Background
Idiopathic guttate hypomelanosis (IGH) is an acquired, benign leukoderma of unknown etiology. Idiopathic guttate hypomelanosis is most commonly a complaint of middle-aged, light-skinned women, but it is increasingly seen in both sexes and older dark-skinned people with a history of long-term sun exposure. See the image below.
View Image | Idiopathic guttate hypomelanosis. Courtesy of DermNet New Zealand (http://www.dermnetnz.org/assets/Uploads/colour/igh1.jpg). |
Idiopathic guttate hypomelanosis is a benign condition. The cause is not known, but it appears to be related to the effect of the sun on melanocytes, which makes them effete.
A variety of therapeutic methods, including topical steroids, topical retinoids, dermabrasion, cryotherapy, and minigrafting, have been used for idiopathic guttate hypomelanosis with variable success.[1]
Pathophysiology
Because pigmentation of the skin is due to an integration of melanocyte and keratinocyte function, an acquired defect of the epidermal melanin unit results in the observed hypopigmentation in idiopathic guttate hypomelanosis patients. Significantly fewer dopa oxidase-positive, KIT+, and melanocytes are seen in the lesions.[2, 3] In 1967, Hamada and Saito found a 50% reduction in melanocytes.
Epidemiology
Frequency
United States
Idiopathic guttate hypomelanosis is a very common condition to the point of being almost universal in elderly fair-skinned individuals. In 2002, a case control study of 47 renal transplant patients demonstrated a significant positive association between HLA-DQ3 and the development of idiopathic guttate hypomelanosis and a significant negative association between HLA-DR8 and the development of idiopathic guttate hypomelanosis.
International
Idiopathic guttate hypomelanosis is most common in countries with fair-skinned populations having a high degree of sun exposure.
Race
Idiopathic guttate hypomelanosis affects fair-skinned people at a younger age.
Sex
Idiopathic guttate hypomelanosis is seen far more frequently in women, beginning around the age of 30 years. However, with increasing age and sun exposure, it is found almost equally in elderly men and women. Why idiopathic guttate hypomelanosis occurs earlier in young women than in young men is unknown.
Age
Idiopathic guttate hypomelanosis is related to the lack of pigmentary protection from the sun and sun exposure rather than to age. Fair-skinned women develop this condition first; later, with increasing age and exposure to sun, both sexes seem to be equally affected.
Prognosis
Idiopathic guttate hypomelanosis is cosmetic alone, albeit, it is indicative of cumulative sun exposure. Idiopathic guttate hypomelanosis progresses with increasing sun exposure and, to a lesser degree, with age.
Patient Education
Progress in preventing idiopathic guttate hypomelanosis can be made by educating young women not to tan their legs.
History
Typically, idiopathic guttate hypomelanosis develops first on the legs of fair-skinned women in early adult life. Later, it may spread to other sun-exposed areas, such as the arms and the upper part of the back. The face is inexplicably not involved early in idiopathic guttate hypomelanosis. A familial tendency to develop idiopathic guttate hypomelanosis has been noted.[4]
Physical Examination
Idiopathic guttate hypomelanosis consists of discrete, angular or circular macules that are 1-3 mm in diameter. However, lesions may measure up to 10 mm in diameter. These lighter-than-normal skin macules are off white, hypopigmented, or achromic. They are often noted first on the anterior aspects of the legs. Later, they appear on the forearms. The distribution seems to be photo related, except for the face, which is affected later than the limbs.
Causes
The exact cause of idiopathic guttate hypomelanosis is not agreed upon; however, it is hypothesized that ultraviolet light plays an important role.[5]
Laboratory Studies
Idiopathic guttate hypomelanosis should be diagnosed on clinical grounds. A Wood light examination could be helpful in revealing unsuspected involvement. Dopa staining can be useful because dopa-positive melanocytes are decreased.
Procedures
In atypical cases of idiopathic guttate hypomelanosis, a biopsy may be indicated. Dermatoscopic examination may aid in diagnosis. Peripheral lesion findings include amoeboid, featherlike, and petaloid patterns described in lesions of idiopathic guttate hypomelanosis.[8, 9]
Histologic Findings
Several light and electron microscopic studies have revealed a characteristic pathologic picture for idiopathic guttate hypomelanosis. Typical histologic findings are epidermal atrophy of the actinic type, a patchy decrease or absence of melanocytes and melanin, flat rete ridges, and basket weave hyperkeratosis. Skip areas of retained melanin can help histologically differentiate this condition from other disorders of pigmentation.[10]
Medical Care
Medical therapy for idiopathic guttate hypomelanosis includes corticosteroids, either topical or intralesional, and retinoids, typically topical tretinoin.[11] One report describes successful treatment with pimecrolimus 1%[6] ; however, caution is warranted because the author has anecdotal experience possibly suggesting that topical calcineurin inhibitors may be linked to the development of idiopathic guttate hypomelanosis in immunosuppressed patients. Another described successful treatment with topical tacrolimus, but results were not statistically significant after clinical assessments.[12]
Surgical Care
Surgical techniques, from cryosurgery to dermabrasion, have been tried for idiopathic guttate hypomelanosis, with some success.[1] Theoretically, cryotherapy would remove the damaged melanocytes, which would encourage normal melanocytes to replace them. A randomized, controlled, evaluator-blinded study of 101 lesions treated with a single 5-second tip cryotherapy treatment demonstrated 82.3% of the lesions improved by 75% at 4 months.[13] Fractional carbon dioxide laser and nonablative fractional photothermolysis treatment have been reported as safe and effective.[14, 15, 16] Excimer laser also may be safe and effective using the vitiligo protocol.[17] The use of a spot 88% phenol peel is another option; however, persistent scabbing and hyperpigmentation are potential adverse effects.[18]
Consultations
In doubtful cases, a consultation with a dermatologist should precede any laboratory or biopsy studies.
Prevention
Idiopathic guttate hypomelanosis may be avoided, at least until late in life, by protection against sun damage.
Avoiding sun tanning is an important adjunct to prevention of idiopathic guttate hypomelanosis because tanning accentuates the process and intensifies the pigmentary contrast. Artificial tanning using dihydroxyacetone-containing topical agents is a good alternative.
One report suggests that patients in the study who used “body scrubbers” had an increased likelihood having idiopathic guttate hypomelanosis lesions.[19]
Long-Term Monitoring
Sunscreens are advised because idiopathic guttate hypomelanosis is a marker of sun damage.
Medication Summary
The goals of pharmacotherapy for idiopathic guttate hypomelanosis are to reduce morbidity and to prevent complications.
Tretinoin topical (Avita, Retin-A)
Clinical Context:
Tretinoin has been shown to reverse some aspects of sun damage. It is available as 0.025%, 0.05%, and 0.1% creams and as 0.01% and 0.025% gels.
Class Summary
Although tretinoin has been used with some success, avoiding ultraviolet-induced pigmentation and an artificial coloration of the area is recommended as first-line therapy.
This drug is chosen perhaps because of its action in other actinic conditions.
Author
Christopher R Gorman, MD, Dermatologist, McGuire VA Medical Center
Disclosure: Nothing to disclose.
Specialty Editors
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
Disclosure: Nothing to disclose.
Chief Editor
William D James, MD, Paul R Gross Professor of Dermatology, Vice-Chairman, Residency Program Director, Department of Dermatology, University of Pennsylvania School of Medicine
Disclosure: Received income in an amount equal to or greater than $250 from: Elsevier; WebMD.
Additional Contributors
Daniel Mark Siegel, MD, MS, Clinical Professor of Dermatology, Department of Dermatology, State University of New York Downstate Medical Center
Disclosure: Nothing to disclose.
Acknowledgements
Acknowledgments
Medscape Drugs & Diseases wishes to recognize Stephen W White, MD† for his original contributions to this article.
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