What is the role of cytokeratins (CKs) testing in the workup of hidradenitis suppurativa (HS)?

Updated: Aug 30, 2019
  • Author: Marina Jovanovic, MD, PhD; Chief Editor: William D James, MD  more...
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Answer

The relationship of the sinus epithelium to the hair follicles and the apocrine glands has long been debated. [32] The sinus epithelium is clearly distinct from the normal epithelium of the subinfundibular ORS of the hair follicle. Thus, CKs 5 and 14 and Dsg2 always remain restricted to the basal cell layer of the sinus epithelium, whereas in the subinfundibular ORS, they are also expressed in the suprabasal layer. The relationship of the sinus epithelium to hair follicles and apocrine glands is in agreement with the theory that hidradenitis suppurativa lesions are caused by follicular plugging and subsequent rupture of the follicular epithelia. The exact role of inflammation in such patterns of differentiation has yet to be elucidated.

Thus, in another study of the hidradenitis suppurativa cytokeratin expression reported by Kurokawa et al, the draining sinus tract epithelium of hidradenitis suppurativa lesions were divided into 3 components: infundibular-like keratinized epithelium (type-A), noninfundibular keratinized epithelium (type B), and nonkeratinized epithelium (type C). [80] Types A and B were similar to the types I and II reported by Kurzen et al, [79] although CK17 was not detected in type A, suggesting fragility of this epithelial type. CK17, which is normally present in the suprabasal layers of healthy skin, represents a useful marker for differentiation of epithelial cells. It is a spacial keratin and has a function related to the maintenance of the 3-dimensional cytoskeleton structure of human adnexal glands. Thus, the absence of CK17 may reflect a fragile follicular structure, resulting in rupture of the follicle, which subsequently forms a subcutaneous abscess. [81]


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