Darkened skin


  • Case #1


    Case #1

  • Case #2


    Case #2

Case #1

A 45-year-old Hispanic woman presents with a 2-year history of darkened skin on her face and neck. She states the darker areas started out as small patches on her cheeks and extended to her forehead and neck. A few of her family members have a similar rash. She has occasional mild pruritus and denies any other symptoms. The patient is frequently in the sun and rarely wears sun protection. She had a history of hypertension and hyperlipidemia. Her medications include fenofibrate and metoprolol. She is interested in lightening creams for the darker areas.

Case #2

An 18-year-old Hispanic woman presents with a 5-year history of darkened skin on her arm. She denies any pruritus or pain in the area but is bothered by the location of the lesion. The patient states the area had had increased hair growth in the past few years. She has not tried to treat the lesion. She is otherwise healthy and takes no medications. Her mother says she does not recall seeing a “birthmark” at birth.

Case #1First described in 1974, lichen planus pigmentosus (LPP) is an uncommon macular variant of cutaneous lichen planus (LP).1 LPP is characterized by the insidious onset of small, ill-defined, oval-to-round macules that merge to form large areas of hyperpigmentation over...

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Case #1

First described in 1974, lichen planus pigmentosus (LPP) is an uncommon macular variant of cutaneous lichen planus (LP).1 LPP is characterized by the insidious onset of small, ill-defined, oval-to-round macules that merge to form large areas of hyperpigmentation over time.2 Pigmentation among individuals varies from slate grey to brownish-black, but in a single patient, LPP is relatively uniform in color.2

Diffuse hyperpigmentation is the most common clinical pattern of LPP, but reticular, zosteriform, blaschkoid, perifollicular, generalized, and linear patterns have also been reported.3-6 LPP lesions tend to be bilaterally symmetrical and affect flexural areas and sun-exposed regions, with the head and neck being the most frequent sites of involvement, followed by the trunk and upper and lower limbs.2 The forehead and preauricular region (including the temples) tend to be the first sites of presentation and are affected in the majority of patients. Widespread involvement can occur, with approximately 30% of patients exhibiting over 10% body surface area involvement, though the palms, soles, nails, and usually, oral mucosa are spared.2 LPP with predominant localization of the disease in intertriginous areas, mainly the axillae, is referred to as LPP inversus.7

LPP tends to appear in the third or fourth decade of life; men have an earlier onset than women by a decade. The disease displays a slight predilection in women and is more commonly encountered in darker-skinned individuals.5

LPP has a chronic course with relapses and remissions. With time, new lesions may appear and existing lesions may enlarge slowly at the periphery and deepen in color. The duration of LPP ranges from months to years; approximately 50% of patients have the disease for 6 months to 3 years.2 In approximately 25% of patients, LPP lesions are accompanied by lesions of classical lichen planus, which are described by the “Six Ps”: planar, purple, polygonal, pruritic, papules, and plaques.

The characteristic histopathologic features of LPP include atrophy of the epidermis with loss of rete ridges, vacuolar degeneration of the basal cell layer, perivascular or lichenoid infiltrate, and dermal melanophages.2,4 Based on these histopathologic alterations, it is suspected that LPP represents a type of lichenoid tissue reaction to an unknown antigen or stimulus. LPP may have a similar pathogenesis to LP, for which there is evidence of a cytotoxic immune reaction against basal-layer keratinocytes. Although the etiology of LPP remains elusive, various factors, including topical mustard oil and amla oil, henna, hair dyes, hepatitis C virus infection, and sunlight exposure, have been proposed as triggering agents.2,3 LPP has also been reported in association with head and neck cancer and with concurrent acrokeratosis paraneoplastica.8

Treatment of LPP is often unsatisfactory, as there is no reliable, effective treatment currently available. Hydroquinone, local and systemic corticosteroids, retinoids, dimethyl sulfoxide, keratolytics, chloroquine, and immunomodulators have been used with inconsistent results. When applied twice daily for an average of 12 weeks, topical tacrolimus, a calcineurin inhibitor, lightened LPP lesions in seven of 13 patients in one prospective study and is therefore used in the treatment of some patients.4 Recently, low-fluence Q-switched neodymium-doped yttrium aluminum garnet (QS-Nd:YAG) laser therapy successfully cleared one case of LPP on the cheeks that was recalcitrant to several topical treatments and cleared one case of LPP on the forehead in combination with topical tacrolimus.9,10 Intense pulsed light (IPL) was also used to successfully treat a case of LPP that was associated with classical LP and resisted treatment with hydroquinone, glycolic acid, corticosteroids, and sunscreen.11 However, due to the scarcity of research on IPL and laser therapy for LPP, topical agents remain the mainstay of therapy for LPP.

LPP lesions tend to be asymptomatic, but approximately one-third of patients report mild pruritus and/or a burning sensation.2 Some patients also report photosensitivity. The primary concern regarding LPP, however, stems from the disease’s cosmetic burden, long clinical course, and poor response to treatment, leading to psychologic trauma and frustration.

The differential diagnosis of LPP includes erythema dyschromicum perstans (EDP, also known as ashy dermatosis), melasma, Riehl melanosis, Addison disease, fixed drug eruption, Becker nevus (BN), and postinflammatory pigmentation.

The main entity in the differential diagnosis of LPP is EDP, as the two diseases share numerous clinical and histopathologic features. However, early EDP lesions often have an inflammatory phase, in which a thin erythematous border surrounds the hyperpigmented macules and patches, whereas LPP lesions are not associated with an inflammatory phase.12 Furthermore, melanin deposition is located in the superficial dermis in LPP lesions, but it is located in the deeper dermis in EDP lesions.12

Both BN and LPP can manifest with hyperpigmented patches, but BN lesions can be distinguished by their earlier age of presentation (second decade rather than third or fourth decade of life) and frequently associated hypertrichosis. Furthermore, LPP presents with numerous lesions that often have a grey tint, whereas a BN patch is usually solitary and tan or brown in color.

In our case, a 4-mm punch biopsy was performed, confirming LPP. The patient was prescribed a mild topical steroid cream twice daily and sun protection. After 3 months of this regimen, her hyperpigmentation was unchanged, but her pruritus had improved.

Case #2

Becker nevus (BN), also known as Becker melanosis, Becker pigmentary hamartoma, and pigmented hairy epidermal nevus, is a relatively common cutaneous hamartoma that presents more frequently in men, with a male-to-female ratio ranging from 2:1 to 6:1.13,14

Few studies have reported the prevalence of BN, but in a survey of 19,302 adolescent boys and men age 17 to 26 years in France, the prevalence was 0.52%,13 and in a study of 5,837 young Italian men, the prevalence was 2.1%.15 Occurrence of BN is usually sporadic but occasionally shows familial aggregation, suggesting a paradominant mode of inheritance in which BN is only manifested clinically by a regional loss of heterozygosity.16

BN tends to present during the second decade of life as an isolated, unilateral, flat, hyperpigmented patch that enlarges gradually and may become slightly raised. The most common sites of presentation are the shoulder, arm, upper chest, and back; nearly all patients have upper trunk involvement.17 Hypertrichosis may develop after hyperpigmentation, especially in older men, and, over time, the hairs become coarser and darker.17 The lesion has a sharply demarcated and irregular border and is surrounded by small peripheral islets of affected skin that can fuse with the primary lesion. BN lesions range in color from light tan to dark brown and can measure from a few centimeters in diameter to palm-size or larger. Adolescents may develop acne within the BN, which is likely attributable to heightened local androgen sensitivity.18

Histopathologically, BN is characterized by epidermal changes with melanotic hyperpigmentation of the basal cell layer and variable presence of dermal smooth muscle hamartoma. Acanthosis, papillomatosis, keratotic plugging, and rete ridge elongation, flattening, and fusion are common histopathologic findings.19

Increased expression of androgen receptors has been reported in lesional skin, bolstering support for the theory that androgens play a pathogenic role in BN.20 An androgenic basis for the development of BN also explains the disease’s more frequent diagnosis in men, increased prominence after puberty, and histologic findings of acanthosis, dermal thickening, acne, hirsutism, and smooth muscle bundles.20 In women, diagnosis of BN may be overlooked, as the lesion often presents with less intense pigmentation and mild or absent hypertrichosis. Because BN is less conspicuous in women, the true sex ratio may be closer to 1:1.21

Most BN lesions occur as isolated cutaneous defects, but there is systemic involvement in approximately 5% of patients.22 In 1997, the term Becker nevus syndrome (BNS) was coined to describe the simultaneous occurrence of BN and ipsilateral mammary hypoplasia or other cutaneous, muscular, or skeletal defects, including scoliosis, spina bifida, and limb asymmetry.21 As a result, all patients with BN should be screened for bone, muscle, breast, and other associated abnormalities of BNS.

Because most BN lesions are benign and asymptomatic, treatment is not necessary for the majority of patients. However, therapeutic intervention is often desired by patients as the disease can be a distressing cosmetic handicap. Therapy requested by patients, therefore, has two major goals: (1) to reduce the hyperpigmentation, and (2) to reduce hypertrichosis.

Reduction of hyperpigmentation can be accomplished with a variety of laser treatments, including the erbium-doped yttrium aluminum garnet (Er:YAG) laser, Q-switched (QS-) ruby laser, Q-switched neodymium-doped yttrium aluminum garnet (QS-Nd:YAG) laser, frequency-doubled QS-Nd:YAG laser, QS long-pulse alexandrite laser, and fractional resurfacing with 1550-nm Er fiber laser. In a comparative study between Er:YAG and QS-Nd:YAG, a single pass with an Er:YAG laser decreased pigmentation of BN lesions better than three treatment sessions with the QS-Nd:YAG laser.23 In a study to test the efficacy of the long-pulse alexandrite laser, two of 11 patients had greater than 75% pigment clearance, five had 50% to 75% clearance, and four had 25% to 50% clearance.24

A case report of two patients treated by fractional resurfacing, a newer treatment modality, showed that five to six treatment sessions at 4-week intervals reduced pigment by more than 75% in 1 month.25 Unfortunately, despite the existence of many treatment modalities, recurrence rates of BN are high and postinflammatory hyperpigmentation can occur.

Shaving or trimming of excess hair can offer temporary relief from hypertrichosis, but treatment of BN with ruby laser in the normal or long-pulsed mode can provide a longer-lasting solution. Use of high-repetition-rate diode lasers is another therapeutic modality that was proposed in a recent study to treat hypertrichosis of BN lesions. In this study, 15 patients with BN underwent eight sessions of hair removal with low-fluence, high repetition-rate diode laser therapy (808-810 nm); when hair clearance was quantified at 6 and 12 months, all patients had significant hair reduction with no adverse events.26 Electrolysis is another well-established method of epilation, but its use in the removal of hair from BN has not been reported.

Without treatment, BN can persist indefinitely. Standard acne treatments should be used for patients presenting with intralesional acne. Patients should be advised to avoid direct sunlight, as sun exposure can deepen the pigmentation of lesional skin.

The principal entities that mimic BN are congenital melanocytic nevus, postinflammatory hyperpigmentation, lichen planus, café-au-lait macule, and nevus spilus. The diagnosis of BN can usually be made based on clinical appearance. Clinical findings most suggestive of BN include the presence of a single, brown, irregular patch of skin with relatively uniform color on the upper trunk, peripheral islets of hyperpigmented skin, intralesional hair and acne, and onset during childhood or adolescence with increased prominence after puberty. Clinical findings that disfavor the diagnosis of BN include pruritus or pain, scaliness, smooth borders, multiple lesions, onset in late life, variation in color, and rapid growth. In diagnostically uncertain cases, BN can be distinguished histologically by basal hyperpigmentation, papillomatosis, elongated rete ridges, acanthosis, keratotic plugging, and hamartomatous features.

In our case, biopsy was consistent with BN. The patient was reassured of the harmless nature of BN, and education was provided.

Table. Lichen planus pigmentosus vs. Becker nevus

Click to enlarge.

Kate Travis, BA, is a medical student and Rana Mays, MD, is a dermatology resident at Baylor College of Medicine in Houston.


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