Chapter 60

Pigmentation Changes (Vitiligo)

Maria Isabel Romano

Definition and Epidemiology

Vitiligo is a skin disorder characterized by either a lifelong or a rapid disappearance of pigment-producing melanocytes in the epidermis and hair follicle. Lack of melanin leads to the appearance of progressive, symmetrically patterned, milky-white macules that merge to form larger depigmented areas. The macules give a variegated appearance to the skin that is similar to the white patches on a Holstein calf, hence the origin of the word from the Greek vitellius, which means “calf.” The disease is psychologically troublesome, affecting the patient’s self-esteem and interpersonal relationships. Although the disease shows no increased prevalence among dark-skinned racial groups, the variegated appearance of the skin proves to be especially traumatic for dark-pigmented patients. The appearance of vitiligo resembles leprosy, but the lesions of vitiligo do not have the anesthetic property of leprosy. However, the similarity in appearance to leprosy presents a social stigma for those patients with vitiligo living in leprosy-affected areas of the world.¹ The disease manifests in two forms: type A, a nondermatomal distribution; and type B, a segmental or dermatomal distribution (zosteriform) characterized by rapid spread.²

Vitiligo is seen in 1% to 2% of the general population without regard to race, ethnic origin, or gender.²^,³ Although some patients have no vitiligo in their family history, the condition has an inherited tendency; in 30% of cases, a family history of vitiligo in parents, offspring, or siblings is reported.² Familial cases of vitiligo have been associated with autoimmune endocrine disorders; studies indicate that there is a genetic locus in affected individuals, and a possible pathogenic connection between vitiligo and oxidative damage exists.⁴ A family history of thyroid disease, pernicious anemia, systemic lupus erythematosus, inflammatory bowel disease, and vitiligo is associated with a risk for development of the condition.⁶ Disease onset occurs between 10 and 30 years of age; 50% of the cases occur before the age of 20 years, and fewer cases are reported in infancy and old age.²^,⁵^,⁶^,⁷

Pathophysiology

The exact cause of vitiligo is not known. Multiple pathogenic theories exist and are under investigation, including autoimmune involvement, viral causes, decreased melanocyte survival, genetic defects in the structure of melanocytes, and neurochemical destruction of melanocytes.⁸^,⁹ Except for the absence of melanocytes, skin function is normal. There is a progressive destruction of pigment-producing cells at the border of the dermis and epidermis. The nonsegmental (nondermatomal) variety of vitiligo is associated with a small risk of autoimmune-related disorders, such as type 1 diabetes mellitus and thyroid disease.²

Several theories exist to explain the phenomenon of vitiligo. The autoimmune theory proposes that there is a destruction of the cutaneous melanocytes with loss of the melanin-producing pigment. Histologic examination indicates that lymphocytes build up within the dermis and are involved in the destruction of the melanocytes. Coexisting diseases such as alopecia areata, autoimmune thyroid disorders, Addison disease, atrophic gastritis, pernicious anemia, and type 1 diabetes underscore the relationship of dermatomal vitiligo to autoimmunity. Serum autoimmune antibodies against melanocytes, thyroid and adrenal tissue, islet cells, gastric parietal cells, and intrinsic factors have been demonstrated.

A second explanation, the neurogenic theory, supposes that a toxic substance is released by the peripheral nerve endings and interferes with the production of melanin. A third theory suggests a defect in the natural protective mechanism of melanin synthesis by melanocytes. Toxic substances accumulate during normal melanin production and later precipitate the destruction of the melanocytes.⁷^–⁹ The variation in presentation and progression of the two types of vitiligo indicates that the underlying pathologic condition for the two forms of disease may be distinctly different.

Clinical Presentation

Vitiligo is characterized by a progressive and invasive hypopigmentation of the skin that is found on sun-exposed areas and extensor surfaces of the upper body. Most patients have no other clinical findings.² Vitiligo manifesting with well-defined areas of white hair is referred to as poliosis.⁸ In general, the onset of vitiligo may follow stress; an injury to the skin, such as a burn, bruise, or contusion (Koebner phenomenon); and sunburn.⁸ Vitiligo should not be confused with postinflammatory hypopigmentation, in which the skin has a faded pigment appearance rather than an absence of pigment.¹⁰ Chemicals, including phenols and catechols, may cause depigmentation of the skin; therefore any history of a patient with vitiligo should include questions about chemical exposure.⁶ In fair-skinned individuals, the disease may go undetected until summer, when the sun-exposed areas tan and the melanin-free areas appear a contrasting chalky white.

Physical Examination

The extensor surfaces may have been traumatized previously; depigmentation first appears here in a symmetric fashion typical of the more common nondermatomal variety. The segmental variety is more often seen in children and follows a dermatomal distribution that progresses more rapidly. The dermatomal variety is not likely to be associated with autoimmune disorders or Koebner phenomenon.² The border is not sharply demarcated but instead exhibits a tricolored, uneven appearance.⁸ Box 60-1 indicates the usual locations of the hypopigmented lesions of vitiligo. Because melanocytes are located in the eyes, ocular changes, such as uveitis and pigmentary changes in the fundus, can occur; other findings may include healed chorioretinitis and iritis.²^,⁸

Box 60-1

Common Locations for Hypopigmented Vitiligo Lesions