The mandibular region is the area from the lower portion of the ears bounded out to the chin by the mandible. In most newborns, the chin is often slightly retruded (that is, slightly behind the vertical line extending from the forehead to the philtrum). If this retrusion is pronounced, the child may have the Pierre Robin malformation sequence. In addition, the mouth should be examined. The number and appearance of the teeth should be noted, the tongue should be observed for abnormalities, and the palate and uvula checked for defects.
Examination of the neck may reveal webbing, a common featurein Turner syndrome and Noonan syndrome, or shortening, as isseen occasionally in some skeletal dysplasias and in conditions inwhich anomalies of the cervical spine occur, such as Klippel-Feilsyndrome. The position of the posterior hairline also should beevaluated. The size of the thyroid gland should be assessed.
The chest may be examined for shape (shield-like chest in Noonan syndrome and Turner syndrome) and for symmetry. The presence of a pectus deformity should be noted and is common in Marfan syndrome. The presence of scoliosis should be assessed; it is common in Marfan syndrome and many other syndromes.
Many congenital malformation syndromes are associated withanomalies of the extremities. All joints should be examined forrange of motion. The presence of single or multiple joint contractures suggests either intrinsic neuromuscular dysfunction, as insome forms of muscular dystrophy, or external deforming forcesthat limited motion of the joint in utero. Multiple contracturesalso are found with arthrogryposis multiplex congenita and are due to a variety of causes. Radioulnar synostosis, an inability topronate or supinate the elbow, occurs in fetal alcohol spectrumdisorder and in some X chromosome aneuploidy syndromes.
Examination of the hands is important. Polydactyly (the presence of extra digits) usually occurs as an isolated autosomal dominant trait but also can be seen in trisomy 13.Oligodactyly (a deficiency in the number of digits) is seenin Fanconi syndrome (anemia, leukopenia, thrombocytopenia, and associated heart, renal, and limb anomalies—usuallyradial aplasia and thumb malformation or aplasia), in whichit is generally part of a more severe limb reduction defect, orsecondary to intrauterine amputation, which may occur withamniotic band disruption sequence. Syndactyly (a joining of two or more digits) is common to many syndromes, including Smith-Lemli-Opitz syndrome (see Chapters 199 and201).
Dermatoglyphics include palmar crease patterns. A transverse palmar crease, indicative of hypotonia during early fetal life, is seen in approximately 50% of children with Down syndrome (and 10% of individuals in the general population). A characteristic palmar crease pattern is also seen in fetal alcohol spectrum disorder.
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Genitalia should be examined closely for abnormalities in structure. In boys, if the penis appears short, it should be measured and compared with known age-related data. Ambiguous genitalia often are associated with endocrinologic disorders, such as congenital adrenal hyperplasia (girls have masculinized external genitalia, but male genitalia may be unaffected), or chromosomal disorders such as 45,X/46,XY mosaicism or possibly secondary to a multiple congenital anomaly syndrome (see Chapters 174 and 177). Although hypospadias, which occurs in 1 in 300 newborn boys, is a common congenital malformation that often occurs as an isolated defect, if it is associated with other anomalies, especially cryptorchidism, there is a strong possibility of a syndrome.