History and exam

Key diagnostic factors

common

pruritus

May precede clinical lesions by 3 to 4 months.

tense blisters on normal or erythematous skin

Blisters typically are found on the flexor surfaces of the arms and legs, axillae, groin, and abdomen.[5]

Other diagnostic factors

common

erythematous or urticarial plaques

Patients may also present with urticarial plaques that may evolve into blisters.

uncommon

oral lesions

Present in up to 30% of patients.[5]

Risk factors

strong

age 60 to 90 years

The mean age of onset is 65 years.[2] The highest prevalence is in people >90 years of age, with 398 (CI: 360 to 439) new cases per 1 million residents for men, and 87 (CI: 70 to 108) new cases per 1 million residents for women. The risk increases rapidly beyond the age of 60 years.[6] Prognosis is significantly influenced by patient age at diagnosis.[25][26]

major histocompatibility complex (MHC) class II allele (DQB1*0301)

There is a significant association with the DQB1*0301 allele in white people.[27]

weak

male sex

Data on sex differences are conflicting.[6][9][10] Some studies suggest the incidence may be higher in women until age 75 years, after which the incidence is higher in men.[10]

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