Disorders of Pigmentation

Vitiligo

Vitiligo is an acquired multifactorial disorder resulting in the autoimmune destruction of pigment-producing cells in the skin. Patients present with well-circumscribed depigmented macules and patches on the skin and mucous membranes, in either a localized or generalized distribution.

  • History: Patients report the new onset of depigmented patches that may appear milk white.
  • Symptoms: Lesions are asymptomatic (no itching, pain, or burning).
  • Course: Unpredictable; can be progressive with extension over a few months then stabilization.
  • Family History: 20-30% of affected individuals report vitiligo in a first or second-degree relative.
  • Associated Conditions: Ask about symptoms of other autoimmune disorders (e.g., autoimmune thyroid disease, rheumatoid arthritis).

Distribution Patterns:

  • Generalized:
    • Vitiligo vulgaris: Scattered depigmented patches in a widespread distribution.
    • Acrofacial vitiligo: Affects the distal extremities and the face.
    • Universal vitiligo: Complete or nearly complete depigmentation of the skin.
  • Localized:
    • Focal type: One or two depigmented macules without a segmental distribution.
    • Segmental type: Lesions are typically unilateral and do not cross the midline.
Clinical Appearance

Completely depigmented skin with no underlying inflammation, atrophy, or scale. Acral distribution is common. Involvement of hair follicles (eyebrows, eyelashes) is called poliosis. Repigmentation occurs in a follicular distribution.

Diagnosis and Management

Vitiligo is usually a clinical diagnosis based on the characteristic appearance of depigmented patches or macules without inflammation.

  • Tests: No specific tests are required, but blood tests (e.g., TSH, ANA) can be performed to exclude other autoimmune disorders if clinically indicated.
  • Late Onset Vitiligo: Perform a total body skin examination to look for suspicious moles, as late-onset vitiligo can occur secondary to melanoma.
Differential Diagnosis:
  • Post-inflammatory depigmentation: History of a preceding inflammatory cause (e.g., eczema).
  • Chemical leukoderma: Pigment loss following exposure to chemicals that destroy melanocytes; history of chemical exposure.
  • Lichen sclerosus: Inflammatory disorder, commonly in the genital area; lesions are associated with atrophy, erythema, and pruritus.

Oculocutaneous Albinism

Oculocutaneous albinism is a group of genetic disorders characterized by hypopigmentation due to the partial or total absence of melanin in the skin, hair follicles, and eyes.

  • History: Widespread hypopigmented skin from birth (inherited condition).
  • Symptoms: Pale skin, hair, and eyes; easily sunburnt; increased risk of skin cancers; ocular problems due to decreased melanin in the eyes.
  • Genetics: Autosomal recessive disorder; parents are usually unaffected carriers.

Examination Findings

Light hair, skin, and eyes. Assess for ocular abnormalities (strabismus, nystagmus, decreased visual acuity) and refer to ophthalmologist if needed. Perform a full body skin examination to look for suspicious lesions.

Dignosis and Management

Albinism is usually a clinical diagnosis based on its characteristic appearance.

  • Regular Examinations: Patients should undergo regular total body skin examinations.
  • Biopsy: Any suspicious lesions or moles should be biopsied.
Differential Diagnosis
  • Full body vitiligo: Vitiligo presents with well-circumscribed depigmented macules, whereas albinism presents with widespread hypopigmentation.
    • Vitiligo: Melanocyte destruction, reduced number of melanocytes.
    • Albinism: Defect in melanin biosynthesis pathway, decreased melanin production, normal number of melanocytes.
    • Vitiligo: Acquired later in life.
    • Albinism: Usually present at birth.

Melasma

Melasma is a common chronic acquired disorder of hyperpigmentation, resulting in brown to gray macules and patches on sun-exposed areas of skin. It most commonly affects females with darker skin types.

  • History: Progressive development of hyperpigmented dark brown or brown-gray macules and patches with irregular borders on the face and less commonly on the arms.
  • Symptoms: Lesions are usually symmetrically distributed and asymptomatic.
  • Triggers: Exposure to sunlight, pregnancy, certain medications (oral contraceptives, hormonal therapy, photosensitizing drugs like antiepileptics).

Clinical Subtypes:

  • Centrofacial: Hyperpigmented patches involve the forehead, cheeks, nose, upper lip, with sparing of the fulcrum and nasolabial folds.
  • Malar: Patches involve the cheeks and nose.
  • Mandibular: Lesions are present along the jawline.

Clinical Appearance

Hyperpigmented patches in a symmetrical distribution, often with irregular borders, classically found on the face.

Diagnosis and Management

Melasma is diagnosed clinically; no specific tests are required.

Differential Diagnosis
  • Post-inflammatory hyperpigmentation: History of preceding inflammation.
  • Solar lentigo: Typically found in lighter skin types; lesions are not found in a symmetrical distribution like melasma.
  • Exogenous ochronosis: History of application of topical hydroquinone to the skin followed by progressive skin darkening.

Pityriasis Versicolor

Pityriasis versicolor is a common benign superficial fungal infection of the skin caused by Malassezia, resulting in dyspigmentation.

  • History: Multiple oval round macules, patches, and plaques, which can be brown (hyperpigmented), white (hypopigmented), or red; may present as fine red scaly plaques.
  • Symptoms: Typically asymptomatic, but can be mildly pruritic.
  • Climate: More common in hot or humid climates; may clear in winter and recur in summer.
  • Risk Factors: High-temperature or humid climate, oily skin, excessive sweating, immunodeficiency, poor nutrition, pregnancy, or use of corticosteroids.

Examination Findings

Very fine overlying scale may be elicited by scratching or stretching the skin surface. Lesions usually affect the trunk, neck, and upper arms.

Diagnosis

Pityriasis versicolor is usually a clinical diagnosis; no specific tests are required.

  • Microscopy (if available): Scraping of the skin reveals the typical "spaghetti and meatball" pattern.
Differential Diagnosis
  • Secondary syphilis: If fine red scaly plaques are present, consider RPR to rule out syphilis.
  • Post-inflammatory dyspigmentation: History of preceding inflammation.
  • Guttate psoriasis: Look for other features of psoriasis such as involvement of the nails, the scalp, or joint pain.
  • Pityriasis alba: Hypopigmented macules, patches, or thin plaques typically on the face; occurs on the background of someone with atopic features.
  • Tinea corporis: Typically, presents with annular plaques; not as widespread as pityriasis versicolor; skin scraping would reveal hyphae.

Post-inflammatory Pigment Changes

Post-inflammatory pigment changes are acquired disorders of hyperpigmentation, hypopigmentation, or depigmentation occurring secondary to a variety of insults to the skin.

  • Causes: Cutaneous inflammation, physical or chemical injuries.
  • Presentation: Patches or macules that can have associated areas of atrophy.
  • History: Preceding inflammation, physical injury, or chemical injury.

Etiology

  • Inflammatory causes: Acne vulgaris, atopic dermatitis, impetigo, insect bites, etc.
  • Iatrogenic causes: Medical procedures such as biopsies, cryotherapy, intralesional corticosteroids, laser therapy, and surgical procedures.
  • Injury causes: Thermal or chemical burns, or lacerations.

Clinical Findings

Hyperpigmented, hypopigmented, or depigmented patches and macules located at the site of the original disease after it has healed.

  • Color: Lesions range from white to light brown to black.
  • UV Exposure: May become darker if exposed to UV light.
  • Associated Findings: May be associated with atrophic or hypertrophic scars (e.g., ice pick scars in acne vulgaris, atrophy in discoid lupus).

Diagnosis and Management

Diagnosis is usually clinical, based on history and patient reporting preceding inflammation in the affected areas.

Differential Diagnosis

Vitiligo, pityriasis versicolor, pityriasis alba, solar lentigo, etc. The clue is the history of preceding inflammation.

Leprosy

Leprosy is a slowly progressive infectious disease caused by Mycobacterium leprae, characterized by granuloma formation in the nerves and skin. Clinical manifestations primarily involve the skin and the nervous system.

  • Skin Lesions: Hypopigmented or erythematous and often lack sensation; hypomelanotic macules may be the earliest expression.
  • Neurological Symptoms: Numbness is the first presenting symptom in more than 90% of cases; temperature sensation is lost first, followed by light touch, pain, and deep pressure.
  • History: Possible history of close contact with a patient known to have leprosy.
  • Incubation Period: Extremely long, ranging from 6 months to 20 years.

Subtypes of Leprosy

  • Tuberculoid Leprosy (Paucibacillary):
    • Well-defined red or hypopigmented plaques with raised borders.
    • Loss of sweating and sensation in the lesions.
    • Thickened or tender nerves on palpation.
  • Lepromatous Leprosy (Multibacillary):
    • Multiple poorly defined erythematous macules, papules, nodules, and plaques.
    • Widespread and symmetrical distribution.
    • Common sites of involvement are the face, buttocks, and lower extremities.
    • Infiltration of the skin of the forehead can lead to Leonine facies (thickening and infiltration of the skin on the forehead).
  • Borderline Leprosy:
    • Mixed features of both tuberculoid and lepromatous leprosy.
    • Lesions can be less well-defined and have an asymmetrical distribution.
    • The severity depends on whether the patient is leaning towards the lepromatous or the tuberculous pole of the spectrum.

Examination Findings

  • Sensation Testing: Test sensation within the cutaneous lesions (pain, temperature, and sensation).
  • Nerve Examination: Palpate the superficial peripheral nerves.
  • Complications: Assess for neuropathic changes such as muscle atrophy, flexion contractures of the digits, and secretory disturbances such as dry eyes and a dry nasal mucosa.

Diagnosis

Confirm the diagnosis with a punch biopsy of the skin.

  • Histology: Presence of granulomatous inflammation.
  • Special Stains: Fite stain can help identify the Mycobacterium leprae organisms.
Differential Diagnosis

Depends on the clinical variant of leprosy.

  • Hypopigmented lesions: Post-inflammatory hypopigmentation.
  • Annular lesions: Tinea corporis or psoriasis.
  • Nodular lesions: Lymphoma or sarcoidosis.
  • Neurological findings: Consider additional causes for peripheral neuropathy such as diabetes.