Chemical-Associated Vitiligo

Abstract

An otherwise healthy man in his 40s presented with white macules and patches that appeared on his skin several years ago. Initially, he noticed asymptomatic white discoloration on the ventral aspect of wrists, with subsequent involvement of thehead and neck. He had no relevant medical, drug, or family history, except for thyroid dysfunction in his mother. He worked in a laundry facility, with frequent exposure to detergents. Examination revealed well-demarcated hypopigmented patches without erythema or scaling on the ventral forearms (Figure 1). One patch on the occipital area scalp showed white discoloration of the associated hair (Figure 2). Wood's lamp examination showed no accentuation. Based on the patient’s history of exposure by frequently implicated chemicals, as well as the morphology and distribution of skin lesions, a diagnosis of chemical-associated vitiligo was made.Figure 2Well-defined coalescing hypopigmented patches on ventral forearm.View Large Image Figure ViewerDownload Hi-res image Download (PPT) Chemical-associated vitiligo, an acquired disorder that presents with hypo- or depigmented patches, is thought to be induced by repeated exposure to specific chemicals.1Harris J.E. Chemical-induced vitiligo.Dermatol Clin. 2017; 35: 151-161Abstract Full Text Full Text PDF PubMed Scopus (55) Google Scholar Several chemical compounds have been implicated, most of which contain phenol groups in their chemical structure. Because the phenol group constitutes a part of the amino acid tyrosine, the precursor of melanin, it has been hypothesized that phenol-containing compounds act as tyrosine analogs when applied to the skin, thereby interfering with melanogenesis.1Harris J.E. Chemical-induced vitiligo.Dermatol Clin. 2017; 35: 151-161Abstract Full Text Full Text PDF PubMed Scopus (55) Google Scholar Others have hypothesized that depigmenting chemicals produce metabolites that are toxic to melanocytes or overwhelm the melanocyte ability to withstand oxidative stress.2Boissy R.E. Manga P. On the etiology of contact/occupational vitiligo.Pigment Cell Res. 2004; 17: 208-214Crossref PubMed Scopus (207) Google Scholar In cases of occupational exposure, as in our patient, the hands and forearms are frequently involved. However, some reports demonstrated that lesions could appear in remote areas: that is, those not in direct contact with chemical substances.3Bonamonte D. Vestita M. Romita P. Filoni A. Foti C. Angelini G. Chemical leukoderma. dermatitis: contact, atopic, occupational, drug.Dermatitis. 2016; 27: 90-99Crossref PubMed Scopus (16) Google Scholar This observation has led to invocation of the autoimmune theory, proposing that chemical-induced stress in melanocytes initiates an autoimmune response, leading to their destruction. Subsequently, this immune response can affect other melanocytes in distant regions that are not directly in contact with the chemical.1Harris J.E. Chemical-induced vitiligo.Dermatol Clin. 2017; 35: 151-161Abstract Full Text Full Text PDF PubMed Scopus (55) Google Scholar By contrast, idiopathic vitiligo commonly affects the periorificial areas, nipples, and genitals. Chemical-associated vitiligo represents a diagnostic challenge, as it is often difficult to differentiate it from idiopathic vitiligo based on the clinical as well as the histopathological presentation.1Harris J.E. Chemical-induced vitiligo.Dermatol Clin. 2017; 35: 151-161Abstract Full Text Full Text PDF PubMed Scopus (55) Google Scholar The presence of 3 out of the following 4 criteria are considered sufficient for establishing the diagnosis of chemical-associated vitiligo: acquired vitiligo-like depigmented lesion(s), history of repeated exposure to specific chemical compounds, patterned vitiligo-like macules at site of exposure, and confetti macules.4Ghosh S. Mukhopadhyay S. Chemical leucoderma: a clinico-aetiological study of 864 cases in the perspective of a developing country.Brit J Dermatol. 2009; 160: 40-47Crossref PubMed Scopus (69) Google Scholar Thorough history taking is essential to diagnose chemical-associated vitiligo and identify the possible culprit. Presumably, chemical-associated vitiligo does not confer the same increase in associated autoimmune conditions as does idiopathic vitiligo, although this is not well studied.5Gill L. Zarbo A. Isedeh P. Jacobsen G. Lim H.W. Hamzavi I. Comorbid autoimmune diseases in patients with vitiligo: a cross-sectional study.J Am Acad Dermatol. 2016; 74: 295-302Abstract Full Text Full Text PDF PubMed Scopus (89) Google Scholar In many cases, strict avoidance of the offending chemical agent allows the condition to self-resolve. Moreover, chemical-associated vitiligo tends to respond better to skin-directed treatments than idiopathic vitiligo.1Harris J.E. Chemical-induced vitiligo.Dermatol Clin. 2017; 35: 151-161Abstract Full Text Full Text PDF PubMed Scopus (55) Google Scholar