Disorders of Pigmentation and Dermatologic Considerations in Ethnic Skin



Disorders of Pigmentation and Dermatologic Considerations in Ethnic Skin


Heather Onoday






THE MELANOCYTE


I. OVERVIEW

The melanocyte comprises approximately 5%-10% of the cellular component of the interfollicular epidermis and an equal component of the hair bulb. They are cells of neural crest origin. (Refer to the discussion of melanocyte in the Cells in the Epidermis section in Chapter 1.) Melanocytes reside in the basal layer of epidermis, where they form the epidermal melanin units as a result of the relationship between one melanocyte and 30-40 associated keratinocytes. The ratio of melanocytes to keratinocytes is 1:10 in the epidermal basal layer.

A. Characteristics of the melanocyte

1. Limited in number.

2. Major synthetic product is melanin.

a. Melanin is the primary determinant of skin color and hair color.

b. Melanin accounts for racial and ethnic skin pigmentation differences.

c. Melanin functions to:

(1) Absorb ultraviolet light

(2) Protect genome of dividing basal keratinocytes and melanocytes

(3) Scavenge free oxygen radicals

3. Melanocytes can up- or downregulate pigmentation in response to:

a. Physiologic stimuli (e.g., production of melanocyte stimulating hormone, MSH)

b. Environmental stimuli (e.g., ultraviolet radiation).

c. Pathologic stimuli (e.g., trauma)

B. Hypothesized to contribute to epidermal homeostasis during inflammation


II. DISORDERS OF PIGMENTATION

A. Disorders of pigmentation may present as either hypo- or hyperpigmentation (too much or too little melanin).

1. Can be localized or diffuse

2. Can be acquired or congenital


B. Acquired hypopigmentation

1. Vitiligo

2. Postinflammatory (e.g., after laser treatment)

3. Inflammatory disorders (e.g., psoriasis, atopic dermatitis)

4. Neoplasms (e.g., cutaneous T-cell lymphoma)

5. Postinfection

a. Bacteria: Treponema pertenue, Treponema carateum, and Mycobacterium leprae

b. Yeast: Pityrosporum orbiculare

c. Protozoan: Leishmania donovani

d. Helminth: Onchocerca volvulus

e. Fungus: tinea versicolor

C. Congenital hypopigmentation

1. Albinism

2. Piebaldism

3. Tuberous sclerosis

4. Hypomelanosis of Ito (pigmentary mosaicism)

D. Acquired hyperpigmentation

1. Melasma

2. Chemically induced

3. Melanocytic nevi

4. Ephelides (freckles): small orange-brown or lightbrown macules promoted by sun exposure, fading in winter months; usually on face, arms, and back; benign

5. Fixed drug eruptions or phototoxic eruptions

6. Café au lait spots: uniformly pale-brown macules seen on any cutaneous surface; present at birth; six or more macules of greater than 1.5 cm would warrant a workup for neurofibromatosis (von Recklinghausen disease)

7. Postinflammatory (e.g., thermal burns)

E. Diffuse brown hyperpigmentation: Addison disease


DISORDERS OF HYPOPIGMENTATION


VITILIGO


I. OVERVIEW

A distinctive disorder of pigmentation in which the affected epidermis is devoid of one of its three main cell types (melanocytes) leading to a lack of melanin-based pigmentation in those affected areas.

A. Definition: acquired loss of pigmentation characterized histologically by complete absence of melanocytes in association with a total loss of epidermal pigmentation

B. Etiology

1. Exact pathogenesis is unclear.

2. Generalized symmetric form. Thought to be an autoimmune disease associated with antibodies (vitiligo antibodies) and cell-mediated cytotoxicity directed against melanocytes.

3. May be genetic (a predisposing factor); over 30% of affected individuals have reported vitiligo in a parent, sibling, or child; polygenic (i.e., not caused by a single gene defect)

4. Other theories include cytotoxic mechanisms, an intrinsic defect of melanocytes, oxidant-antioxidant mechanisms, and neural mechanisms.

5. No definitive precipitating factor has been established; anecdotal correlation with the following environmental factors:

a. Psychological stress

b. Physical trauma

c. Pregnancy

d. Oral contraceptives

e. Sunlight and artificial ultraviolet light

f. Illness

Note: These associations are frequently observed in a high percentage of normal individuals and have not been epidemiologically shown to occur more frequently in patients with vitiligo.

C. Pathophysiology

1. Caused by a loss of melanin from the epidermis.

2. A decrease in the number of melanocytes in affected areas.

3. Pigment loss may be localized, generalized, or universal.

D. Incidence

1. Worldwide prevalence of vitiligo is between 0.5% and 2%.

2. Up to 2.16% of children and adolescents are affected with vitiligo.


II. ASSESSMENT

A. History

1. Ask about initial presentation. 2. Ask about any somatic complaints or vision problems that may be associated with vitiligo.

a. Migraines

b. Decrease in hearing or pain with hearing (melanin may play important role in the structure and function of the auditory system)

3. Assess other diseases associated with vitiligo

a. Thyroid disease (hypo- and hyperthyroidism, Grave disease)

b. Diabetes mellitus

c. Pernicious anemia

d. Addison disease

e. Multiglandular insufficiency syndrome

f. Alopecia areata

g. Melanoma

h. Lupus erythematosus

i. Rheumatoid arthritis

4. Diseases that have been reported in patients with vitiligo

a. Immune deficiency diseases

b. Multiple myeloma

c. Dysgammaglobulinemia

d. Cutaneous T-cell lymphoma

e. Thymoma

B. Clinical manifestations

1. Initial presentation and progression: variable; but genital, anal, axillary, and periorbital are often first areas affected.

2. Usually a depigmented macule or patch (1 to 3 cm)

3. Distinct margins

4. Variations in color and margins can occur (margin may be hyperpigmented, hypopigmented, or exhibit erythema, which is suggestive of an inflammatory process).

5. Face, joints, hands, and legs are the most commonly affected areas (Figure 17-1).







FIGURE 17-1. Vitiligo. (Copyright 2015 by the American Academy of Dermatology. All rights reserved.

6. Mucous membranes may be affected.

7. Often symmetrical in presentation (Figure 17-2).

8. Classification of patterns of distribution

a. Localized

(1) Focal: one or more macules in one area

(2) Segmental: dermatomal pattern

(3) Mucosal: localized on mucous membranes

(4) “Lip-tip” pattern: involves skin around the mouth as well as on the distal fingers and toes; lips, nipples, and genitalia (tip of penis)

b. Generalized often remarkably symmetrical

(1) Acrofacial: distal extremities and face

(2) Vulgaris: diffuse presentation

(3) Mixed: combination of acrofacial and vulgaris






FIGURE 17-2. Vitiligo symmetry. (Copyright 2015 by the American Academy of Dermatology. All rights reserved.)

c. Universal-depigmented areas cover almost the entire body

9. Associated cutaneous findings

a. White and prematurely gray hair

b. Alopecia areata

c. Halo nevi

C. Differential diagnosis

1. Piebaldism

2. Lupus erythematosus

3. Tinea versicolor (pityriasis versicolor)

4. Pityriasis alba

5. Lichen sclerosus et atrophicus

6. Cutaneous T-cell lymphoma

7. Sarcoidosis

8. Scleroderma

9. Postinflammatory pigmentary alteration (PIPA)

10. Tuberous sclerosis

11. Hypomelanosis of Ito

12. Incontinentia pigmenti


III. COMMON THERAPEUTIC MODALITIES

A. Goals of treatment

1. Restore normal function to epidermis

2. Cosmesis

B. Medical therapy: aimed at stimulating proliferation and migration of melanocytes

1. Topical steroids

a. Topical class 3 can be employed.

b. Applied daily for several months or longer.

c. If pigmentation not seen within 3 months, steroid should be stopped for approximately 6 months and then may be reinstituted or another treatment modality used.

2. Topical immunomodulators

a. Seem to be equally effective as topical steroids, especially when used in the face and neck region

b. Off-label indication for vitiligo

c. Black box warning for possible risk of cancer

3. Phototherapy (see Chapter 6, Phototherapy, for comprehensive discussion)

a. Psoralen plus Ultra Violet A light (PUVA) either topical or systemic.

b. Topical or systemic PUVA is used two to three times weekly for several months; if no response, stop treatment for at least 6 months before trying again.

c. UVB narrowband (310- to 315-nm wavelength), two to three times weekly.

d. UVB narrowband therapy with excimer laser produces monochromatic rays at 308 nm to treat limited, stable patches of vitiligo, treated two to three times weekly, averaging 24 to 48 sessions.

4. Depigmentation

a. Used when there is involvement of more than 50% of the skin surface.

b. Monobenzone (monobenzyl ether of hydroquinone [MBEH]) is applied to skin twice daily until satisfactory depigmentation is achieved.


(1) Frequently requires strength of 20% to 40% to induce necrotic death of melanocytes

c. Informed consent from the patient as depigmentation is permanent and increases photosensitivity and pruritus.

C. Surgical therapy

1. Punch grafts: technique similar to hair transplantation

a. Donor sites are pigmented areas of the skin.

b. Transplanted into depigmented areas of the skin.

c. Held in place with pressure dressings.

d. Repigmentation seen in 4 to 6 weeks after transplantation.

e. Residual pebbled skin may result, which can be cosmetically unacceptable.

2. Minigrafts: variant of the punch graft using smaller donor grafts to minimize pebbling

3. Suction blisters

a. Epidermal grafts are obtained by vacuum suction.

b. Blister roof is removed intact and grafted to depigmented site.

c. Good for large areas of depigmentation.

d. May be combined with phototherapy.

e. Repigmentation using this method may cause a mottled appearance.

4. Autologous cultures

a. Use autologous cultured melanocytes and keratinocytes from unaffected donor skin.

b. Applied to recipient sites that have had epidermis removed by suction, cryotherapy, or dermabrasion.

c. Color may be mottled or incompletely re-pigmented.

5. Autologous melanocyte grafts

a. Variant of autologous cultures.

b. Injected into the depigmented site or used on superficially dermabraded skin.

c. Culturing melanocytes requires expertise and several months.

d. Spread of pigmentation is minimal.

6. Problems with surgical therapies

a. Graft failure.

b. Donor sites may become depigmented (isomorphic response).

c. Risk of infection. d. Risk of scarring in donor sites. e. May be cost prohibitive.

Note: Five general options for management are sunscreens, cover-up, repigmentation, minigrafting, and depigmentation.


ALBINISM


I. OVERVIEW

A group of inherited disorders that are characterized by little or no production of melanin

A. Definition: genetically defined defect in the melanocyte system of the eye, skin, or both

B. Etiology

1. One of four genetic mutations

C. Pathophysiology

1. Mutations in the gene disrupt the ability of cells to synthesize melanin.

2. Two classifications

a. Oculocutaneous albinism (OCA)

b. Ocular albinism (OA)

D. Incidence

1. OCA: 1:17,000

2. OA: not established


II. ASSESSMENT

A. History

B. Clinical manifestations

1. OCA: diluted skin/hair pigmentation

a. Skin

(1) In light-skinned individuals, skin is very light.

(2) In darkly pigmented individuals, large, pigmented freckles in light-exposed areas may be seen.

b. Hair

(1) In darkly pigmented individuals, hair is yellow to yellowish-brown.

(2) In lighter-skinned individuals, hair may range from white to cream, yellow to yellow-red, to vibrant red.

c. Eye

(1) Iris: blue/gray and translucent.

(2) Retina and choroid: paucity of pigment.

(3) In darkly pigmented individuals, the iris will be pale blue to cinnamon brown.

(4) Photophobia and nystagmus seen in all races.

(5) Visual acuity is decreased.

2. OA

a. Decrease or absence of melanin in the iris and retinal pigment epithelium.

b. Nystagmus present.

c. Iris translucency may occur.

d. Decrease in visual acuity.

e. Hair and skin color are normal.


III. COMMON THERAPEUTIC MODALITIES

A. Treatment goals are surveillance and preventing complications.

B. Sunscreen use.

C. Regular skin inspection for early detection of skin cancers.

D. Appropriate eye protection.


PIEBALDISM


I. OVERVIEW

Congenital absence of melanocytes in affected areas of the skin and hair (depigmentation) that may have spontaneous expansion and contraction

A. Definition: disorder of hypopigmentation, which involves skin and hair only

B. Etiology

1. Autosomal dominant mutation of the c-kit or SNA12 gene, rare


C. Pathophysiology

1. Hypomelanosis

2. Histologically, absence or markedly decreased melanocytes in affected areas

D. Incidence: 1:20,000 births


II. ASSESSMENT

A. History

1. Screen for deafness.

2. Screen for congenital megacolon particularly in infants.

B. Clinical manifestations

1. Characteristic pattern

a. White forelock

b. Occasionally white macules/patches on forehead, chin c. Lack of pigmentation

(1) Trunk

(2) Anterior thorax

(3) Abdomen

(4) Midarm to wrist

(5) Midthigh to midcalf (anterior and posterior)

(6) Normal pigmentation of hands, upper part of arm, shoulders, upper thighs, and feet to midcalf

2. Two features to distinguish piebaldism from vitiligo

a. Presence of islands of normal pigmentation (Figure 17-3) in areas of hypomelanosis

b. Characteristic distribution

c. Congenital

d. Frequently hereditary autosomal dominant pattern can be observed in family members.






FIGURE 17-3. Piebaldism. (Copyright 2015 by the American Academy of Dermatology. All rights reserved.)


III. COMMON THERAPEUTIC MODALITIES

A. Minigrafts: most successful

B. Culture grafts: not always cosmetically acceptable

C. PUVA: not always cosmetically acceptable


TUBEROUS SCLEROSIS


I. OVERVIEW

Also called tuberous sclerosis complex. Hypopigmentation is one of the earliest clinical signs of tuberous sclerosis.

A. Definition: rare, multisystem, genetic disease that causes benign tumors to grow in the brain and on other vital organs such as the kidneys, heart, eyes, lungs, and skin. Also affects the central nervous system, resulting in symptoms including seizure, developmental delay, and behavioral abnormalities.

B. Etiology

1. Genetic

C. Pathophysiology

1. Melanocytes present

2. Melanosomes in melanocytes decreased and poorly melanized

D. Incidence

1. 1:6,000 births


II. ASSESSMENT

A. History

B. Clinical manifestations

1. Common locations

a. Trunk

b. Lower extremities

2. Configurations

a. Ash leaf spot: lance-ovate (round at one end and pointed at the other); considered as a tertiary feature of tuberous sclerosis (Figure 17-4)

b. Oval

c. Polygonal

d. Shagreen patch area of thickened, elevated pebbly skin, usually found on lower back (Figure 17-5)






FIGURE 17-4. Ash leaf macule, seen in tuberous sclerosis. (Copyright 2015 by the American Academy of Dermatology. All rights reserved.)







FIGURE 17-5. Shagreen patch, seen in tuberous sclerosis. (Copyright 2015 by the American Academy of Dermatology. All rights reserved.)

3. May see multiple 1- to 3-mm macules (“confetti-like”) with poliosis (loss of melanin) of scalp, hair, eyebrows, and eyelashes

4. Hypopigmented spots of the iris and fundus

5. Wood lamp enhances lesions in light-skinned patients.


III. COMMON THERAPEUTIC MODALITIES

None for skin lesions


DISORDERS OF HYPERPIGMENTATION


MELASMA


I. OVERVIEW

Disorders of hyperpigmentation can be caused by any of the following factors: hereditary/developmental, metabolic, endocrine, inflammatory, chemically induced, nutritional, or neoplastic. Melasma is one of the most commonly seen disorders of hyperpigmentation.

A. Definition: acquired, brown hypermelanosis of the face. Also called chloasma faciei

B. Etiology

1. Secondary to an increase in the number and activity of melanocytes

2. No known cause. Melasma has been linked to:

a. Oral contraceptives

b. Pregnancy

c. Cosmeceutical or medication (usually a phototoxic or allergic reaction)

d. Genetic predisposition

e. Endocrine (progesterone and estrogen both have an effect on melanogenesis)

f. Race

g. Nutrition

h. Metabolism

i. Sunlight

C. Pathophysiology

1. Epidermal type: melanin is deposited in the basal and suprabasal layers of the epidermis.

2. Dermal type: melanophages in the superficial and deep dermis in addition to epidermal hyperpigmentation.

D. Incidence

1. Unknown true incidence.

2. Almost 90% affected are women.

3. More common in persons of Latino origin living in tropical areas.

4. Commonly seen in women who are pregnant or using oral contraceptives or hormonal replacement.

5. Is seen in men, but usually without hormonal factors.


II. ASSESSMENT

A. History: always take a complete history.

B. Clinical manifestations

1. Symmetrical

2. Irregular light to dark-brown hyperpigmentation

3. Seen on the face

a. Centrofacial

(1) Most common presentation

(2) Involves cheeks, forehead, upper lip, nose, and chin

b. Malar

(1) Localized to cheeks and nose

(2) Second most common presentation

c. Mandibular

(1) Involves the ramus of the mandible

(2) Least common presentation

4. Four types (distinguished with the use of Wood light according to the depth of pigment deposition)

a. Epidermal: shows enhancement of pigmentation (most common type intense under Wood lamp).

b. Dermal: no enhancement of color (many melanophages) in the dermis.

c. Mixed: shows no or slight enhancement of color.

d. Indeterminate or unapparent—lesions are not discernible under Wood light in skin types V to VI.

5. Differential diagnosis (partial list)

a. Drug-induced hyperpigmentation

b. Pigmented contact dermatitis

c. Postinflammatory hyperpigmentation

d. Exogenous ochronosis (blue-black or slate gray hyperpigmented changes secondary to prolonged topical application of hydroquinone, phenol, or resorcinol)


III. COMMON THERAPEUTIC MODALITIES

A. Identify and eliminate causative factors.

B. Medications

1. Hydroquinone alone (2% to 4% concentrations most commonly used)

2. Hydroquinone with retinoic acid (retinoic acid enhances epidermal penetration of hydroquinone and reduces the activity of the melanocytes)

3. Broad-spectrum sunscreen

4. Topical steroids (alone or in conjunction with hydroquinone, or hydroquinone plus retinoids)

5. 5-Fluorouracil (effective particularly if patients have actinically damaged skin)


6. Azelaic acid (causes reversible inhibition of tyrosinase; may be used in conjunction with hydroquinone)

C. Possible side effects of topical medications

1. Hydroquinone therapy

a. Irritant contact dermatitis

b. Exogenous ochronosis

c. Brown discoloration of nails secondary to deposition of hydroquinone oxidated products

d. Vitiligo in predisposed individual

2. Topical steroids: hypopigmentation, atrophy

D. Chemical peel (trichloroacetic acid or phenol solution). Phenol peels can cause cardiac, renal, and pulmonary toxicities.

E. Lasers (Q-switched, fractionated nonablative)


CHEMICALLY INDUCED HYPERPIGMENTATION


I. OVERVIEW

Hyperpigmentation has long been associated with exposure to a variety of chemicals.

A. Definition: unusual darkening of the skin as a direct result of exposure to chemicals

B. Etiology

1. Direct deposition of the chemical into the skin.

2. Stimulation of melanin formation.

3. Binding of chemical to melanin.

4. Production of metabolites or nonmelanin pigment.

5. Hyperpigmentation may be enhanced by exposure to ultraviolet light.

6. Offending agents

a. Antimalarials

b. Antibiotics

c. Heavy metals, such as silver

d. Chemotherapeutic agents

e. Topical preparations (e.g., tar-containing compounds)

f. Antiarrhythmic, amiodarone

C. Pathophysiology

1. Dependent on etiologic agent.

2. Antimalarials: hyperpigmentation appears in the dermis; may be a combination of melanin and hemosiderin.

3. Antibiotics: pigmentation depends on presentation; minocycline is used as an example here.

a. In areas of scarring, such as acne scars, hemosiderin and ferritin are present in macrophages and appear blue-black.

b. Blue-black, brown, or slate gray patches on extremities have pigmented macrophages that stain for both melanin and iron.

c. Generalized muddy-brown pigmentation sometimes exacerbated on sunlight-exposed regions.


II. ASSESSMENT

A. History with emphasis on chemical exposure

B. Physical examination

C. Clinical manifestations

1. May vary, as described.

2. Skin biopsy may be indicated to confirm diagnosis.


III. COMMON THERAPEUTIC MODALITIES

A. Often persistent.

B. Stop offending agent or exposure if known (particularly drug).

C. Prevent recurrent exposure.

D. Use sunscreens.


NEVI


MELANOCYTIC NEVI


I. OVERVIEW

Nevi, or moles, are benign tumors composed of nevus cells that are derived from melanocytes and can occur anywhere on the cutaneous surface, and except for certain types (large congenital and dysplastic), most nevi have low-malignancy potential.

A. Definition

1. Nevus cell: larger than melanocyte, may lack dendrites; has more abundant cytoplasm and coarse granules; aggregates in groups or proliferates in basal region at dermoepidermal junction

2. Types of nevi (Table 17-1)

a. Common nevi: classified based on location within the skin

(1) Junction

(2) Compound

(3) Intradermal

b. Special forms

(1) Congenital (Figure 17-6)

(2) Halo nevus (Figure 17-7)

Only gold members can continue reading. Log In or Register to continue

Mar 9, 2021 | Posted by in NURSING | Comments Off on Disorders of Pigmentation and Dermatologic Considerations in Ethnic Skin
Premium Wordpress Themes by UFO Themes