Depigmented Macules: Diagnosis & Treatment

(i) Differential Diagnosis

The following conditions should be considered in the differential diagnosis:

• Vitiligo: The most likely diagnosis, characterized by well-defined, depigmented macules due to the loss of melanocytes.
• Pityriasis Alba: A mild form of eczema, often seen in children and young adults, presenting as slightly scaly, hypopigmented patches, typically on the face, arms, and upper trunk.
• Post-inflammatory Hypopigmentation: Occurs after inflammation (e.g., eczema, psoriasis, burns) and results in reduced melanin production in the affected area.
• Chemical Leukoderma: Caused by exposure to certain chemicals that destroy melanocytes.
• Tinea Versicolor: A fungal infection that can cause hypopigmented or hyperpigmented macules, often on the trunk. Usually presents with mild scaling.
• Idiopathic Guttate Hypomelanosis: Small, white spots that appear on sun-exposed areas, common in older individuals.
• Nevus Depigmentosus: Congenital hypopigmented macules, present at birth or shortly after.

(ii) Investigations

A systematic approach to investigation is essential:

• Detailed History: Family history of similar conditions, history of any preceding skin inflammation, chemical exposure, or systemic illnesses.
• Physical Examination: Thorough examination of the skin, hair, and mucous membranes to assess the extent and distribution of the lesions. Look for Koebner phenomenon (development of lesions at sites of trauma).
• Wood’s Lamp Examination: Vitiligo lesions appear bright white under Wood’s lamp, while other conditions may show different fluorescence patterns.
• Skin Biopsy: A punch biopsy from an affected area is crucial for definitive diagnosis. Histopathology in vitiligo shows a complete absence of melanocytes.
• Complete Blood Count (CBC): To rule out underlying systemic conditions.
• Thyroid Function Tests (TFTs): Vitiligo is often associated with autoimmune thyroid diseases.
• Antinuclear Antibody (ANA): To screen for other autoimmune disorders.
• Venereal Disease Research Laboratory (VDRL) test: To rule out syphilis, which can rarely cause hypopigmentation.

(iii) Treatment of Vitiligo (Most Common Condition)

Treatment for vitiligo aims to halt disease progression, repigment the affected areas, and improve the patient’s quality of life. The approach is often multimodal.

• Topical Corticosteroids: Potent topical corticosteroids can be used for limited areas of vitiligo, especially in the early stages, to stimulate melanocyte activity. Prolonged use can cause side effects like skin atrophy.
• Topical Calcineurin Inhibitors (Tacrolimus, Pimecrolimus): Useful for facial and intertriginous areas, with fewer side effects than corticosteroids.
• Phototherapy:
  • Narrowband UVB (NB-UVB): The most commonly used phototherapy modality, effective in inducing repigmentation. Requires regular sessions over several months.
  • PUVA (Psoralen + UVA): Less commonly used due to increased side effects.
• Excimer Laser: Effective for localized vitiligo, delivering a high-intensity beam of UVB light.
• Surgical Options: For stable vitiligo, surgical techniques like melanocyte-keratinocyte transplantation can be considered.
• Depigmentation Therapy: For extensive vitiligo, depigmentation of the remaining normal skin can be considered as a last resort.
• Psychological Support: Vitiligo can have a significant psychological impact. Counseling and support groups can be beneficial.

Important Considerations: Sun protection is crucial to prevent sunburn and further damage to the depigmented skin. Treatment response varies significantly among individuals.