What’s causing this facial rash involving darker patches of skin?

Clinical features

• Gradual onset, symmetrical hyperpigmented macules and patches, most commonly on sun exposed areas of the face.
• Colour ranges from light brown to dark brown or grey-brown, depending on depth of pigment and skin phototype.
• Borders may be well defined or slightly irregular; lesions are flat and non-scaling.
• Classically affects the centrofacial pattern (forehead, cheeks, upper lip, chin), but may also present in a malar (cheeks and nose) or mandibular distribution.
• Usually asymptomatic. No pruritus, pain or inflammation.
• Primary concern is cosmetic; patients may report worsening with sun exposure or during/after pregnancy.
• Psychosocial impact: facial hyperpigmentation can cause significant distress, reduced self-confidence, social anxiety and impact on quality of life.

Epidemiology

• More common in women than men (approximately 9:1 female predominance).
• Frequently affects women of reproductive age; often associated with pregnancy (‘mask of pregnancy’) or use of combined oral contraceptives or HRT.
• Higher prevalence in individuals with darker skin phototypes.
• More common in populations with higher cumulative UV exposure.

Diagnosis

• Clinical evaluation:
  • History: gradual onset, symmetry, relationship to pregnancy, hormonal contraception, HRT, sun exposure, use of fragranced cosmetics or photosensitising products. Ask about duration, progression and prior treatments.
  • Medication review: combined oral contraceptives, HRT, certain antiseizure medication.
• Examination: assess distribution (centrofacial, malar, mandibular), colour and symmetry. Confirm absence of scale, erythema or scarring.
• Consider skin phototype and degree of sun damage.
• Assess psychosocial impact and patient expectations regarding treatment (realistic outcomes, chronicity).
• Investigations:
  • Usually none required; diagnosis is clinical.
  • Consider endocrine assessment only if clinical features suggest an alternative diagnosis (e.g., Addison’s disease with systemic symptoms).

Differential diagnosis

• Post inflammatory hyperpigmentation – history of preceding inflammation (acne, eczema, trauma) with less symmetrical distribution.
• Solar lentigines – discrete, well demarcated macules rather than confluent patches.
• Drug induced hyperpigmentation – consider medication history.
• Addison’s disease – diffuse hyperpigmentation including mucosa, palmar creases, associated systemic features (weight loss, hypotension).
• Pigmented contact dermatitis (Riehl’s melanosis) – often with history of cosmetic or fragrance exposure.

Red flags

• Mucosal pigmentation, systemic symptoms (fatigue, weight loss, hypotension) – consider endocrine causes (e.g., Addison’s disease) and investigate appropriately.
• Rapidly changing, irregular or variegated pigmented lesions – consider melanoma and refer via urgent suspected cancer pathway if suspicious.
• Significant psychological distress impacting mental health – consider holistic management and support.
• Diagnostic uncertainty or atypical distribution – consider dermatology referral.

Management

• Education and photoprotection: Strict, broad spectrum (UVA and UVB) sunscreen daily (SPF 30–50), even in winter; advise reapplication and use of hats/physical barriers.
• Visible light protection (iron oxide–containing tinted sunscreens) may be beneficial. Advise avoidance of known triggers where possible (e.g., consider alternative contraception if temporally related and appropriate).
• Topical therapy:
  • Hydroquinone 2–4 % (short term use; unlicensed, usually specialist initiated in UK practice).
  • Combination creams (e.g., hydroquinone + retinoid + mild topical corticosteroid) are effective but usually initiated in dermatology or in private practice.
  • Azelaic acid 15–20 % may be considered in primary care; also useful if concurrent acne.
  • Topical retinoids (e.g., tretinoin) may be used under specialist guidance.
  • Emphasise that improvement is gradual (often 3–6 months) and relapse is common without ongoing photoprotection.
• When to refer:
  • Diagnostic uncertainty.
  • Failure of adequate trial (at least 3–6 months) of strict photoprotection and topical therapy.
  • Severe or refractory melasma significantly affecting quality of life.
  • Consideration of procedural treatments (chemical peels, laser, intense pulsed light) – these carry risk of post inflammatory hyperpigmentation, particularly in darker skin types, and should be undertaken by experienced practitioners.

Patient education

• Understanding the condition:
  • Melasma is a common, benign disorder of hyperpigmentation driven by UV exposure, hormonal factors and genetic predisposition. It is not infectious or malignant.
  • The condition is chronic and relapsing; while treatments can lighten pigmentation, recurrence is common, particularly with sun exposure.
• Treatment expectations:
  • Improvement is gradual; strict adherence to photoprotection is essential for any treatment to be effective.
  • Overuse of potent topical corticosteroids (particularly on the face) should be avoided due to risk of skin atrophy and steroid-induced rosacea.
• Hormonal influences: pregnancy related melasma may partially improve postpartum but can persist.
• Psychological impact: acknowledge cosmetic concerns and validate distress; discuss camouflage options (medical grade cover creams), and signpost to reputable dermatology resources if needed.
• Encourage review if pigmentation changes in character, becomes asymmetrical, or new systemic symptoms develop.