title: First-degree relatives are frequently affected in coeliac disease and dermatitis herpetiformis.
abstract: BACKGROUND
  Coeliac disease and dermatitis herpetiformis are phenotypically distinct gluten-sensitive diseases. Coeliac disease is known to cluster in families, whereas there is little evidence for dermatitis herpetiformis and for the occurrence of both diseases in the same families.
  
  
  METHODS
  The study group comprised 380 patients with coeliac disease and 281 patients with dermatitis herpetiformis, with a total of 3158 first-degree relatives, followed up for a mean of 14 years. The patients were questioned about affected first-degree relatives. The prevalence and incidence of biopsy-proven coeliac disease and dermatitis herpetiformis in relatives were determined.
  
  
  RESULTS
  Seventy-three (19.2%) patients with coeliac disease and 51 (18.1%) with dermatitis herpetiformis had affected first-degree relatives. The prevalence among relatives was similar for both diseases; 4.7% and 3.9% of the relatives had coeliac disease and 0.8% and 1.5% had dermatitis herpetiformis, respectively. The disease prevalence was 7% among siblings, 4.5% among parents and 3.5% among children. The annual incidence was 3/1,000 relatives, which is 15 times higher than among the general population. Coeliac disease and dermatitis herpetiformis were mixed in several multiple-case families.
  
  
  CONCLUSIONS
  The present long-term follow-up study of coeliac disease and dermatitis herpetiformis shows that every fifth patient can have affected first-degree relatives, and that the prevalence among relatives is 5.5%. Dermatitis herpetiformis segregates also in the families of patients with coeliac disease, and vice versa, indicating the same genetic background.
authors.affiliation: Dept of Dermatology, Tampere University Hospital and University of Tampere, Finland.
authors.forename: K
authors.initials: K
authors.lastname: Hervonen
authors.forename: M
authors.initials: M
authors.lastname: Hakanen
authors.forename: K
authors.initials: K
authors.lastname: Kaukinen
authors.forename: P
authors.initials: P
authors.lastname: Collin
authors.forename: T
authors.initials: T
authors.lastname: Reunala
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002446:Celiac Disease / Q000150:complications / Q000453:epidemiology* / Q000235:genetics*; D002648:Child; D003874:Dermatitis Herpetiformis / Q000150:complications / Q000453:epidemiology* / Q000235:genetics*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D007398:Interpersonal Relations; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D015995:Prevalence; D013997:Time Factors