Objective. To examine the HLA-DRB1 associations of patients with erythema n
odosum (EN), establish HLA-DRB1 differences among patients with idiopathic
and secondary EN, and identify the HLA-DRB1 associations with specific cond
itions presenting with EN.
Methods. We conducted a retrospective study of 100 patients (83 women) with
biopsy proven EN diagnosed for a defined population in Northwest Spain. Pa
tients were classified into idiopathic or secondary if skin nodules occurre
d in the context of a well defined disease, or there was a precipitating ev
ent in close temporal relationship with the onset of EN. Patients and contr
ols were HLA-DRB1 genotyped from DNA using molecular based methods.
Results. At the time of diagnosis no precipitating events or underlying dis
eases were identified in 35 cases and, due to this, they were considered to
be idiopathic. Although strong associations do not appear to exist between
HLA-DRB1 and unstratified EN, the idiopathic group showed a significantly
lower frequency of HLA-DRB1*04 phenotype compared with controls. Among the
patients with secondary EN, the patient subgroup with sarcoidosis exhibited
a significantly increased frequency of HLA-DRB1*13 compared with healthy c
ontrols.
Conclusion. Idiopathic and some groups of secondary EN seem to have differe
nt HLA-DRB1 associations. These differences may have prognostic value in id
entifying patients with specific conditions associated with this syndrome.