Are You Confident of the Diagnosis?
Characteristic findings on physical examinatiion
Idiopathic guttate hypomelanosis (IGH) is a common benign acquired condition that presents as small irregularly-shaped, well-defined hypopigmented porcelain white macules, predominantly on shins and forearm (Figure 1). The surface is smooth, without atrophy. Usually, the trunk and face are spared. Once present, lesions do not change in size.
Expected results of diagnostic studies
Histology reveals flattening of rete ridges at the dermal-epidermal junction, moderate to marked reduction of melanin granules in the basal and suprabasal layers, basket-weave hyperkeratosis, and a reduced number of DOPA-positive epidermal melanocytes.
Diagnosis is clinical. The differential diagnosis incljudes achromic verruca plana, pityriasis lichenoides chronica, disseminated hypopigmented keratoses following psolalen plus ultraviolet A (PUVA) therapy, and confetti-like lesions of tuberous sclerosis.
Who is at Risk for Developing this Disease?
AGH is more common above the age of 40 and the prevalence increases with age; however, IGH may occur in young adults. Women are more frequently affected than men.
What is the Cause of the Disease?
The exact etiology is unknown. Possible causes include genetic factors like HLA-DQ3, chronic sun exposure, phototherapy, trauma, and autoimmunity.
Systemic Implications and Complications
No systemic implications or complications are associated with this condition.
Treatment options are limited (Table I) and optimal treatment mostly entails observation and photoprotection.
|Broad spectrum sunscreens|
|Topical tretinoin cream|
|Topical pimecrolimus 1%|
|Surgical and physical modalities|
|Carbon dioxide laser|
|Chemical peel (phenol and trichloroacetic acid)|
Optimal Therapeutic Approach for this Disease
Treatment for IGH is limited. Most treatments are anecdotal without any randomized controlled clinical trials. A conservative approach with observation and photoprotection may prevent development of new lesions.
Tretinoin cream used daily for 4 months showed some improvement in pigmentation in one study. In this study 0.025% tretinoin cream was used nightly for the first week, 0.05% nightly for the second week, and 0.1% nightly for the remainder of the study. Pimecrolimus 1% cream applied twice daily for 16 weeks demonstrated some improvement in pigmentation in another small study.
Cryotherapy has been reported to be useful in treating IGH. In one study, treated lesions showed repigmentation in 6-8 weeks and histologically demonstrated more DOPA-positive melanocytes than untreated lesions, but less than normal skin. Another small study, reported that treatment with local superficial dermabrasion caused repigmentation in 80% of treated patients. Carbon dioxide laser and superficial chemical peels have been tried as treatment options without much success.
In addition, cover-up make up and concealers made by brands such as Dermablend can be used to mask the hypopigmented macules.
Patients should be advised that treatment options are limited and results are mixed. Photoprotection can help prevent development of new lesions. If treatment with cryotherapy is being considered, patients should be counseled regarding the risk of hypopigmentation post-treatment. Also, if a patient has a history of hypertrophic scars or keloids, a test site site should be done before treatment of all lesions with superficial dermabrasion.
Unusual Clinical Scenarios to Consider in Patient Management
No unusual clinical scenarios arise in treating patients with idiopathic guttate hypomelanosis. Although facial involvement is considered rare, a recent study documented IGH in 6% of patients with the disorder.
What is the Evidence?
Asawanonda, P, Sutthipong, T, Prejawai, N. “Pimecrolimus for idiopathic guttate hypomelanosis”. J Drugs Dermatol. vol. 9. 2010. pp. 238-9. (Small study from Thailand of four patients with IGH. Lesions on one arm were treated with 1% pimecrolimus cream twice daily for 16 weeks, while those on other arm were left untreated. In three cases, 25-75% improvement in pigmentation was noted by both physician evaluators and patients. First noticeable improvement was noted at 8 weeks. No improvement noted in one patient.)
Pagnoni, A, Kligman, A, Sadiq, I, Stoudemayer, T. “Hypopigmented macules of photodamaged skin and their treatment with topical tretinoin”. Acta Derm Venreol. vol. 79. 1999. pp. 305-10. (Four patients (three with macular hypomelanosis and one with idiopathic guttate hypomelanosis), part of a larger study of 40 patients comparing these entities, were treated with tretinoin cream 0.025% nightly for 1 week, then 0.05% nightly for 1 week, and finally 0.1% nightly for the remaining 3.5 months on one forearm, while the other was untreated. At the end of the study, treated lesions showed improved pigmentation, restored elasticity, and glyphic markings.)
Hexsel, D. “Treatment of idiopathic guttate hypomelanosis by localized superficial dermabrasion”. Dermatol Surg. vol. 25. 1999. pp. 917-8. (Twenty female patients treated with local dermabrasion using a standard dermabrader with small diamond fraises with abrasion speed between 10,000 to 15,000 rpm. Treated area is exposed to sunlight after the procedure. Eighty percent of patients noted repigmentation of lesions.)
Ploysangam, T, Dee-Ananlap, S, Suvanprakorn, P. “Treatment of IGH with liquid nitrogen: light and electron microscopic studies”. J Am Acad Dermatol. vol. 23. 1990. pp. 681-4. (Histologic analyses of lesions of IGH from 26 patients and from normal skin of 26 age-matched controls was performed. Ten patients with IGH were treated withcryotherapy for 10 seconds. Eighty-seven lesions were treated, of which 79 developed complete repigmentation in 6 to 8 weeks.)
Ortonne, J, Bolognia, JL, Jorizzo, JL, Rapini, RP. “Vitiligo and other disorders of hypopigmentation”. Dermatology. 2008. pp. 913-39. (Section in book chapter that reviews the clinical presentation, histopathology, and some treatment options for IGH.)
Shin, M-K, Jeong, K-H, Oh, I-H, Choe, B-K. “Clinical features of idiopathic guttate hypomelanosis in 646 subjects as association with other aspects of photoaging”. Int J Dermatol. vol. 50. 2011. pp. 798-805. (This is a study of 646 patients with IGH detailing the clinical features. Interestingly, 6% of patients were found to have facial lesions, with 93% having lesions on the distal lewer extremities. The authors concluded that this is related to aging of the skin, possibly caused by “microtrauma.”)
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