Immunofluorescence of the outer root sheath: an aid to diagnosis in pemphigus.

Background: The direct immunofluorescence (DIF) pattern of the outer root sheath (ORS) of the hair follicle in patients with pemphigus resembles that of perilesional skin. We performed DIF on anagen and telogen hair ORS from patients with pemphigus and compared the findings with those of perilesional skin.

Aim: To assess the sensitivity of DIF in the ORS of anagen and telogen hair in patients with pemphigus with positive DIF results in perilesional skin.

Methods: In total, 50 patients with active pemphigus and positive DIF findings in perilesional skin were selected for the study. Anagen hair was obtained from the scalp by the same method used for a trichogram, and telogen hair was selected by combing the hair and collecting the loose strands of hair from the comb. The hair type was further confirmed by microscopy. Hair samples were transported in Michel medium and prepared for DIF by mounting on a slide without sectioning. Anagen and telogen hair samples were also collected from 50 controls.

Results: Immunological deposits characteristic of pemphigus were found in the ORS of anagen and telogen hairs in all 50 patients, but in none of the 50 controls. Positive DIF findings were seen in scalp hair irrespective of the presence of scalp lesions. Of the 50 patients with pemphigus, 46 were diagnosed with pemphigus vulgaris, 2 with pemphigus vegetans, and 1 each with pemphigus foliaceus and pemphigus erythematosus, based on the clinical, histopathological and DIF findings. All the pemphigus variants had positive DIF findings in the ORS.

Conclusions: Using DIF on telogen hair ORS promises to be a useful tool for diagnosis and follow-up in cases of pemphigus.