Perforating Folliculitis Workup

Updated: May 25, 2018
  • Author: Suguru Imaeda, MD; Chief Editor: Dirk M Elston, MD  more...
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Laboratory Studies

In perforating folliculitis, perform renal function studies, including urinalysis, serum creatinine, and creatinine clearance, to evaluate for possible underlying renal disease, if warranted by history and/or physical findings.

Test blood glucose levels to evaluate for possible diabetes mellitus.


Imaging Studies

Imaging is not applicable to the evaluation of a patient with perforating folliculitis.



Skin biopsy for perforating folliculitis

Biopsy is indicated when uncertainty about the nature of an eruption exists, ie, whether or not it is a folliculitis. In particular, consultants in other specialties, such as nephrologists who are following patients for chronic renal failure, may wish to exclude vasculitis, an infectious process, or a drug eruption. Biopsy also helps distinguish perforating folliculitis from other inflammatory disorders of the hair follicle, such as irritant folliculitis, acneiform folliculitis, or infectious folliculitis (eg staphylococcal, Pseudomonas- induced, or Pityrosporum- induced folliculitis).

Since histopathologic findings in perforating folliculitis are focal, they can be missed if a skin biopsy is sectioned incompletely. As a result, a pathology report may be returned with a nonspecific diagnosis. To avoid this, a small punch biopsy that completely encompasses the lesion is recommended. The clinician should indicate on the accession form that perforating folliculitis is suspected and that multiple sections may be necessary to demonstrate diagnostic changes.


Histologic Findings

The involved hair follicle in perforating folliculitis shows focal disruption of its lateral wall, with a transepithelial channel and, often, a parakeratotic luminal plug. Connective-tissue elements, including collagen and elastin, and varying numbers of inflammatory cells can be found within this transfollicular channel and within the follicular lumen, admixed with parakeratotic keratin. In some cases, a hair shaft or hair fragment can be demonstrated within the follicular lumen and/or within the transfollicular channel. The dermis surrounding the follicle typically shows sparse inflammation and focal fibrosis.