Definition Various regionally limited congenital alterations of skin pigmentation or skin color are referred to as birthmarks. They may not be observed at birth, but usually they are obvious by several months of age. They can be due to the presence of an increased number of superficial lymph or blood vessels, increased pigment in the epidermis, aberrant tissue present in the skin, or pigment variation in the dermis.
Local Variations in Pigmentation
Café au Lait Spot Macular are of increased pigment:
• Size, a few millimeters to many centimeters
• Frequency, 5 percent of the population
• Localization, all body areas
• Origin, local melanocyte activity
• Remarks, may be a sign of neurofibromatosis if more than five café au lait spots greater than 0.5 cm before puberty or 1.5 cm after puberty are present
Blue Nevus Bluish macular area:
• Size, usually larger than 5 cm
• Synonym, blue nevus; the blue color is an optical effect of deep-seated melanin
• Frequency, 9.6 percent in Caucasians, 95.5 percent in African Americans, 81 percent in Asians
• Localization, primarily over the sacrum and the gluteal region
• Origin, ectopic melanocytes in the dermis
• Remarks, no pathological significance; can be present from the fifth gestational month and usually disappears during childhood because of the loss of dermal pigment
Depigmentation Macular area of reduced pigment:
• Frequency, 1 percent of the population
• Localization, can occur limited to circumscribed body areas or with a patchy distribution
• Origin, lack of functional melanocytes in this area
• Remarks, multiple small, leaf-shaped depigmented areas may be a sign of tuberous sclerosis
Mole Circumscribed area of dark pigment:
• Synonym, lentigo, compound nevus
• Frequency, very common
• Localization, all body parts, usually present at birth but may occur later
• Color, varies from dark brown to black
• Shape, may be flat, elevated, verrucoid, domeshaped
• Origin, proliferation of melanocytes
Local Variation of Vasculature Pink macular area, commonly on the nape of the neck, eyelids, glabella, and midforehead in newborns:
• Synonyms, Unna's mark, nevus simplex, erythema nuchae, angel's kiss, salmon patch
• Size, very small fleck to several centimeters
• Frequency, very common; may be obvious at birth or appear within the first few days; persists throughout life but becomes less obvious with age
• Origin, dermal capillaries or telangiectases, representing fetal circulatory patterns in the skin
Elevated Vascular Nevus Elevated irregular lesion of solid red color:
• Synonym, strawberry nevus, cavernous hemangioma, capillary hemangioma
• Frequency, 10 percent of the population
• Localization, single or multiple, all body areas
• Origin, enlarged or dilated vessels of the skin (nevus vascularis). Thrombosis may occur inside the nevus, which may resolve spontaneously, but rarely it may require therapeutic intervention, especially if a vital function or vision is disturbed.
• Remarks, usually not present at birth, but appears in the first few months of life, enlarging during the first year and then most often resolving spontaneously.
Port Wine Nevus Large dark angioma; may start as pink-colored macula that later becomes purple and may be raised; at first it may be smooth but can become irregular later.
• Synonym, nevus flammeus
• Frequency, 0.3 percent of the population
• Localization, any area of the body, but usually anterior or lateral, not posterior; most frequently unilateral and rarely crosses the midline
• Origin, dilated mature capillaries of the dermis
• Remarks, can be a sign of Sturge-Weber syndrome if in the distribution of the first branch of the trigeminal nerve; does not resolve spontaneously.
Telangiectasia Prominent blood vessel on the surface of the skin.
• Origin, results from a widening of the capillaries
• Localization, the main location is on the nose, the upper lip, conjunctiva, and the cheeks
• Remarks, the number increases with age; it can be seen in the ataxia-teleangiectasia syndrome and in hereditary hemorrhagic teleangiectasia
Lymphangioma Overgrowth of lymphatic vessels.
• Synonym, cystic hygroma
• Localization, mostly found in the neck and tongue area
• Origin, results from lymphatic vessel anomalies
• Remarks, can lead to an excess of skin in the neck area when it occurs prenatally and subsequently resolves
Other Anomalies of the Skin
Nevus Sebaceous Raised waxy patch, often linear.
• Synonym, Jadassohn nevus
• Origin, organoid nevus of the epidermis with a preponderance of sebaceous glands
• Frequency, 0.2 percent of the population
• Localization, frequently on scalp or head
• Remarks, may be associated with mental retardation and seizures; may be seen in Proteus syndrome
Cutis Aplasia Area of absence of skin:
• Frequency, rare, less than 0.1 percent
• Localization, usually in the midline at the vertex of the scalp
• Origin, possibly due to a vascular accident during development in utero. The area of the scalp in which it occurs most frequently is the spot from which the skin stretches when it grows and may be the first point to break down during abnormal development
• Remarks, frequent in trisomy 13, and Adams-Oliver syndrome
Dimple Area in which the skin is attached to underlying structures:
• Localization, frequently over knuckles and on cheeks; occasionally at ankles, knees and elbows; rarely over buttocks or sacrum
• Origin, occurs in areas where there is unusually close proximity between bone, joints, or muscle and the skin during fetal life
Congenital Alopecia Patch of skin without hair growth:
• Localization, may occur anywhere on the scalp or body
• Origin, absence or loss of hair follicles that may result from failure of hair follicles to develop or from follicles that produce a decreased amount of hair.
Chapter 11 Skin and Hair Glands of the Skin Introduction
There are two kinds of glands in the skin: the sebaceous glands and the sweat glands (Fig. 11.3). Most sebaceous glands develop along the side of a developing epithelial root sheath of a hair follicle. A glandular bud grows
Figure 11.3 Development of sweat glands and sebaceous glands and the hair shaft. From Moore (1982), by permission.
Hair bud Mesenchyme
.Epidermis Stratum germinativum Bud
.Epidermis Stratum germinativum Bud
12 weeks of gestation
Hair bud Mesenchyme
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