Learning Objective

Describe the types, causes, and clinical features of pigmentation disorders in humans.

Pigmentation disorders involve alterations in skin, hair, or mucosal color due to changes in melanin production, distribution, or destruction of melanocytes. They can be hyperpigmentation (increased pigmentation) or hypopigmentation/depigmentation (decreased or absent pigmentation).

Hyperpigmentation

Causes:

Excess melanin production, chronic sun exposure, hormonal changes, inflammation, or genetic disorders.

Examples:

• Melasma (facial hyperpigmentation, often hormonal)
• Post-inflammatory hyperpigmentation (after trauma or inflammation)
• Lentigines (age or sun spots)

Hypopigmentation / Depigmentation

Causes:

Reduced melanin synthesis, melanocyte destruction, or genetic defects.

Examples:

• Vitiligo (autoimmune destruction of melanocytes, well-demarcated depigmented patches)
• Albinism (genetic defect in tyrosinase or melanin synthesis, generalized hypopigmentation)
• Pityriasis alba (mild post-inflammatory hypopigmentation, common in children)

Clinical Notes

• Pigmentation disorders may affect cosmesis and psychosocial health.
• Some disorders signal underlying systemic disease (e.g., Addison’s disease → generalized hyperpigmentation).
• Diagnosis is often clinical, sometimes aided by Wood’s lamp, biopsy, or genetic testing.