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Chapter 75. Hypomelanoses and Hypermelanoses

Hilde Lapeere; Barbara Boone; Sofie De Schepper; Evelien Verhaeghe; Mireille Van Geel; Katia Ongenae; Nanja Van Geel; Jo Lambert; Lieve Brochez

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Hypomelanoses and Hypermelanoses at a Glance
  • Pigmentation disorders confront the clinician with a sometimes complex differential diagnosis, but can be approached logically as follows:
    • Congenital or acquired
    • Isolated or part of a syndrome
    • Diffuse or circumscribed
    • Epidermal or dermal
    • With or without inflammation
  • Altered skin pigmentation may be caused by the following factors:
    • Increased or decreased melanin
    • Abnormal melanin distribution
    • Decreased hemoglobin
    • Deposition of exogenous pigments

Pigmentation disorders of the skin can either be hypomelanotic, hypermelanotic, or may present with a pattern of mixed hypo- and hypermelanosis. The diagnosis of these disorders can be quite challenging. An algorithmic approach based on clinical features and history of pigmentary disorders is used throughout this chapter and serves as a guide for the clinician’ diagnosis and treatment (eFigs. 75-0.1 and 75-0.2) (Table 75-1, eTable 75-1.1).

Table 75-1 Differential Diagnosis and Management of Dermal Melanocytosis
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Table 75-1 Differential Diagnosis and Management of Dermal Melanocytosis

Nevus of Ota

Nevus of Ito

Mongolian Spot

Nevus of Hori

Dermal Melanocyte Hamartoma

Epidemiology

• Mostly congenital

• Sporadic (rare familial cases)

• Asian and female predominance

• Mostly congenital

• Sporadic (rare familial cases)

• Asian and female predominance

• Congenital

• Often familial

• Asian, African, and Hispanic population with slight male predominance

• Acquired

• Familial or sporadic

• Asian and female predominance

• Congenital

Clinical presentation

• Blue to slate-gray mottled macular hyperpigmentation

• Blue to slate-gray mottled macular hyperpigmentation

• Uniform blue to slate-gray macular hyperpigmentation

• Brown–blue progressing to slate-gray mottled macular hyperpigmentation

• Mottled hyperpigmentation with small blue–gray macules in a diffuse pigmented patch

Distribution

• Trigeminal nerve

• Acromioclavicular nerve

• Lower back and sacrum

• Especially malar region of the cheek (also forehead, upper eyelids, temple)

• Dermatomal distribution

Histology

• Spindle-shaped melanocytes diffusely throughout the dermal layers. Sometimes more band-like melanocytic proliferation and stromal fibrotic reaction.

• Spindle-shaped melanocytes diffusely throughout the dermal layers. Sometimes more band-like melanocytic proliferation and stromal fibrotic reaction

• Spindle-shaped melanocytes diffusely throughout the dermal layers

• Dermal melanocytes in the upper and middermis

• Dermal melanocytes in the upper two-thirds of the dermis (including subpapillary layer)

Therapy

• Q-switched laser

• Cryotherapy

• Surgery

• Q-switched laser

• Cryotherapy

• Surgery

• Usually spontaneous regression during childhood

• Q-switched laser in combination with bleaching cream and chemical peels

• None

Associated features

• Rare malignant transformation

• No associated features of medical concern

• Possible association with inborn errors of metabolism

• No associated features of medical concern

• None

eFigure 75-0.1
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Algorithm for the diagnostic approach to hypomelanosis.

eFigure 75-0.2
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Algorithm for the diagnostic approach to hypermelanosis. CALM = café-au-lait macule; LEOPARD syndrome = lentigines; electrocardiogram conduction defects; ocular hypertelorism; pulmonary stenosis; ...

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