The Newborn Infant
An infant is admitted to the normal newborn nursery. He was born vaginally at 38 weeks' gestation to a 33-year-old woman with limited prenatal care. On physical examination weight, height, and head circumference are less than the 10th percentile. He is somewhat irritable with good tone and cry. In addition to the findings shown (Photograph) he has strabismus and abnormal palmer creases. On echocardiogram he has a ventricular septal defect. Which of the following is the most likely mechanism for this condition?
a. Exposure in utero to phenytoin
b. Translocation of chromosome 21 genetic material
c. Pathogenetic mutation of the COL4A5 genes on the X chromosome
d. Exposure in utero to ethanol
e. Exposure in utero to maternal hyperglycemia
The answer is d. (Hay et al, pp 102-103. Kliegman et al, pp 625-626. McMillan et al, p 263. Rudolph et al, p 738.) Fetal alcohol syndrome is caused by prenatal exposure to ethanol. Findings include small-for-gestation birth, microcephaly, small palpebral fissures, short nose, smooth philtrum, thin upper lip, ptosis, strabismus, microphthalmia, and central nervous system abnormalities including mental retardation. Cardiac defects, particularly septal defects, are commonly seen.
Common findings with trisomy 21 include protruding tongue, Brushfield spots, redundant neck skin, mental retardation, brachycephaly, upslanting palpebral fissures, epicanthal folds, flat face, small ears, cardiac abnormalities (especially ventricular septal defect or endocardial cushion defect), palmar creases, and clinodactyly of the fifth digit.
Dilantin exposure causes midface hypoplasia, low nasal bridge, ocular hypertelorism, and accentuated Cupid's bow of the upper lip. Other features include cleft lip and palate, growth retardation, mental deficiency, distal phalangeal hyperplasia, cardiovascular anomalies, and skeletal defects.
Alport syndrome is the most common of the hereditary nephritis conditions, frequently leading to end-stage renal disease. In 85% of patients with Alport syndrome, an X-linked dominant form (pathogenic mutation of the COL4A5 gene on the X chromosome) of inheritance is found; about 15% are autosomal recessive (due to pathogenic mutations of the COL4A3 or 4 genes on chromosome 2). All cause hematuria and progressive nephritis. Other findings include deafness and ocular defects.
Infants of diabetic mothers have an increased chance of congenital heart disease, caudal regression syndrome, and a small left colon. They are large-for-gestational age and frequently have a number of biochemical abnormalities such as hypoglycemia and hypocalcemia.
A 3-day-old neonate is seen by the pediatrician for early follow-up after birth. The boy was born vaginally at term to a 31-year-old woman whose pregnancy was complicated by seizures which were well controlled with phenobarbital. The newborn has been bottle-feeding well, and ...