OBJECTIVE To determine the prevalence and clinical significance of anti-Lam332 autoantibody detection from a large series of patients with MMP. DESIGN Multicenter retrospective study.
SETTING Four French national centers for autoimmune bullous diseases.
PARTICIPANTS One hundred fifty-four patients with MMP and 89 individuals serving as controls were included.
INTERVENTIONS Serum samples were analyzed by a new Lam332 enzyme-linked immunosorbent assay (ELISA); clinical and immunopathologic data were obtained from the patients’ medical records.
MAIN OUTCOME MEASURES The Lam332 ELISA scores were evaluated with respect to clinical characteristics, standard and salt-split indirect immunofluorescence, and bullous pemphigoid (BP) 230 and BP180-NC16A ELISAs.
RESULTS The Lam332 ELISA score was positive (≥9 U/mL) in 20.1% of serum samples from patients with MMP, 1 of 50 patients with bullous pemphigoid (BP), none of 7 with pemphigus, and 3 of 32 other controls. No relationship was evidenced between a positive ELISA Lam332 score and age; sex ratio; oral, ocular, genital, skin, or esophageal/laryngeal involvement; internal malignant neoplasm; or BP180 ELISA score. Salt-split skin indirect immunofluorescence and ELISA BP230 results were more frequently positive when Lam332 ELISA results were positive (P = .04 and .02, respectively). Patients with a positive Lam332 ELISA score frequently had more severe MMP (67.8% vs 47.2%; P = .04).
CONCLUSIONS AND RELEVANCE Results of this novel ELISA showed that serum anti-Lam332 autoantibodies are detected in 20.1% of patients with MMP. Anti-Lam332 autoantibodies are mainly detected in patients with severe MMP but not preferentially in those with a malignant neoplasm. The association between anti-Lam332 and anti-BP230 autoantibodies might arise from an epitope-spreading phenomenon.