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Congenital adrenal hyperplasia (CAH) is due to enzymatic defects which impair the synthesis of cortisol and, frequently, aldosterone. CAH varies in its clinical presentation and severity. At birth, most males with CAH will appear normal. Some females with CAH will appear virilized. The most severe cases of CAH are associated with adrenal crisis and salt-wasting crisis. CAH due to 21-hydroxylase deficiency accounts for 95% of cases of CAH. Infants with CAH due to 21-hydroxylase deficiency have elevated 17-hydroxyprogesterone levels. The newborn screen tests for elevated 17-hydroxyprogesterone levels. A "presumptive positive screen for CAH" strongly suggests that the infant has CAH due to 21-hydroxylase deficiency.
You should immediately have the infant seen by a physician to look for signs and symptoms of adrenal insufficiency and salt wasting, such as lethargy, poor feeding, vomiting, hypotension, and dehydration. Infants with CAH may also be virilized and have acne, axillary hair, pubic hair, clitoromegaly, and/or ambiguous genitalia.
You should check a basic metabolic panel to assess for hyponatremia, hyperkalemia, acidosis, and hypoglycemia, which can be associated with adrenal insufficiency and salt wasting. You should also check a plasma 17-hydroxyprogesterone level to confirm the diagnosis. You should send this sample to a clinical laboratory to obtain an accurate value rather than sending the sample again to the newborn screening lab.
Infants with salt wasting CAH can appear normal and have normal electrolytes at birth. However, they can develop a salt-wasting crisis up to a few weeks after birth. Until the result for the plasma 17-hydroxyprogesterone level returns normal, the infant will need close clinical follow-up and monitoring of serum electrolytes.
You should act in a similar manner as if the result was a "presumptive positive".
If the infant has an abnormal screen for and any signs or symptoms suggestive of adrenal insufficiency, salt wasting, or virilization, contact the pediatric endocrinologist immediately for advice. The infant may need emergent saline and glucocorticoids to treat life threatening adrenal crisis and salt wasting crisis.
Francis Hoe, MD
Barbara Davis Center for Childhood Diabetes