Aplasia cutis congenita This not uncommon disorder is characterized by congenital localized areas of missing skin. These may present as ulcers, or may have already healed by the time of birth. The most common location is the vertex of the scalp. Figure 30-1 depicts a child born with superficial erosion.

Shown in Fig. 30-2 is a child with a significant ulcer as a presentation of aplasia cutis congenita. Lesions of this type inevitably heal with scarring, and with an area of alopecia. Most infants have a single lesion, although multiple lesions may occur.

Aplasia cutis congenita Although the occurrence of this condition is usually an isolated event, it may be seen in a number of syndromes. In Adams-Oliver syndrome, distal limb reduction abnormalities are found in association with solitary midline scalp defects. SCALP syndrome is the constellation of nevus Sebaceus, Central nervous system malformations, Aplasia cutis congenita, Limbal dermoid, and Pigmented nevus.

This radiograph represents a case of aplasia cutis congenita associated with a significant underlying skull defect. When this occurs, there is a higher risk of infection and bleeding. These smaller bony defects usually heal in a few months. The larger lesions may require neurosurgical repair.

Aplasia cutis congenita Sometimes a thicker, darker growth of hair may be seen around the lesion of aplasia cutis congenita on the scalp. The “hair collar sign” may be a marker for cranial dysraphism such as encephalocele, agenesis of the corpus callosum, and heterotopic brain tissue. This may be a forme fruste of a neural tube defect.

Figures 30-5 and 30-6 show a membranous variety of aplasia cutis congenita. Although lesions of this type may be mistaken for bullae, the location and hair collar signify that this is a defect of skin closure covered by a thin membrane.

Aplasia cutis congenita Seen in Fig. 30-7 is another infant with a “hair collar” sign. In this patient, there is aplasia cutis congenita with both a vascular stain and a whorl of hair. This combination of cutaneous findings might raise particular concern about an underlying abnormality and should prompt appropriate imaging of the brain.

This is an example of a lesion of aplasia cutis congenita that has healed into a scar. This process may occur in utero or shortly after birth. Figure 30-8 pictures a lesion that healed postpartum. Note that the defect involved the full thickness of skin and resulted in destruction of the hair bulbs. In consequence, the scar, healed by secondary intention, is bald and may require plastic surgery in the future.

Fetus papyraceus A particular variant of aplasia cutis congenita results from the in utero demise of a twin. Affected infants have symmetric “butterfly-shaped” involvement of the trunk and sometimes fibrous bands encircling the extremities. The remains of the twin fetus (“fetus papyraceus”) may be embedded in the placenta.

The skin abnormalities that occur in the surviving infant may be result of disseminated intravascular coagulation. Additional findings in such patients include clubbing of the hands and feet, nail dystrophy, and developmental delay, sometimes accompanied by spastic paraparesis.

Aplasia cutis congenita limited to legs and feet In some infants, the occurrence of aplasia cutis congenita which is limited to the distal lower extremities is a presenting sign of epidermolysis bullosa. In other patients, it is benign and not associated with a genetic blistering disorder.

Supernumerary digits Supernumerary digits, such as other supernumerary structures, come in all degrees of development, from merest suggestion to nearly full reduplication. Figure 30-12 shows a fairly well-developed extra digit containing bones, musculature, and nerves and situated in a common site just beyond the last natural finger. More commonly, the vestige consists of a small nubbin of soft tissue in the same location. Treatment is by surgical excision.

Amputation neuroma Although surgical removal of a supernumerary digit is a technically simple operation, a rare complication is illustrated in Fig. 30-13. It is an amputation neuroma, a knot of neural tissue formed at the site of the wound of an operation for removal of a structure that had nerves within it. Such a lesion can be tender to touch, spontaneously painful, and possibly productive of phantom symptoms. Reexcision is necessary.

Supernumerary nipple Supernumerary nipples are exceedingly common in both sexes. In women, more than mere nipples, considerable mammary glands may develop along the “milk lines” from axillae to pubes. In males, one or a pair of supernumerary nipples is common enough; two, even three, complete pairs are still not rare. The degree of development may be from vestiges that could be taken for common pigmented moles to well-developed ones like those pictured in Fig. 30-14.

Auricular tags Supernumerary vestiges of the external structures of ears are common. Accessory tragi and auricular tags with or without communication to deeper structures may be deceptively simple.

Sometimes, however, such structures bear cartilage within them and communicate with the more important structures in the external canal or middle ear.

Auricular tag In Fig. 30-17 there is a bit of reduplicated auricular tissue that had been displaced onto the neck. Again, the anomalous tissue could be easily excised if it had no communication deeper and upward. In the latter event, more thorough dissection of the entire structure would be required.

Dental sinus Infection at or around the apex of a tooth may become an abscess that drains in the overlying skin. There may be a channel from a tooth in the lower jaw onto the skin over the mandible, on the underside of the chin or jaw, or on the neck. The presenting lesion may appear, like the one pictured in Fig. 30-18, as a superficial pyoderma, or an infected cyst. Excision of the entire lesion is required.

Branchial-cleft cysts The embryogenesis of the head and neck requires that many structures have to come together perfectly from both sides. An occasional failure of perfect coaptation is to be expected. Cleft palate and cleft lips are well known and easily recognizable. More subtle is failure of perfect development of the branchial arches.