Folliculitis in prurigo pigmentosa: a proposed pathogenesis based on clinical and pathological observation.
BACKGROUND
Prurigo pigmentosa is a rare inflammatory dermatosis whose exact etiology is not understood yet. The purpose of this study was to provide evidence of hair follicle involvement in the pathogenesis by analyzing its clinicopathologic features.


METHODS
Patients who fulfilled both the clinical and histological diagnostic criteria of prurigo pigmentosa were recruited. Their histopathologic findings, clinical features and medical histories were analyzed.


RESULTS
A total of 32 confirmed patients were enrolled from 2002 to 2013. Their ages ranged from 11 to 79 years with a female predominance. Patient lesions were primarily reddish-brown and located on the back. A total of 25 patients (78%) had pathological involvement of hair follicles, either bacterial colonies in the hair follicles (21/32, 66%), folliculitis (8/32, 25%) or perifolliculitis (15/32, 47%). There was a significantly higher proportion of patients with hair follicle involvement compared with control groups with either noninflammatory (5/43, 12%, p < 0.001) or inflammatory skin diseases (12/32, 38%, p = 0.002) on the back. Minocycline was an effective antibiotic treatment either singly or in combination with steroids.


CONCLUSIONS
The frequent presence of bacterial colonies along with sequelae of inflammatory changes on biopsy provides new evidence to support the theory that prurigo pigmentosa is a reactive inflammation associated with bacterial folliculitis.
Department of Pathology, Kathmandu University Birat Medical College and Teaching Hospital, Morang, Nepal.
Santosh U
SU
Kafle
MSI Skin and Laser Clinic, Mandalay, Myanmar.|Department of Dermatology, MacKay Memorial Hospital, Taipei, Taiwan.
Sai Myint
SM
Swe
Department of Dermatology, MacKay Memorial Hospital, Taipei, Taiwan.|Department of Medicine, MacKay Medical College, New Taipei City, Taiwan.|Department of Cosmetic Applications and Management, MacKay Medicine, Nursing and Management College, Taipei, Taiwan.
Pa-Fan
PF
Hsiao
Department of Dermatology, MacKay Memorial Hospital, Taipei, Taiwan.
Yi-Chiun
YC
Tsai
Department of Dermatology, MacKay Memorial Hospital, Taipei, Taiwan.|Department of Medicine, MacKay Medical College, New Taipei City, Taiwan.|Department of Cosmetic Applications and Management, MacKay Medicine, Nursing and Management College, Taipei, Taiwan.
Yu-Hung
YH
Wu
D000293:Adolescent; D000305:Adrenal Cortex Hormones / Q000627:therapeutic use; D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D000893:Anti-Inflammatory Agents / Q000627:therapeutic use; D002648:Child; D005260:Female; D005499:Folliculitis / Q000150:complications* / Q000188:drug therapy / Q000473:pathology*; D006633:Histamine Antagonists / Q000627:therapeutic use; D006801:Humans; D008297:Male; D008875:Middle Aged; D011536:Prurigo / Q000188:drug therapy / Q000209:etiology* / Q000473:pathology*; D055815:Young Adult
D000305:Adrenal Cortex Hormones; D000900:Anti-Bacterial Agents; D000893:Anti-Inflammatory Agents; D006633:Histamine Antagonists
bacterial colony; folliculitis; perifolliculitis; prurigo pigmentosa