๐ ็ธฝ็ฎ้ ๏ฝ ๐ ่ฑๆๅๆ๏ผๆฌ็ฏ๏ผ ๏ฝ ๐ ๅฎๆด็ฟป่ญฏ ๏ฝ โญ ็ฒพ่ฏ็ญ่จ
INTRODUCTION
Developmental anomalies are a diverse group of congenital disorders that result from faulty morphogenesis. They include both malformations, defined as structural defects arising due to errors in embryologic development, and disruptions, which occur when a structure programmed to develop normally is damaged before it is fully formed. A classic example of the former is incomplete closure of the neural tube resulting in an encephalocele, while the latter process is illustrated by the anomalies associated with varicella embryopathy. Although developmental anomalies that affect the skin are often recognized at birth or during infancy, occasionally diagnosis is delayed until later in life. The cutaneous abnormalities range in severity from isolated, minor physical findings (e.g. rudimentary supernumerary digits) to deforming, potentially life-threatening defects (e.g. deep, irregular scalp aplasia cutis congenita in AdamsโOliver syndrome). Furthermore, some skin lesions that appear to be innocuous may serve as important clues to the presence of a multiple congenital anomaly syndrome or, particularly when involving the midline, the existence of a serious defect of the underlying tissues. Such associations reflect the complex interactions between various ectodermal and mesodermal elements that occur during the intricate processes of morphogenesis and differentiation.
This chapter begins with an overview of the midline lesion and its relationship to closure of the neural tube. A discussion of specific issues pertaining to midline lesions of the nose, scalp, and spine follows, including a review of the different types of anomalies that can present in these sites. An overview of aplasia cutis congenita is followed by
Richard J. Antaya and Julie V. Schaffer
presentation of a clinical approach based on the morphology and distribution of lesions and the presence or absence of associated abnormalities. Finally, a variety of non-midline developmental anomalies are discussed, including lip pits, accessory tragi, supernumerary nipples, skin dimples, malformations of the dermatoglyphics, rudimentary supernumerary digits, and the amniotic band sequence. Developmental anomalies that are covered in Chapter 110 include ear pits as well as branchial cleft, thyroglossal duct, bronchogenic, median raphe, omphalomesenteric duct, and urachal cysts.