Skin Pigmentation (Decreased)

Distinguishing between hypopigmentation and depigmentation is crucial to narrowing the differential diagnosis. Hypopigmentation is a decrease in the level of pigmentation of the skin, whereas depigmentation is a total loss of skin pigment. Both can be either localized or generalized, which also helps narrow the differential. Skin biopsies are rarely helpful in this scenario.

Differential Diagnosis

• Vitiligo
  –Affects 1% of the population
  –Begins as a focal or diffuse (more common) hypopigmented patch that progresses to total loss of pigmentation of the affected skin (chalk white)
  –Usually symmetric; often tops of hands, perioral, periorbital skin, knees, elbows

• Pityriasis alba
  –Very common, especially in black children
  –Less distinct borders than in vitiligo, does not result in complete depigmentation
  –Plaques may appear lighter than surrounding skin and may be scaly
  –Often secondary to mild inflammation, such as tinea versicolor or atopic eczema
  –Completely reversible and does not cause permanent hypopigmentation

• Piebaldism
  –Congenital, permanent, and irreversible
  –Newborns often have a patch of white scalp hair and depigmented patches on the trunk with normally pigmented patches within these larger depigmented areas
• Chemical leukoderma (depigmentation)
  –May be caused by phenols, germicides, and many other caustic chemicals
  –Results in confetti-like macules of depigmentation in exposed skin
  • Albinism
    –Congenital
    –Disorder of melanin synthesis with several phenotypes, ranging from complete lack of pigmentation (white hair and translucent or “red” iris) to the more common diffuse hypopigmentation or “yellow” albinism that is prevalent in the black population
    –Affects the skin, hair, and eyes
    –Photophobia, decreased visual acuity, strabismus, and risk of skin cancer are the main problems faced by these patients
  • Congenital birthmarks (e.g., nevus anemicus, nevus depigmentosis) are isolated patches of hypo- or depigmentation that remain unchanged over time
  • Tuberous sclerosis is an inherited systemic disorder that results in hypopigmented macules in the shape of an “ash leaf ” on the trunk, and confetti-type depigmented macules on the arms/legs

  Workup and Diagnosis

  • History and physical examination
    –Determine whether the skin is completely depigmented (chalk white) or merely hypopigmented (lighter than surrounding skin but with residual pigmentation)
    –Vitiligo is easily diagnosed on clinical exam alone
    –Family or personal history of thyroid disease, other endocrine disorders, diabetes, or exposure to chemicals
    –History of allergies, hay fever, or asthma, which may support the diagnosis of postinflammatory hypopigmentation from atopic dermatitis
    –History of erythema or rash at the hypopigmented spot suggests pityriasis alba or postinflammatory hypopigmentation
    –Perform an eye exam to rule out strabismus or iris translucency that can be present in albinism
  • Wood's lamp examination can be used to highlight the borders of hypo- and depigmented patches
  • Skin biopsy can support the diagnosis of vitiligo but is not specific
  • Check thyroid function tests in patients with recent-onset vitiligo, and consider fasting glucose or ACTH stimulation test to rule out diabetes and Addison's
  • CBC (anemia, macrocytosis) may be indicated to screen for pernicious anemia, if suspected in patients with vitiligo

  Treatment

  • Topical steroids may stimulate repigmentation of vitiligo and pityriasis alba
  • Sunscreens are crucial to protect vulnerable skin
  • Since some patients develop vitiligo in areas of trauma (i.e., Koebner effect), trauma should be avoided
  • Repigmentation may be facilitated by systemic or topical photochemotherapy with psoralens plus UVA
  • Punch minigrafting from normal donor skin areas to vitiligo areas stimulates melanocyte repopulation
  • Patients with diffuse or unresponsive vitiligo may diffusely and irreversibly depigment their skin by applying monobenzylether or hydroquinone.
  • Treatment of any associated thyroid disorder or diabetes, pernicious anemia, etc., does not alter or improve the course of the associated vitiligo
  • Oral β-carotene can be taken long term by patients with diffuse vitiligo or albinism and may impart a more “normal” skin color

Book Source Details

• Book Title: In a Page: Signs and Symptoms
• Author(s): Scott Kahan, Ellen G. Smith
• Year of Publication: 2004
• Copyright Details: In a Page: Signs and Symptoms, Copyright © 2004 Lippincott Williams & Wilkins.

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Copyright Details: In a Page: Signs and Symptoms, Copyright © 2008 Williams & Wilkins.

More About Causes of Weak skin

• Back to symptom: Weak skin: Introduction (review 146 causes)
• Next Book Extract About Weak skin: BLEEDING UNDER THE SKIN (Differential Diagnosis in Primary Care)
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More About This Book: Title: In a Page: Signs and Symptoms Authors: Scott Kahan, Ellen G. Smith Publisher: Lippincott Williams & Wilkins Copyright: 2004 ISBN: 1-4051-0368-X

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• SKIN ULCERS (Differential Diagnosis in Primary Care)

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