Approach Considerations

The diagnosis of polymorphous light eruption (PMLE) is usually based on the clinical picture and history.

Laboratory Studies

In polymorphous light eruption (PMLE), laboratory tests can be performed to rule out other dermatoses such as erythropoietic protoporphyria or lupus erythematosus. Antinuclear antibody (ANA), anti-Ro (SS-A), and anti-La (SS-B) tests, as well as urine, stool, and blood porphyrin levels, should be obtained when clinically indicated.^[43]

Normal titers of ANA, as well as normal urine, stool, and blood porphyrin levels, support the diagnosis. A false-positive ANA can be seen, as a titer of 1:80 has been reported in up to 13% of normal population.

Other Tests

Results of phototesting in polymorphous light eruption (PMLE) patients are controversial, ranging from an ability to reproduce the eruption by repeat phototesting in 60-100% of patients to an inability to do so, except in patients who are very photosensitive.^[44]These differences may be explained by a lack of a standardized test procedures, variation in radiation sources used, and imprecision in diagnostic criteria for the disease. Minimal erythema doses (MEDs) are normal in PMLE and lowered or abnormal in chronic actinic dermatitis. In solar urticaria, irradiation results in reproduction of the lesion.

Photoprovocation test

Perform repetitive light testing; irradiating three times the MED to UVA on the right forearm and three times the MED to UVB on the left forearm for 3 consecutive days. Results are read immediately, at 24 hours, and at 72 hours. A delayed reading at 1 week may also be helpful. The test results are often positive in PMLE. A negative result does not exclude the diagnosis. If a lesion (eg, papule, vesicle) develops, biopsy confirmation can be performed. Histologically, a superficial and deep perivascular lymphocytic infiltrate is apparent with dermal edema. The test is best done in spring or early summer to avoid false-negative results. The area for testing should include a skin site previously involved with PMLE.

Photopatch tests

These can be used to rule out photoallergic or airborne contact. Two identical strips of standard photoallergens are placed on the back. One of the two strips is exposed to UVA radiation 24 hours later. Both the irradiated site and the unirradiated site are read at 24, 48, and 96 hours. A positive reaction at the irradiated site but not at the unirradiated patch test site is diagnostic of a photocontact allergy. Positive reactions at both the irradiated site and the unirradiated site are indicative of a contact allergy. According to Leroy et al in 2002,^[45]polychromatic phototesting seems to be more sensitive than UVA phototesting to assess PMLE, and results suggest UVB is a key trigger of PMLE.

Histologic Findings

The most striking feature of the biopsy specimen from a patient with polymorphous light eruption (PMLE) is edema in the upper part of the dermis. Tight, perivascular lymphocytic infiltrate is observed in the upper and mid dermis. When eczematous epidermal changes are present clinically, spongiosis, edema, dyskeratosis, and basal cell vacuolization may be observed. Occasionally, neutrophils and eosinophils may be present in the infiltrate. The dominant cell, however, is the lymphocyte. Mucin, which is thought to distinguish PMLE from lupus, can be present in skin biopsies of PMLE patients. A study of dermal mucin from lupus samples found that it is not so much different from that found in PMLE in comparison with other dermatitides, which also had some, but less, mucin (eg, erythema multiforme, fixed drug eruption, graft versus host disease, lichen planus, photodamaged skin).^[46]Erythema multiforme subtype can show evidence of a vacuolar interface with liquefactive degeneration of the dermoepidermal junction. A predominantly neutrophilic subtype also can be seen, which may be confused with Sweet syndrome. Chilblains has similar pathological features, but the history and location of the lesions can usually help make the diagnosis.

Note the images below.

Polymorphous light eruption pathology showing papillary dermal edema. Courtesy of DermNet New Zealand (https://www.dermnetnz.org/assets/Uploads/pathology/e/pmle-figure-1.jpg).

View Media Gallery

Polymorphous light eruption pathology showing papillary dermal edema. Courtesy of DermNet New Zealand (https://www.dermnetnz.org/assets/Uploads/pathology/e/pmle-figure-2.jpg).

View Media Gallery

Polymorphous light eruption pathology showing papillary dermal edema with lymphocytes in the epidermis (exocytosis). Courtesy of DermNet New Zealand (https://www.dermnetnz.org/assets/Uploads/pathology/e/pmle-figure-3.jpg).

View Media Gallery

Polymorphous light eruption pathology. The infiltrate is mainly lymphocytic but there may be intermixed eosinophils, neutrophils, and histiocytes. Courtesy of DermNet New Zealand (https://www.dermnetnz.org/assets/Uploads/pathology/e/pmle-figure-4.jpg).

View Media Gallery

Treatment & Management

Richards HL, Ling TC, Evangelou G, et al. Psychologic distress in polymorphous light eruption and its relationship to patients' beliefs about their condition. J Am Acad Dermatol. 2007 Mar. 56(3):426-31. [QxMD MEDLINE Link].
Guarrera M, Cardo P, Rebora AE, Schena D, Calzavara-Pinton P, Venturini M, et al. Polymorphous light eruption and benign summer light eruption in Italy. Photodermatol Photoimmunol Photomed. 2011 Feb. 27 (1):35-9. [QxMD MEDLINE Link].
Schmutz JL, Trechot P. [Polymorphous light eruption caused by ultraviolet C light]. Ann Dermatol Venereol. 2011 Aug-Sep. 138(8-9):639. [QxMD MEDLINE Link].
Millard TP, Bataille V, Snieder H, Spector TD, McGregor JM. The heritability of polymorphic light eruption. J Invest Dermatol. 2000 Sep. 115 (3):467-70. [QxMD MEDLINE Link].
McGregor JM, Grabczynska S, Vaughan R, Hawk JL, Lewis CM. Genetic modeling of abnormal photosensitivity in families with polymorphic light eruption and actinic prurigo. J Invest Dermatol. 2000 Sep. 115 (3):471-6. [QxMD MEDLINE Link].
Grabczynska SA, McGregor JM, Kondeatis E, Vaughan RW, Hawk JL. Actinic prurigo and polymorphic light eruption: common pathogenesis and the importance of HLA-DR4/DRB1*0407. Br J Dermatol. 1999 Feb. 140 (2):232-6. [QxMD MEDLINE Link].
Nakamura M, Bhutani T, Koo JY. Narrowband UVB-induced iatrogenic polymorphous light eruption: a case and suggestions to overcome this rare complication. Dermatol Online J. 2016 Jun 15. 22 (6):[QxMD MEDLINE Link].
Nomura Y, Uetsu N, Ueki Y, Yamazaki F, Noborio R, Okamoto H. Case of childhood polymorphous light eruption provoked by overlap exposure to ultraviolet A and B radiation. J Dermatol. 2017 Feb 2. [QxMD MEDLINE Link].
Kölgen W, van Meurs M, Jongsma M, van Weelden H, Bruijnzeel-Koomen CA, Knol EF, et al. Differential expression of cytokines in UV-B-exposed skin of patients with polymorphous light eruption: correlation with Langerhans cell migration and immunosuppression. Arch Dermatol. 2004 Mar. 140 (3):295-302. [QxMD MEDLINE Link].
Lembo S, Caiazzo G, Balato N, Monfrecola G, Patra V, Wolf P, et al. Polymorphic light eruption and IL-1 family members: any difference with allergic contact dermatitis?. Photochem Photobiol Sci. 2017 Sep 13. 16 (9):1471-1479. [QxMD MEDLINE Link].
Koulu LM, Laihia JK, Peltoniemi HH, Jansén CT. UV-induced tolerance to a contact allergen is impaired in polymorphic light eruption. J Invest Dermatol. 2010 Nov. 130(11):2578-82. [QxMD MEDLINE Link].
Schornagel IJ, Sigurdsson V, Nijhuis EH, Bruijnzeel-Koomen CA, Knol EF. Decreased neutrophil skin infiltration after UVB exposure in patients with polymorphous light eruption. J Invest Dermatol. 2004 Jul. 123(1):202-6. [QxMD MEDLINE Link].
Lembo S, Hawk JLM, Murphy GM, Kaneko K, Young AR, McGregor JM, et al. Aberrant gene expression with deficient apoptotic keratinocyte clearance may predispose to polymorphic light eruption. Br J Dermatol. 2017 Nov. 177 (5):1450-1453. [QxMD MEDLINE Link].
Lembo S, Raimondo A. Polymorphic Light Eruption: What's New in Pathogenesis and Management. Front Med (Lausanne). 2018. 5:252. [QxMD MEDLINE Link].
Lembo S, Fallon J, O'Kelly P, Murphy GM. Polymorphic light eruption and skin cancer prevalence: is one protective against the other?. Br J Dermatol. 2008 Dec. 159 (6):1342-7. [QxMD MEDLINE Link].
Patra V, Mayer G, Gruber-Wackernagel A, Horn M, Lembo S, Wolf P. Unique profile of antimicrobial peptide expression in polymorphic light eruption lesions compared to healthy skin, atopic dermatitis, and psoriasis. Photodermatol Photoimmunol Photomed. 2018 Mar. 34 (2):137-144. [QxMD MEDLINE Link].
Muhlbauer JE, Mihm MC Jr, Harrist TJ. Papular polymorphous light eruption. Fibrin, complement, and immunoglobulin deposition. Arch Dermatol. 1984 Jul. 120 (7):866-8. [QxMD MEDLINE Link].
Norris PG, Barker JN, Allen MH, et al. Adhesion molecule expression in polymorphic light eruption. J Invest Dermatol. 1992 Oct. 99(4):504-8. [QxMD MEDLINE Link].
Stephansson E, Ros AM. Expression of intercellular adhesion molecule-1 (ICAM-1) and OKM5 in UVA- and UVB-induced lesions in patients with lupus erythematosus and polymorphous light eruption. Arch Dermatol Res. 1993. 285(6):328-33. [QxMD MEDLINE Link].
Aubin F. Why is polymorphous light eruption so common in young women?. Arch Dermatol Res. 2004 Oct. 296(5):240-1. [QxMD MEDLINE Link].
Zirbs M, Pürner C, Buters JT, Effner R, Weidinger S, Ring J, et al. GSTM1, GSTT1 and GSTP1 gene polymorphism in polymorphous light eruption. J Eur Acad Dermatol Venereol. 2012 Jan 9. [QxMD MEDLINE Link].
Metelitsa AI, Lauzon GJ. Tobacco and the skin. Clin Dermatol. 2010 Jul-Aug. 4:384-90. [QxMD MEDLINE Link].
Majoie IM, van Weelden H, Sybesma IM, Coenraads PJ, Sigurdsson V. Polymorphous light eruption-like skin lesions in welders caused by ultraviolet C light. J Am Acad Dermatol. 2010 Jan. 62(1):150-1. [QxMD MEDLINE Link].
Draelos ZK, Hansen RC. Polymorphic light eruption in pediatric patients with American Indian ancestry. Pediatr Dermatol. 1986 Nov. 3(5):384-9. [QxMD MEDLINE Link].
Hönigsmann H. Polymorphous light eruption. Photodermatol Photoimmunol Photomed. 2008 Jun. 24(3):155-61. [QxMD MEDLINE Link].
Benanni B, Bruckner T, Bock M, et al. Low incidence of polymorphous light eruption in renal transplant recipients. Acta Derm Venereol. 2007. 87(4):372-4. [QxMD MEDLINE Link].
Deng D, Hang Y, Chen H, Li H. Prevalence of photodermatosis in four regions at different altitudes in Yunnan province, China. J Dermatol. 2006 Aug. 33(8):537-40. [QxMD MEDLINE Link].
Sharma VK, Sahni K, Wadhwani AR. Photodermatoses in pigmented skin. Photochem Photobiol Sci. 2013 Jan. 12:65-77. [QxMD MEDLINE Link].
Chen YA, Lee JY. Clinicopathologic study of solar dermatitis, a pinpoint papular variant of polymorphous light eruption in Taiwan, and review of the literature. J Formos Med Assoc. 2013 Mar. 112(3):125-30. [QxMD MEDLINE Link].
Isedeh P, Lim HW. Polymorphous light eruption presenting as pinhead papular eruption on the face. J Drugs Dermatol. 2013 Nov. 12(11):1285-6. [QxMD MEDLINE Link].
Kerr HA, Lim HW. Photodermatoses in African Americans: a retrospective analysis of 135 patients over a 7-year period. J Am Acad Dermatol. 2007 Oct. 57(4):638-43. [QxMD MEDLINE Link].
Nakamura M, Henderson M, Jacobsen G, Lim HW. Comparison of photodermatoses in African-Americans and Caucasians: a follow-up study. Photodermatol Photoimmunol Photomed. 2014 Oct. 30(5):231-6. [QxMD MEDLINE Link].
Naleway AL, Greenlee RT, Melski JW. Characteristics of diagnosed polymorphous light eruption. Photodermatol Photoimmunol Photomed. 2006 Aug. 22(4):205-7. [QxMD MEDLINE Link].
Jansen CT. The natural history of polymorphous light eruptions. Arch Dermatol. 1979 Feb. 115(2):165-9. [QxMD MEDLINE Link].
Lugovic Mihic L, Bulat V, Situm M, Cavka V, Krolo I. Allergic hypersensitivity skin reactions following sun exposure. Coll Antropol. 2008 Oct. 32 Suppl 2:153-7. [QxMD MEDLINE Link].
Aljasser MI, Lui H, Ball NJ, Kalia S. Persistent polymorphous light eruption after ultraviolet A1 phototherapy. Photodermatol Photoimmunol Photomed. 2013 Feb. 29:52-4. [QxMD MEDLINE Link].
Kontos AP, Cusack CA, Chaffins M, Lim HW. Polymorphous light eruption in African Americans: pinpoint papular variant. Photodermatol Photoimmunol Photomed. 2002 Dec. 18(6):303-6. [QxMD MEDLINE Link].
Chiam LY, Chong WS. Pinpoint papular polymorphous light eruption in Asian skin: a variant in darker-skinned individuals. Photodermatol Photoimmunol Photomed. 2009. 25:71-4. [QxMD MEDLINE Link].
Molina-Ruiz AM, Sanmartín O, Santonja C, Kutzner H, Requena L. Spring and summer eruption of the elbows: A peculiar localized variant of polymorphous light eruption. J Am Acad Dermatol. 68. 2013 Feb:306-12. [QxMD MEDLINE Link].
Balasubramanian P, Jagadeesan S, Sekar L, Thomas J. An interesting observation of polymorphous light eruption occurring on hypopigmented scars. Indian Dermatol Online J. 2015 Jul-Aug. 6 (4):294-6. [QxMD MEDLINE Link].
Totten JE, Brock DM, Schimelpfenig TD, Hopkin JL, Colven RM. Prolonged Exposure Dermatosis: Reporting High Incidence of an Undiagnosed Facial Dermatosis on a Winter Wilderness Expedition. Wilderness Environ Med. 2015 Dec. 26 (4):525-30. [QxMD MEDLINE Link].
Gronhagen CM, Gunnarsson I, Svenungsson E, Nyberg F. Cutaneous manifestations and serological findings in 260 patients with systemic lupus erythematosus. Lupus. 2010 Sep. 19(10):1187-94. [QxMD MEDLINE Link].
Popovic K, Nyberg F, Wahren-Herlenius M, Nyberg F. A serology-based approach combined with clinical examination of 125 Ro/SSA-positive patients to define incidence and prevalence of subacute cutaneous lupus erythematosus. Arthritis Rheum. 2007 Jan. 56(1):255-64. [QxMD MEDLINE Link].
Schornagel IJ, Guikers KL, Van Weelden H, Brijnzeel-Koomen CA, Sigurdsson V. The polymorphous light eruption-severity assessment score does not reliably predict the results of phototesting. J Eur Acad Dermatol Venereol. 2008 Jun. 22(6):675-80. [QxMD MEDLINE Link].
Leroy D, Dompmartin A, Verneuil L, Michel M, Faguer K. [Polychromatic phototest sensibility is superior to UVA phototest in polymorphic light eruptions]. Ann Dermatol Venereol. 2002 Jun-Jul. 129(6-7):860-4. [QxMD MEDLINE Link].
Vincent JG, Chan MP. Specificity of dermal mucin in the diagnosis of lupus erythematosus: comparison with other dermatitides and normal skin. J Cutan Pathol. 2015 Oct. 42 (10):722-9. [QxMD MEDLINE Link].
DeLeo VA, Clark S, Fowler J, Poncet M, Loesche C, Soto P. A new ecamsule-containing SPF 40 sunscreen cream for the prevention of polymorphous light eruption: a double-blind, randomized, controlled study in maximized outdoor conditions. Cutis. 2009 Feb. 83(2):95-103. [QxMD MEDLINE Link].
Bissonnette R, Nigen S, Bolduc C. Influence of the quantity of sunscreen applied on the ability to protect against ultraviolet-induced polymorphous light eruption. Photodermatol Photoimmunol Photomed. 2012 Oct. 28(5):240-3. [QxMD MEDLINE Link].
Murphy GM, Logan RA, Lovell CR, Morris RW, Hawk JL, Magnus IA. Prophylactic PUVA and UVB therapy in polymorphic light eruption--a controlled trial. Br J Dermatol. 1987 Apr. 116(4):531-8. [QxMD MEDLINE Link].
Bilsland D, George SA, Gibbs NK, Aitchison T, Johnson BE, Ferguson J. A comparison of narrow band phototherapy (TL-01) and photochemotherapy (PUVA) in the management of polymorphic light eruption. Br J Dermatol. 1993 Dec. 129(6):708-12. [QxMD MEDLINE Link].
Barolet D, Boucher A. LED photoprevention: reduced MED response following multiple LED exposures. Lasers Surg Med. 2008 Feb. 40(2):106-12. [QxMD MEDLINE Link].
Hadshiew IM, Treder-Conrad C, v Bülow R, et al. Polymorphous light eruption (PLE) and a new potent antioxidant and UVA-protective formulation as prophylaxis. Photodermatol Photoimmunol Photomed. 2004 Aug. 20(4):200-4. [QxMD MEDLINE Link].
Ahmed RS, Suke SG, Seth V, Jain A, Bhattacharya SN, Banerjee BD. Impact of oral vitamin E supplementation on oxidative stress & lipid peroxidation in patients with polymorphous light eruption. Indian J Med Res. 2006 Jun. 123(6):781-7. [QxMD MEDLINE Link].
Neumann R, Rappold E, Pohl-Markl H. Treatment of polymorphous light eruption with nicotinamide: a pilot study. Br J Dermatol. 1986 Jul. 115(1):77-80. [QxMD MEDLINE Link].
Eberlein-König B, Fesq H, Abeck D, Przybilla B, Placzek M, Ring J. Systemic vitamin C and vitamin E do not prevent photoprovocation test reactions in polymorphous light eruption. Photodermatol Photoimmunol Photomed. 2000 Apr. 16 (2):50-2. [QxMD MEDLINE Link].
Gruber-Wackernagel A, Bambach I, Legat FJ, et al. Randomized double-blinded placebo-controlled intra-individual trial on topical treatment with a 1,25-dihydroxyvitamin D(3) analogue in polymorphic light eruption. Br J Dermatol. 2011 Jul. 165(1):152-63. [QxMD MEDLINE Link].
Pareek A, Khopkar U, Sacchidanand S, Chandurkar N, Naik GS. Comparative study of efficacy and safety of hydroxychloroquine and chloroquine in polymorphic light eruption: a randomized, double-blind, multicentric study. Indian J Dermatol Venereol Leprol. 2008 Jan-Feb. 74 (1):18-22. [QxMD MEDLINE Link].
Jansen CT. Oral carotenoid treatment in polymorphous light eruption: a cross-over comparison with oxychloroquine and placebo. Photodermatol. 1985 Jun. 2(3):166-9. [QxMD MEDLINE Link].
Norris PG, Hawk JL. Successful treatment of severe polymorphous light eruption with azathioprine. Arch Dermatol. 1989 Oct. 125(10):1377-9. [QxMD MEDLINE Link].
Tanew A, Radakovic S, Gonzalez S, Venturini M, Calzavara-Pinton P. Oral administration of a hydrophilic extract of Polypodium leucotomos for the prevention of polymorphic light eruption. J Am Acad Dermatol. 2012 Jan. 66 (1):58-62. [QxMD MEDLINE Link].
Winkelmann RR, Del Rosso J, Rigel DS. Polypodium leucotomos extract: a status report on clinical efficacy and safety. J Drugs Dermatol. 2015 Mar. 14 (3):254-61. [QxMD MEDLINE Link].
McNeil MM, Nahhas AF, Braunberger TL, Hamzavi IH. Afamelanotide in the Treatment of Dermatologic Disease. Skin Therapy Lett. 2018 Nov. 23 (6):6-10. [QxMD MEDLINE Link].

Media Gallery

Photograph of a springtime eruption of polymorphous light eruption in a 6-year-old boy. The eruption has occurred in the spring since the patient was aged 5 years, and it resolves completely with no scarring by mid to late summer. High block sunscreens attenuate but do not prevent the eruption. No itching or pain occurs. Courtesy of Dr. Jeremy F. Harrison, FRCA, FFAEM.
Polymorphous light eruption on the thighs and hand. Courtesy of DermNet New Zealand (http://www.dermnetnz.org/assets/Uploads/reactions/pmle2.jpg).
Polymorphous light eruption on the chest. Courtesy of DermNet New Zealand (http://www.dermnetnz.org/assets/Uploads/_resampled/FitWzY0MCw0ODBd/WatermarkedWyIyNTg0MSJd/pmle-14.jpg).
Polymorphous light eruption on the chest. Courtesy of DermNet New Zealand (http://www.dermnetnz.org/assets/Uploads/_resampled/FitWzY0MCw0ODBd/WatermarkedWyIyNTg0MCJd/pmle-15.JPG).
Polymorphous light eruption on the arm. Courtesy of Waikato District Health Board and DermNet New Zealand (http://www.dermnetnz.org/assets/Uploads/_resampled/FitWzY0MCw0ODBd/WatermarkedWyIyNTg0MCJd/pmle-22.JPG).
Polymorphous light eruption pathology showing papillary dermal edema. Courtesy of DermNet New Zealand (https://www.dermnetnz.org/assets/Uploads/pathology/e/pmle-figure-1.jpg).
Polymorphous light eruption pathology showing papillary dermal edema. Courtesy of DermNet New Zealand (https://www.dermnetnz.org/assets/Uploads/pathology/e/pmle-figure-2.jpg).
Polymorphous light eruption pathology showing papillary dermal edema with lymphocytes in the epidermis (exocytosis). Courtesy of DermNet New Zealand (https://www.dermnetnz.org/assets/Uploads/pathology/e/pmle-figure-3.jpg).
Polymorphous light eruption pathology. The infiltrate is mainly lymphocytic but there may be intermixed eosinophils, neutrophils, and histiocytes. Courtesy of DermNet New Zealand (https://www.dermnetnz.org/assets/Uploads/pathology/e/pmle-figure-4.jpg).

of 9

Author

Saud A Alobaida, MBBS, FRCPC Dermatologist, Pediatric and General Dermatology, Department of Dermatology, King Faisal Specialist Hospital and Research Centre, Saudi Arabia

Saud A Alobaida, MBBS, FRCPC is a member of the following medical societies: American Academy of Dermatology

Disclosure: Nothing to disclose.

Coauthor(s)

Wingfield Rehmus, MD, MPH Dermatologist, BC Children's Hospital, Vancouver, British Columbia

Wingfield Rehmus, MD, MPH is a member of the following medical societies: American Academy of Dermatology, Society for Pediatric Dermatology

Disclosure: Serve(d) as a speaker or a member of a speakers bureau for: Abbvie; Valeant Canada Received honoraria from Valeant Canada for advisory board; Received honoraria from Pierre Fabre for advisory board; Received honoraria from Mustella for advisory board; Received honoraria from Abbvie for advisory board.

Specialty Editor Board

Richard P Vinson, MD Assistant Clinical Professor, Department of Dermatology, Texas Tech University Health Sciences Center, Paul L Foster School of Medicine; Consulting Staff, Mountain View Dermatology, PA

Richard P Vinson, MD is a member of the following medical societies: American Academy of Dermatology, Texas Medical Association, Association of Military Dermatologists, Texas Dermatological Society

Disclosure: Nothing to disclose.

Jeffrey P Callen, MD Professor of Medicine (Dermatology), Chief, Division of Dermatology, University of Louisville School of Medicine

Jeffrey P Callen, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American College of Physicians, American College of Rheumatology

Disclosure: Received income in an amount equal to or greater than $250 from: Genentech as a consultant for a potential study on a drug that has yet to be approved for any use Received honoraria from UpToDate for author/editor; Received royalty from Elsevier for book author/editor; Received dividends from trust accounts, but I do not control these accounts, and have directed our managers to divest pharmaceutical stocks as is fiscally prudent from Stock holdings in various trust accounts include some pharmaceutical companies and device makers for these trust accounts; I served on a safety monitoring committee for Principia Biopharma (ended 9-2021) for: Stocks held in various trust accounts: Allergen; Pfizer; 3M; Johnson and Johnson; Merck; Abbott Laboratories; AbbVie; Procter and Gamble; Amgen; Gilead.

Chief 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.

Additional Contributors

Craig A Elmets, MD Professor and Chair, Department of Dermatology, Director, Chemoprevention Program Director, Comprehensive Cancer Center, UAB Skin Diseases Research Center, University of Alabama at Birmingham School of Medicine

Craig A Elmets, MD is a member of the following medical societies: American Academy of Dermatology, American Association of Immunologists, American College of Physicians, American Federation for Medical Research, Society for Investigative Dermatology

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: University of Alabama at Birmingham; University of Alabama Health Services Foundation Serve(d) as a speaker or a member of a speakers bureau for: Ferndale Laboratories Received research grant from: NIH, Veterans Administration, California Grape Assn Received consulting fee from Astellas for review panel membership; Received salary from Massachusetts Medical Society for employment; Received salary from UpToDate for employment. for: Astellas.

Sophie Shirin, MD Consulting Staff, Global Dermatology

Sophie Shirin, MD is a member of the following medical societies: American Academy of Dermatology

Disclosure: Nothing to disclose.

Raul Del Rosario, MD Consulting Staff, Dermatopathology, Mission Hospital at Laguna Beach

Raul Del Rosario, MD is a member of the following medical societies: American Society for Clinical Pathology

Disclosure: Nothing to disclose.

Noah S Scheinfeld, JD, MD, FAAD † Assistant Clinical Professor, Department of Dermatology, Weil Cornell Medical College; Consulting Staff, Department of Dermatology, St Luke's Roosevelt Hospital Center, Beth Israel Medical Center, New York Eye and Ear Infirmary; Assistant Attending Dermatologist, New York Presbyterian Hospital; Assistant Attending Dermatologist, Lenox Hill Hospital, North Shore-LIJ Health System; Private Practice

Noah S Scheinfeld, JD, MD, FAAD is a member of the following medical societies: American Academy of Dermatology

Disclosure: Nothing to disclose.

Acknowledgements

The authors and editors of Medscape Reference gratefully acknowledge the contributions of previous author, Dr. Ada Winkielman, to the development and writing of this article.