Disorders of Hyperpigmentation

Disorders of Hyperpigmentation

Definitions

• Hyperpigmentation: a term used to describe disorders characterized by darkening of the skin; encompasses hypermelanosis.

• Hypermelanosis: a more specific term that denotes an increase in the melanin content of the skin; typically due to an increase in melanin production but occasionally from an increase in the density of active melanocytes.

• Discoloration: a term used to describe an abnormal color of the skin; may be due to deposition of substances such as drugs, drug complexes (e.g. with melanin or iron), or heavy metals within the dermis.

• Dyschromatosis: a disorder characterized by the presence of both hypo- and hyperpigmentation.

• Pigment incontinence: the presence of melanin within dermal macrophages (melanophages); the source of the melanin is the epidermis, and this typically results from inflammation at the dermal–epidermal junction.

• Epidermal pigmentation: denotes increased melanin within the epidermis, which typically leads to a light brown to dark brown color.

• Dermal pigmentation: denotes increased melanin in the dermis, primarily within melanophages; characteristically presents as a gray-blue to gray-brown color.

Approach to Disorders of Hyperpigmentation

• Disorders of hyperpigmentation usually result from an increase in melanin production and occasionally from an increase in the density of active melanocytes.

• The clinical approach to these disorders is simplified by dividing them into four patterns, namely circumscribed, diffuse, linear, and reticulated (Fig. 55.1).

Fig. 55.1 Approach to disorders of hyperpigmentation.

• The most common clinical pattern is circumscribed; observation of the sites of involvement, shape, configuration, and size can provide clues to the diagnosis.

• The dyschromatoses are discussed separately.

Circumscribed Hyperpigmentation

• The three major entities in this category are melasma, postinflammatory hyperpigmentation, and drug-induced hyperpigmentation.

Melasma

• A very common, acquired disorder characterized by symmetric, hyperpigmented patches with irregular borders, resulting from an increase in epidermal and/or dermal melanin; favors the face (see below) > mid-upper chest and extensor forearms.

• Seen primarily in women; increased prevalence in individuals with skin phototypes III–IV.

• Pathogenesis thought to be related to hyperfunctional melanocytes that are stimulated by exacerbating factors, such as sun exposure and hormones (e.g. pregnancy, oral contraceptives).

• Three classic clinical patterns based on distribution: centrofacial (most common), malar, and mandibular (Fig. 55.2).

Fig. 55.2 Various forms of melasma and melasma-like hyperpigmentation. A Malar variant. B Mild centrofacial type with sparing of the philtrum. C Extension of the hyperpigmentation onto the mandible. D Involvement of the extensor forearm; note the same irregular outline as seen on the face. E Melasma-like appearance in a patient with previous acute cutaneous lupus erythematosus. C–E, Courtesy, Jean L. Bolognia, MD.

• Classically, melasma was also classified based on findings from Wood’s lamp examination: lesions that enhance imply an increase in epidermal melanin and lesions that do not enhance imply an increase in dermal melanin; however, mixed epidermal and dermal melasma patterns are common.

• In northern latitudes, lesions tend to fade during the winter months; melasma tends to be more persistent in darkly pigmented individuals.

• DDx: postinflammatory hyperpigmentation, drug-induced (e.g. minocycline, amiodarone), acquired bilateral nevus of Ota-like macules (especially in Asian women), actinic lichen planus, pigmented contact dermatitis, exogenous ochronosis due to the application of hydroquinone-containing bleaching agents, erythromelanosis faciei.

• These other disorders are distinguished from melasma based on historical aspects (e.g. drug ingestion, application of topical medications or cosmetics, previous inflammation), color (e.g. clusters of nevus of Ota-like macules are typically blue-gray in color), distribution pattern, histologic features, and primary lesions, if present.

• Treatment options are outlined in Table 55.1; typically epidermal hyperpigmentation responds best to treatment.

Table 55.1

Suggested treatment options for melasma.

^* Results from topical treatments may take up to 6 months to appreciate; depending on the patient, HQ and combination HQ + retinoid + CS are typically used daily for 2–4 months and then decreased in frequency to 1–2 times per week; prolonged daily use can result in side effects such as perioral dermatitis, telangiectasias, and atrophy (CS) and ochronosis (HQ).

^** While topical HQ can cause an allergic contact dermatitis, all topical agents may cause an irritant contact dermatitis, which can result in worsening of the dyspigmentation; if this is a concern, a small, nonfacial site test can be performed prior to widespread facial application.

^† Typically a Class 5–7 topical CS is used (see Appendix).

^‡ Potential risk of post-procedural dyspigmentation; a site test should be performed prior to widespread facial laser or light therapy.

HQ, hydroquinone.

Drug-Induced Circumscribed Hyperpigmentation and Discoloration

• A wide range of medications and chemicals can cause hyperpigmentation or discoloration in circumscribed, diffuse, and even linear patterns; longitudinal or horizontal melanonychia may also be present.

• The most common culprits of drug-induced circumscribed hyperpigmentation and discoloration are minocycline and the antimalarials (Table 55.2; Figs. 55.3–55.6).

Fig. 55.3 Gray-violet discoloration of the face due to amiodarone. Note the sparing of the lower eyelid. Courtesy, Jean L. Bolognia, MD.

Fig. 55.4 Blue-violet discoloration of previous leprosy lesions in a patient treated with clofazimine. Courtesy, Anne Burdick, MD.

Fig. 55.5 Exogenous ochronosis secondary to topical hydroquinone. This cause of progressive darkening is seen more commonly in Africa. Courtesy, Regional Dermatology Training Centre, Moshi, Tanzania.

Fig. 55.6 Minocycline-induced discoloration. A The distribution on the shins and the gray-blue color can be similar to that seen with antimalarials. B Sometimes the discoloration is misdiagnosed as ecchymoses, but the subsequent color changes of green and yellow do not occur. C Blue-black pigmentation within acne scars and inflammatory papules. A, Courtesy, Mary Wu Chang, MD; C, Courtesy, Richard Antaya, MD.

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Apr 22, 2016 | Posted by admin in Dermatology | Comments Off

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