[The so-called herpes gestationis factor in bullous pemphigoid].

We have investigated the presence of the so-called "herpes gestationis factor" in the serum of fifteen patients with bullous pemphigoid and one patient with cicatricial pemphigoid, that were negative for circulating anti-basement membrane antibodies, using the complement fixation test (substrate: human normal skin, 0 group). We have found herpes gestationis factor in 30% of the serologically negative patients. The presence in the serum of an auto-antibody IgG1 (HGF) highly avid for complement, may determine the false serological negativity in this patient.