Alopecia areata incognito: an elusive disease

Alopecia areata incognito (AAI) is an under-recognized variant of alopecia areata (AA) that can easily be misdiagnosed as telogen effluvium (TE) or androgenetic alopecia (AGA). Trichoscopy and histopathology studies in AAI are very few, and this disease entity merits wider recognition.

This is a case series of 30 patients of AAI from India, analyzing the clinical, trichoscopic, and histological features.

A total of 30 patients, 19 females and 11 males of mean age 32.3 ± 10.5 years, diagnosed with AAI from January 2019 to January 2022 were studied retrospectively. Trichoscopy was performed in all 30 cases. Trichoscopy-guided biopsy was done in 15 consenting patients. Transverse sections were studied for hair counts, ratios, and morphological features.

Diffuse hair thinning was noted, with 73% of patients showing predominant involvement of androgen-dependent scalp. Trichoscopy showed multiple yellow dots, short regrowing hair, and empty follicles. Circle hair or pigtail hair was noted in 77% of patients. Discrete black dots and exclamation-mark hair were seen in only six (20%). The most striking feature on histopathology was the presence of nanogen hairs (miniaturized non-anagen, anagen-like, telogen germ units, or indeterminate hairs) with a mean count of 34%, marking a shift toward telogen in mean anagen:telogen ratio of 1.3:1. Dilated infundibula and subtle peribulbar inflammatory infiltrate around miniaturized follicles and fibrous stellae were observed.

Trichoscopy-histopathology correlation helps to diagnose AAI and differentiate it from TE or AGA. This would help a clinician to provide better outcomes in hair regrowth.