Alopecia areata incognita: clinical characteristics and use of the Sinclair shedding scale.

Introduced in 1987, alopecia areata incognita (AAI), is incredibly difficult to diagnose. It presents as persistent, diffuse hair shedding while patients maintain normal hair density.1,2 We report 4 cases of AAI diagnosed in our specialty alopecia clinic, highlighting aspects of the condition that impart high levels of diagnostic suspicion. A chart review conducted between December 2017 and March 2022 yielded 4 patients with AAI. All patients were Caucasian females, average age of 45.3 years (SD = 10.9), with several years of excess scalp hair shedding. They denied telogen effluvium (TE) triggers or patchy hair loss. Initial differential diagnoses included female pattern hair loss (FPHL) and chronic telogen effluvium. Despite diligent treatment with >6 months oral spironolactone and/or oral low dose minoxidil, patients reported no improvement in shedding. All patients were noted to have a distinctive global appearance: normal density of 5–6-cm length terminal hairs on the top of the scalp and dramatically decreased density of longer terminal hairs distally (Fig. 1). Trichoscopy was unrevealing. AAI patients may develop circular patches of classic alopecia areata, but this was not observed in our initial evaluations.2,3 Scalp biopsies in all 4 patients varied with findings and the respective dermatopathologist favored diagnoses are listed in Table 1. Biopsy findings in AAI are subtle and vary depending on the disease stage.4,5 Histopathology in our patients was insufficient for a definitive diagnosis of alopecia areata incognita. Patients with AAI may collect 350–1000 hairs per day using the modified wash test.6 As the modified wash test is notably time consuming and difficult, we utilized the Sinclair shedding scale (SSS) to assess hair shedding.7 All patients reported >Grade 6 daily shedding on the SSS, representing about 750 hairs per day.7 Given our suspicion for AAI, we added monthly intralesional corticosteroid scalp injections at 5 mg/mL doses across the scalp. Patients did not use adjunct topical corticosteroids. After 2 treatment sessions, all patients reported SSS score improvement to the normal range and increased distal hair density (Fig. 1). One patient developed a few patches of subcentimeter classic alopecia areata that subsequently improved. Several AAI publications emphasize diagnosis based on growth phases and trichoscopy.2,3 We highlight an AAI clinical phenotype and demonstrate utility of the SSS when AAI is suspected. Originally developed to aid diagnosis of FPHL, the SSS is useful in assessing the response to treatment in women with varying hair lengths. Given that our patients had straight hair without improved SSS scores despite adequate treatment of FPHL, the SSS provided critical clinical estimates of shedding without extensive effort from patients or providers. The SSS