Hair shaft abnormalities in alopecia areata evaluated by optical coherence tomography

Optical coherence tomography (OCT) is able to provide highly reproducible measurements of hair shaft thickness, including hair shaft diameter, cross-sectional surface area and hair shape, similar to histology but in vivo. Variations in the caliber of hair shafts have been described in patchy hair loss like alopecia areata (AA) using electron microscopy. The aim of this study was to evaluate whether OCT is useful for the evaluation of hair shaft abnormalities in AA.

The measurements were performed on patients with AA (n=9), aged 2-66 years. Fifty hairs from the border of an alopecic area and 50 hairs from an unaffected area without hair loss were examined using the OCT technique. The hair parameters were characterized by the cross-section (CS) and the form factor. The ratio of the maximal and minimal diameters of the hair at a fixed measuring distance from the scalp surface determined the form factor (d(max)/d(min)).

In all cases, the CS of hairs from an AA patch was significantly lower compared with hairs of an unaffected area. However, the form factor did not indicate any disturbances in hair growth.

The results demonstrate that structural abnormalities of hair shafts are found in active lesions of AA, but not in clinically unaffected hairs. The OCT technique is a promising method to gain more insight into the pathogenesis of AA in a non-invasive way.