUSIONS
  These results indicate that patients with psoriasis are at increased risk for developing lymphoma. Additional studies are necessary to determine if the increased rate of lymphoma is related to psoriasis severity, psoriasis treatment, or an interaction between these risk factors.
authors: Department of Dermatology and the Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania, Philadephia 19104, USA.
authors: Joel M
authors: JM
authors: Gelfand
authors: Jesse
authors: J
authors: Berlin
authors: Abby
authors: A
authors: Van Voorhees
authors: David J
authors: DJ
authors: Margolis
mesh_terms: D000368:Aged; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008223:Lymphoma / Q000150:complications* / Q000453:epidemiology*; D008297:Male; D016016:Proportional Hazards Models; D011565:Psoriasis / Q000150:complications*; D012189:Retrospective Studies; D012306:Risk; D016019:Survival Analysis; D006113:United Kingdom / Q000453:epidemiology