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Perifollicular Lymphocytic Inflammation and Fibrosis in Dissecting Cellulitis: Evidence of a Consistent
Sanusi Umar1,2,3, Ochanya Ogah4, Jason Yang2
1Department of Medicine, University of California at Los Angeles, Los Angeles, CA, USA.
Clinical, Cosmetic and Investigational Dermatology
|July 22, 2026
Summary
Perifollicular infundibulo-isthmic lymphocytic inflammation and fibrosis (PIILIF) is a key finding in clinically normal scalp in dissecting cellulitis of the scalp (DCS). This inflammation is present even before active lesions appear, suggesting it
Area of Science:
- Dermatology
- Pathology
- Alopecia Research
Background:
- Dissecting cellulitis of the scalp (DCS) is a chronic suppurative alopecia.
- Perifollicular infundibulo-isthmic lymphocytic inflammation and fibrosis (PIILIF) is seen in other alopecias but not well-studied in DCS.
Purpose of the Study:
- To evaluate the presence and characteristics of PIILIF in clinically normal-appearing scalp (cNAS) and active/inactive lesions in patients with DCS.
- To investigate PIILIF as a potential subclinical histopathologic component of DCS.
Main Methods:
- Retrospective study of 12 male patients with DCS.
- Trichoscopy-guided biopsies of cNAS and active/inactive lesions.
- Histopathological analysis with CD4, CD8, CD117, and α-smooth muscle actin immunostaining.
Main Results:
- PIILIF was present in 100% of cNAS biopsies and all inactive nodules.
- Active lesions showed suppurative inflammation and remodeling superimposed on PIILIF.
- CD4+ lymphocytes and CD117+ mast cells were prominent in infiltrates.
Conclusions:
- PIILIF is consistently found in cNAS and inactive nodules in DCS patients.
- Active lesions exhibit suppurative destruction alongside PIILIF.
- PIILIF may be a subclinical histopathologic feature of DCS, warranting further research.
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