QUESTION 20
At 24 hours after birth, a term male infant is noted by his mother to have muscular spasms. A physician is called, who orders stat testing for calcium. The calcium concentration is low. Following the resolution of the muscular spasms, an echocardiogram is performed, which reveals a ventricular septal defect. Flow cytometric analysis of the blood would reveal a decreased concentration of which of the following cell types?
A. B lymphocytes
B. T lymphocytes
C. Monocytes
D. Eosinophils
E. Neutrophils
Answer for Question 20
Answer: B (T lymphocytes)
Explanation: Hypocalcemic tetany (i.e., the muscular spasms) presenting shortly after birth is one feature of DiGeorge syndrome. Another feature is congenital heart disease, which can include several conditions, of which a ventricular septal defect is one. DiGeorge syndrome will produce a T cell deficiency, but does not affect the other cell types of the immune system.
QUESTION 21
A 15-year-old female has had one to five episodes of otitis media each year for the past several years, and at least one episode of severe pneumonia each year, some requiring hospitalization. Laboratory testing reveals an increased number of B cells. Her past medical history otherwise only includes a fracture of her right radius sustained while snowboarding. A biopsy of a lymph node reveals hyperplastic follicles. Of the following, which cell type would not be present in the lymph node?
A. Macrophages
B. B lymphocytes
C. T lymphocytes
D. Dendritic cells
E. Plasma cells
Answer for Question 21
Answer: E (plasma cells)
Explanation: given the history of recurrent otitis media and pulmonary infections occurring in an adolescent female, common variable immunodeficiency is a likely diagnosis. In this disease process, B cells are produced; however, they do not differentiate into plasma cells, and patients are hypogammaglobulinemic. In the normal lymph node, all of the above cell types are present; however, as patients with common variable immunodeficiency do not produce plasma cells, they would not be identified in a biopsy from this patient.
QUESTION 22
A 7-month-old male is brought to the emergency room by his parents. Over the past two days he has been coughing and today he was feeding less than normal. His temperature taken with a thermometer at home was 101 degrees Fahrenheit. A CT scan reveals consolidation of the lower lobe of the left lung, but no enlarged hilar lymph nodes. Laboratory testing for immunoglobulins reveals an absence of IgG, IgA, and IgM. Of the following, what additional finding would be identified during the physical examination?
A. Thymic hyperplasia
B. A nodule in the thyroid gland
C. Very small tonsils
D. Hypertrophy of the tongue
E. Palpable parathyroid glands
Answer for Question 22
Answer: C (very small tonsils)
Explanation: the patient has X-linked (Bruton’s) agammaglobulinemia, which presents in males after the age of 6 months. Patients develop recurrent lung and sinus infections, most commonly with encapsulated organisms. The laboratory diagnosis is made by confirming very low levels of immunoglobulins and absence of B cells in the blood. In addition to an inability to develop lymph nodes, patients will often have very small tonsils. The other conditions listed are not characteristically associated with X-linked agammaglobulinemia.