Perforating disorders are characterized by transepidermal elimination of altered keratin or dermal connective tissue material. These disorders include perforating folliculitis (as shown below), Kyrle disease, elastosis perforans serpiginosa, reactive perforating collagenosis, and acquired perforating dermatosis. Cases of overlap are described, and diagnostic criteria are not well-defined for all the entities.  Clinically, the lesions are hyperkeratotic to verrucous papules and nodules.
In perforating folliculitis, keratotic follicular papules develop, particularly over extensor surfaces. Microscopically, the disorder is characterized by disruption of the infundibular portion of the follicular wall, with transepidermal (transfollicular) elimination of connective-tissue elements and cellular debris.
Perforating folliculitis may present as an isolated finding, apparently unrelated to other disease states, but also can be associated with chronic renal failure and diabetes mellitus. Perforating folliculitis is closely related, if not identical, to the acquired perforating dermatosis that occurs with chronic renal disease. Kyrle disease (hyperkeratosis follicularis et parafollicularis in cutem penetrans) may simply represent an exaggerated form of perforating folliculitis. In addition, another disorder of transepidermal elimination, elastosis perforans serpiginosa, occasionally displays involvement of follicular units.
As in Kyrle disease, the concept of an extrinsic keratin plug penetrating the epidermis generally has been discredited. Abnormally premature keratinization at the expense of proliferation is a possible explanation, as proposed by Carter and Constantine and Tappeiner et al in Kyrle disease. [2, 3] A role for fibronectin has been postulated. In addition, a primary alteration of connective tissue or deposition of foreign material within the superficial dermis, with subsequent engulfment and elimination by proliferative follicular epithelium, also is conceivable as a mechanism. Such a response to experimental implantation of foreign material has been described.
In addition, evidence suggests a pathologic role for excessively coiled hairs. Mehregan first proposed that curled hairs within follicular canals may act as springs, penetrating the lateral follicular wall, thereby initiating the process of transepidermal elimination.  Support for this concept has been provided by an ultrastructural study of acquired perforating dermatosis that showed hair shaft fragments within transepidermal channels, even in patients in whom follicular involvement was not demonstrable on routine light microscopy. Factors that may promote coiling of hairs include follicular hyperkeratosis (occasional perforated follicles can be identified in keratosis pilaris) or contact dermatitis (eg, resulting from formaldehyde in clothing). Finally, trauma, such as scratching of pruritic skin, may well play a significant role in lesional development, possibly by setting in motion one or more of the pathologic events described above. 
A number of reported cases of perforating folliculitis appear to be idiopathic, but specific associations also have been observed. Although some associations could be coincidental, the association with chronic renal failure (including both dialysis-dependent and nondialysis patients) is relatively common, suggesting a pathogenetic link. [6, 7, 8, 9, 10, 11] Perforating folliculitis also is observed relatively commonly in association with diabetes mellitus.
Less common associations include sclerosing cholangitis, [12, 13] hypertension, atherosclerotic cardiovascular disease, acanthosis nigricans, psoriasis,  and phrynoderma.  A single case report described an association with Poland syndrome (unilateral absence of the pectoralis major muscle and ipsilateral symbrachydactyly), but this patient also had diabetes mellitus, hyperuricemia, and dilated cardiomyopathy.  A single case highlighted the presence of perforating folliculitis in a patient with human immunodeficiency virus infection.  A case of perforating folliculitis was also reported in a child with cystic fibrosis.  One case of perforating folliculitis arising in a patient with preexisting antisynthetase syndrome has been reported. 
Drug-induced cases include associations with infliximab and etanercept as possible inciting agents in a patient with rheumatoid arthritis  and dose-dependent association of sorafenib with skin lesions of perforating folliculitis. [21, 22, 23, 24, 25, 26] A report of a relationship with nilotinib suggests that drugs that inhibit c-kit and PDGF-R affect normal hair follicle development. PDGF-R has been previously linked in murine and human in vitro models to affect the hair follicle cycle.  A case of bendamustine-rituximab chemotherapy-induced perforating folliculitis was reported in 2017. 
Incidence of perforating folliculitis worldwide is not known precisely, although the disorder is not uncommon. In Detroit, Michigan, 50 cases were reported during a 2-year period in the early 1970s, although this observation was followed by a declining incidence of new cases.
Although generally no ethnic predilection has been identified, 1 study found a higher incidence of Kyrle disease in chronic renal failure among African American individuals.
Perforating folliculitis occurs equally in males and females; no sex predilection has been reported.
Perforating folliculitis is more common in the second through fourth decades of life.
Perforating folliculitis morbidity is associated with the cosmetic appearance of lesions and the pruritus that occasionally accompanies them. Although cutaneous disease is insignificant, substantial morbidity or mortality rates can be seen in association with the primary underlying diseases, such as diabetes mellitus or chronic renal failure.
Skin lesions can improve or clear, either spontaneously or with therapy. Further therapeutic experience may permit the development of specific treatment guidelines.
Reports of improvement of perforating folliculitis lesions with stabilization of renal damage (in patients with chronic renal failure) are encouraging and underscore the important role of internal medicine or surgery consultants in treating these patients.
Inform perforating folliculitis patients about the nature of the disease and its relation to any underlying medical condition that may be present.
Instruct perforating folliculitis patients to avoid rubbing or scratching the lesions, since this may result in their spread or in the development of secondary infection.
Fully inform patients about the treatment being used, including its proper use or application and possible adverse effects.
Abe R, Murase S, Nomura Y, et al. Acquired perforating dermatosis appearing as elastosis perforans serpiginosa and perforating folliculitis. Clin Exp Dermatol. 2008 Aug. 33(5):653-4. [Medline].
Carter VH, Constantine VS. Kyrle’s disease. I. Clinical findings in five cases and review of literature. Arch Dermatol. 1968 Jun. 97(6):624-32. [Medline].
Tappeiner J, Wolff K, Schreiner E. [Kyrle’s disease]. Hautarzt. 1969 Jan. 20(1):296-310. [Medline].
Mehregan AH, Coskey RJ. Perforating folliculitis. Arch Dermatol. 1968 Apr. 97(4):394-9. [Medline].
Pavlovic MD, Zecevic RD, Stamenkovic M, Stojadinovic O, Zolotarevski L. Trauma-induced perforating folliculitis. Eur J Dermatol. 2003 Nov-Dec. 13(6):592. [Medline].
Hurwitz RM. The evolution of perforating folliculitis in patients with chronic renal failure. Am J Dermatopathol. 1985 Jun. 7(3):231-9. [Medline].
White CR Jr, Heskel NS, Pokorny DJ. Perforating folliculitis of hemodialysis. Am J Dermatopathol. 1982 Apr. 4(2):109-16. [Medline].
Bilezikci B, Seckin D, Demirhan B. Acquired perforating dermatosis in patients with chronic renal failure: a possible pathogenetic role for fibronectin. J Eur Acad Dermatol Venereol. 2003 Mar. 17(2):230-2. [Medline].
Headley CM, Wall B. ESRD-associated cutaneous manifestations in a hemodialysis population. Nephrol Nurs J. 2002 Dec. 29(6):525-7, 531-9; quiz 540-1. [Medline].
Hong SB, Park JH, Ihm CG, Kim NI. Acquired perforating dermatosis in patients with chronic renal failure and diabetes mellitus. J Korean Med Sci. 2004 Apr. 19(2):283-8. [Medline].
Hurwitz RM, Melton ME, Creech FT 3rd, Weiss J, Handt A. Perforating folliculitis in association with hemodialysis. Am J Dermatopathol. 1982 Apr. 4(2):101-8. [Medline].
Kahana M, Trau H, Dolev E, Schewach-Millet M, Gilon E. Perforating folliculitis in association with primary sclerosing cholangitis. Am J Dermatopathol. 1985 Jun. 7(3):271-6. [Medline].
Mahajan S, Koranne RV, Sardana K, Mendiratta V, Damani A. Perforating folliculitis with jaundice in an Indian male: a rare case with sclerosing cholangitis. Br J Dermatol. 2004 Mar. 150(3):614-6. [Medline].
Patterson JW, Graff GE, Eubanks SW. Perforating folliculitis and psoriasis. J Am Acad Dermatol. 1982 Sep. 7(3):369-76. [Medline].
Neill SM, Pembroke AC, du Vivier AW, Salisbury JR. Phrynoderma and perforating folliculitis due to vitamin A deficiency in a diabetic. J R Soc Med. 1988 Mar. 81(3):171-2. [Medline].
Fistarol SK, Itin PH. Acquired perforating dermatosis in a patient with Poland syndrome. Dermatology. 2003. 207(4):390-4. [Medline].
Rubio FA, Herranz P, Robayna G, Pena JM, Contreras F, Casado M. Perforating folliculitis: report of a case in an HIV-infected man. J Am Acad Dermatol. 1999 Feb. 40(2 Pt 2):300-2. [Medline].
Tuttle MS, Kwon EJ, Tamburro J, Honda K. Perforating folliculitis in a patient with cystic fibrosis. Pediatr Dermato. 2010 Nov-Dec. 27(6):660-1.
Shaw KC, Kaley JR, Darling MD, Patterson JW, Chokoeva AA, Lotti T, et al. A case of perforating folliculitis in association with antisynthetase syndrome. J Biol Regul Homeost Agents. 2015 Jan-Mar. 29 (1 Suppl):95-8. [Medline].
Gilaberte Y, Coscojuela C, Vazquez C, Rosello R, Vera J. Perforating folliculitis associated with tumour necrosis factor-alpha inhibitors administered for rheumatoid arthritis. Br J Dermatol. 2007 Feb. 156(2):368-71. [Medline].
Wolber C, Udvardi A, Tatzreiter G, Schneeberger A, Volc-Platzer B. Perforating folliculitis, angioedema, hand-foot syndrome–multiple cutaneous side effects in a patient treated with sorafenib. J Dtsch Dermatol Ges. 2009 May. 7(5):449-52. [Medline].
Llamas-Velasco M, Steegmann JL, Carrascosa R, Fraga J, García Diez A, Requena L. Perforating folliculitis in a patient treated with nilotinib: a further evidence of C-kit involvement. Am J Dermatopathol. 2014 Jul. 36 (7):592-3. [Medline].
Minami-Hori M, Ishida-Yamamoto A, Komatsu S, Iiduka H. Transient perforating folliculitis induced by sorafenib. J Dermatol. 2010 Sep. 37 (9):833-4. [Medline].
Eberst E, Rigau V, Pageaux GP, Guillot B, Kluger N. Perforating folliculitis-like reaction related to sorafenib. Cutis. 2014 Jan. 93 (1):E8-10. [Medline].
Batalla A, Menéndez L, Blay P, Curto JR. Delayed onset perforating folliculitis associated with sorafenib. Australas J Dermatol. 2014 Aug. 55 (3):233-5. [Medline].
Kuiper EM, Kardaun SH. Late onset perforating folliculitis induced by lenalidomide: a case report. Br J Dermatol. 2015 Aug. 173 (2):618-20. [Medline].
Llamas-Velasco M, Steegmann JL, Carrascosa R, Fraga J, García Diez A, Requena L. Perforating Folliculitis in a Patient Treated With Nilotinib: A Further Evidence of C-kit Involvement. Am J Dermatopathol. 2013 Apr 22. [Medline].
Monteiro R, Bhat I, Abraham A, Rajlakshmi T. Perforating Folliculitis Secondary to Bendamustine-Rituximab Chemotherapy: A Case Report. Indian Dermatol Online J. 2017 Jul-Aug. 8 (4):290-292. [Medline].
Burkhart CG. Perforating folliculitis. A reappraisal of its pathogenesis. Int J Dermatol. 1981 Nov. 20(9):597-9. [Medline].
Ohe S, Danno K, Sasaki H, Isei T, Okamoto H, Horio T. Treatment of acquired perforating dermatosis with narrowband ultraviolet B. J Am Acad Dermatol. 2004 Jun. 50(6):892-4. [Medline].
Zachariae H, Sogaard H. Progressive generalized perforating folliculitis. Dermatologica. 1984. 168(3):131-7. [Medline].
Ashton RE, Montheith PG. Successful treatment of perforating folliculitis with 13-cis-retinoic acid. J Dermatol Treat. 1992. 3:67-8.
Suguru Imaeda, MD Chief of Dermatology, Yale University Health Services; Chief of Dermatology, Veterans Affairs Connecticut Healthcare System; Assistant Professor, Department of Dermatology, Yale University School of Medicine
Suguru Imaeda, MD is a member of the following medical societies: American Academy of Dermatology, American Medical Association, Connecticut State Medical Society, Sigma Xi, Society for Investigative Dermatology
Disclosure: Nothing to disclose.
Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference
Disclosure: Received salary from Medscape for employment. for: Medscape.
Rosalie Elenitsas, MD Herman Beerman Professor of Dermatology, University of Pennsylvania School of Medicine; Director, Penn Cutaneous Pathology Services, Department of Dermatology, University of Pennsylvania Health System
Rosalie Elenitsas, MD is a member of the following medical societies: American Academy of Dermatology, American Medical Association, American Society of Dermatopathology, Pennsylvania Academy of Dermatology
Disclosure: Received royalty from Lippincott Williams Wilkins for textbook editor.
Dirk M Elston, MD Professor and Chairman, Department of Dermatology and Dermatologic Surgery, Medical University of South Carolina College of Medicine
Dirk M Elston, MD is a member of the following medical societies: American Academy of Dermatology
Disclosure: Nothing to disclose.
Andrea Leigh Zaenglein, MD Professor of Dermatology and Pediatrics, Department of Dermatology, Hershey Medical Center, Pennsylvania State University College of Medicine
Disclosure: Received consulting fee from Galderma for consulting; Received consulting fee from Valeant for consulting; Received consulting fee from Promius for consulting; Received consulting fee from Anacor for consulting; Received grant/research funds from Stiefel for investigator; Received grant/research funds from Astellas for investigator; Received grant/research funds from Ranbaxy for other; Received consulting fee from Ranbaxy for consulting.
The authors and editors of Medscape Reference gratefully acknowledge the significant contributions of previous author, James W. Patterson, MD, to the development and writing of this article which has been recently updated.
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