Birthmark is a term that describes congenital anomalies of the skin. It should not be used as a definitive diagnosis because congenital skin lesions vary greatly in their appearance and prognosis. The differential diagnosis of various birthmarks is listed in Table 193-1.
The most frequently encountered pigmented lesion is dermal melanosis, which occurs in 70% to 90% of African-American, Hispanic, Asian, and Native American infants and in approximately 5% of white infants. This is a congenital lesion caused by entrapment of melanocytes in the dermis during their migration from the neural crest into the epidermis. Although most of these lesions are found in the lumbosacral area (Mongolian spot), they also occur at other sites such as the buttocks, flank, extremities, or, rarely, the face (Fig. 193-1). Single or multiple, poorly demarcated, gray-blue patches up to 10 cm in size may be present. Most lesions gradually disappear during the first few years of life; aberrant lesions in unusual sites are more likely to persist.
Café au lait macules are pigmented macules or patches, whichmay be present in a newborn but tend to develop during childhood (Fig. 193-2). They range in color from very light brownto a chocolate brown. Up to five café au lait macules are foundin 1.8% of newborns and 25% to 40% of normal children, and have no significance. Children with six or more café au laitmacules (0.5 cm in diameter before puberty or greater than 1.5 cm in diameter after puberty), especially when accompaniedby axillary or inguinal freckling, should be evaluated carefully
Brown (<20 cm)/plaque Congenital melanocytic nevus Variable Low risk of melanoma
Brown (>20 cm)/plaque Giant congenital melanocytic Trunk most common Risk of melanoma and nevus
Brown-“flesh-colored”/plaque Epidermal nevus Variable, trunk and neck May enlarge with time
Red/patch Port-wine stain (nevus flammeus) Variable, face most common May be associated with Sturge-Weber syndrome
Red/patch Salmon patch (nevus simplex) Glabella, eyelids, nape of neck Improves or resolves with time
Red/papule or plaque Hemangioma Variable May be associated with liver hemangiomas, airway hemangiomas, and PHACE syndrome
Blue-purple/nodule Cephalohematoma Scalp Resolves with time
Blue-purple/plaque Venous, lymphatic, or mixed Variable Intermittent swelling and pain malformation
Hypertrichosis/tumor Plexiform neurofibroma Trunk most common Associated with neurofibromatosis type 1 for additional stigmata of neurofibromatosis type 1. Other disorders also associated with café au lait macules include the other forms of neurofibromatosis, Legius syndrome, tuberous sclerosis, McCune-Albright syndrome, multiple lentigines/LEOPARDsyndrome, Noonan syndrome, and Russell-Silver syndrome.
Figure 193-1 Dermal hypermelanosis (back).
Figure 193-2 Cafe au lait spots (leg).