Vitiligo

Pathophysiology

•    Autoimmune destruction of melanocytes

•    Associated with other autoimmune diseases:

o    Autoimmune thyroid disease (Hashimoto’s, Graves’)

o    Type 1 diabetes

o    Pernicious anaemia

o    Addison’s disease

Clinical features

•    Depigmented macules and patches, well-defined, often symmetrical

•    Common sites: periorificial areas (mouth, eyes), hands, extensor surfaces

Treatment

•    Potent topical steroids

•    Calcineurin inhibitors (tacrolimus) for facial lesions

•    Phototherapy (narrowband UVB)

•    Cosmetic camouflage

Post-inflammatory Hypo-/Hyperpigmentation

Causes

•    After eczema, psoriasis, burns, trauma

•    Common in darker skin types

Features

•    Hyperpigmentation: excess melanin deposition in basal layer

•    Hypopigmentation: temporary reduction in melanin or melanocyte function

Management

•    Often resolves over time

•    Sun protection to minimise contrast

Albinism

Pathophysiology

•    Congenital absence or defect in melanin synthesis, usually tyrosinase deficiency

•    Oculocutaneous types affect skin, hair, eyes

Clinical features

•    Generalised hypopigmentation of skin and hair

•    Ocular signs:

o    Nystagmus

o    Reduced visual acuity

o    Photophobia

Complications

•    Markedly increased risk of UV-induced skin cancers (BCC, SCC)

Melasma (Chloasma)

Pathophysiology

•    Hypermelanosis triggered by:

o    Hormonal changes (pregnancy, OCP use)

o    UV exposure

Clinical features

•    Symmetrical hyperpigmented macules, usually on cheeks, forehead, upper lip

Management

•    Sun protection

•    Topical depigmenting agents (hydroquinone, azelaic acid)

•    Consider retinoids

Addison’s Disease

Pathophysiology

•    Primary adrenal insufficiency → ↑ ACTH

•    ACTH cross-reacts with melanocyte-stimulating hormone (MSH)

Clinical features

•    Generalised hyperpigmentation, especially:

o    Sun-exposed areas

o    Pressure points (elbows, knees, knuckles)

o    Buccal mucosa and palmar creases (classic exam clue)

Extra Revision Pearls

•    Vitiligo + new hyperpigmentation → suspect Addison’s

•    Melasma: exacerbated by sunlight and oestrogen

•    Albinism: avoid excessive sun exposure; regular skin cancer surveillance

•    Post-inflammatory pigment changes: especially common in Fitzpatrick skin types IV–VI