Assessment of the role of direct immunofluorescence of the outer root sheath in the diagnosis of pemphigus patients

Background Direct immunofluorescence (DIF) of perilesional skin has been established as a routine test for diagnosis of pemphigus. The outer root sheath (ORS) of the hair follicle (HF) is structurally analogous to epidermal keratinocytes. The pemphigus-specific immunofluorescence pattern seen in the skin has also been found in the ORS of plucked HFs. Use of anagen hair for detection of pemphigus-specific immunofluorescence is an easier, less-invasive procedure compared with DIF of skin. Objective To assess the role of DIF of the ORS of anagen hair in the diagnosis of pemphigus and compare it with DIF of perilesional skin. Patients and methods The present study was conducted on 30 patients with active pemphigus: 15 patients with other autoimmune diseases and 15 normal healthy individuals. All pemphigus patients were subjected to histopathological examination of lesional skin biopsies and DIF of perilesional skin using fluorescein isothiocyanate (FITC)-labeled monospecific anti-human immunoglobulin (Ig) G, IgA, and C3. Anagen hair with intact ORS were collected from the scalps of all studied individuals and examined for DIF using FITClabeled IgG, IgA, and C3. Results In pemphigus patients, all examined skin slides were positively stained for DIF on using FITC-labeled anti-human IgG, showing lace-like pattern of intercellular deposits in the epidermis, whereas 28 out of the 30 hair slides (93.3%) were positively stained for DIF on using FITC-labeled anti-human IgG, showing pemphigus-specific pattern with a sensitivity of 0.93 (95% confidence interval 0.76–0.99). The positivity of hair DIF using FITC-labeled IgG in pemphigus patients, patients with other autoimmune diseases, and normal healthy individuals was 93.3, 0.0, and 6.7%, respectively. Conclusion DIF on anagen hair ORS using FITC-labeled anti-human IgG promises to be a sensitive and specific tool for diagnosis of pemphigus; yet its reliability in follow-up of pemphigus patients needs further assessment.