Investigation of the hair follicle inner root sheath in scarring and non-scarring alopecia.

BACKGROUND

Premature desquamation of the inner root sheath (IRS) is described as a defining histologic feature of follicular degeneration syndrome/central centrifugal cicatricial alopecia (CCCA). However, IRS abnormalities have been noted in other types of alopecia.

DESIGN

We evaluated the IRS in terminal hair follicles with transverse sections stained with hematoxylin-eosin and Ziehl-Neelsen stains in 22 non-scarring (7 areata and 15 androgenetic) and 21 scarring (13 CCCA, 2 lichen planopilaris, 2 lupus erythematosus, 1 folliculitis decalvans and 3 end stage) alopecia cases. In addition, we evaluated 15 normal controls with longitudinal sections to establish the level of IRS desquamation.

RESULTS

The IRS was present in 99.5 +/- 0.01% (mean +/- standard error) of normal follicles at the level of the arrector pili muscle/sebaceous gland/sweat gland coil (L2) and variably present at higher levels. The IRS was present at L2 in 97.9 +/- 1.5% of alopecia areata, 87.4 +/- 5.3% of androgenetic alopecia, 59.3 +/- 7.0% of CCCA and 49.4 +/- 11.3% of other scarring alopecia follicles.

CONCLUSIONS

Premature desquamation of the IRS was identified in CCCA; however, it was also noted in other scarring alopecia cases. IRS premature desquamation is a non-specific histologic feature in scarring alopecia and cannot be used alone as a defining feature of CCCA.