A 7-day-old boy is admitted to a hospital for evaluation of vomiting and dehydration. Physical examination is otherwise normal except for minimal hyperpigmentation of the nipples. Serum sodium and potassium concentrations are 120 meq/L and 9 meq/L, respectively; serum glucose is 120 mg/dL. Which of the following is the most likely diagnosis?

a. Pyloric stenosis

b. Congenital adrenal hyperplasia

c. Secondary hypothyroidism

d. Panhypopituitarism

e. Hyperaldosteronism

the answer is below…

The United States Medical Licensing Examination, or USMLE for short, is a three-part licensing examination that is required in order to receive a license to practice medicine within the United States.

The USMLE assesses a physician’s ability to apply knowledge, concepts, and principles, and to determine fundamental patient-centered skills that are important in health and disease and that constitute the basis of safe and effective patient care.Examination committees composed of medical educators and clinicians from across the United States and its territories prepare the examination materials each year.

This exam is designed by the Federation of State Medical Boards and the National Board of Medical Examiners to determine whether or not an individual understands and can apply the knowledge necessary to practice medicine safely and intelligently.

The USMLE is actually comprised of three different exams that are referred to as steps, which examine the individual’s knowledge of specific topics related to the field of medicine such as basic science, medical knowledge, medical skills, clinical science, and the application of all of these skills and areas of knowledge in the medical field.

All three steps of the USMLE include a series of computerized multiple-choice questions, but the format of the exam and the information covered in each multiple-choice section is different for each step of the USMLE. The USMLE Step II also has a clinical skills portion that examines an individual’s ability to work with real patients and the USMLE Step III has a computerized patient simulation portion in addition to the multiple-choice section of the exam. In order for an individual to receive a license to practice medicine, the individual must pass all three steps of the USMLE.

Medical doctors with an M.D. degree are required to pass this examination before being permitted to practice medicine in the United States of America

The correct answer is b; Congenital adrenal hyperplasia.[1]

Salt-losing congenital adrenal hyperplasia (adrenogenital syndrome, 21-hydroxylase deficiency) usually manifests during the first 5 to 15 days of life as anorexia, vomiting, diarrhea, and dehydration. Hypoglycemia can also occur. Affected infants can have increased pigmentation, and female infants show evidence of virilization, that is, ambiguous external genitalia. Hyponatremia, hyperkalemia, and urinary sodium wasting are the usual laboratory findings. Death can occur if the diagnosis is missed and appropriate treatment is not instituted.

Although adrenal aplasia, an extremely rare disorder, presents a similar clinical picture, it has an earlier onset than adrenal hyperplasia, and virilization does not occur. In classic 21-hydroxylase deficiency, serum levels of 17-hydroxyprogesterone are markedly elevated beyond 3 days of life (in the first 3 days of life they can normally be high). Blood cortisol levels are usually low in salt-losing forms of the disease.

Pyloric stenosis seems unlikely in this infant in that the vomiting with this disease usually begins after the third week of life. Hypothyroidism would present as a lethargic, poor-feeding infant with delayed reflexes, persistent jaundice, and hypotonia. Hyperaldosteronism would be expected to cause decreased potassium, not increased levels. Panhypopituitarism usually presents with apnea, cyanosis, or severe hypoglycemia.