An autopsy is performed on an 8-month-old infant after his unexpected death. Prior to death, the patient had a 1-month history of poor feeding and intermittent fever, which progressed to severe lethargy and coma. The infant was adopted soon after birth, and there is limited information about his family history beyond documentation of an uncomplicated pregnancy and delivery at term gestation. Brain biopsy reveals leptomeningeal inflammation and is positive for Enterovirus by PCR. This patient would have been most likely to have which of the following laboratory findings?

Question

An autopsy is performed on an 8-month-old infant after his unexpected death.  Prior to death, the patient had a 1-month history of poor feeding and intermittent fever, which progressed to severe lethargy and coma.  The infant was adopted soon after birth, and there is limited information about his family history beyond documentation of an uncomplicated pregnancy and delivery at term gestation.  Brain biopsy reveals leptomeningeal inflammation and is positive for Enterovirus by PCR.  This patient would have been most likely to have which of the following laboratory findings?

Quizplus · Accepted Answer

11ec160b_37c5_96d5_9249_11337bbb8c1d_MD0001_00 Enterovirus is a common infection in children that typically causes self-limited disease, such as herpangina, hand-foot-and-mouth disease, or in some cases, aseptic meningitis. However, because neutralizing antibodies are required to clear Enterovirus, severe life-threatening infection can occur in infants with a primary humoral immunodeficiency such as X-linked agammaglobulinemia (XLA). XLA, or Bruton agammaglobulinemia, is due to a mutation in the BTK gene encoding Bruton tyrosine kinase. A defect in this protein prevents pre-B cells from differentiating and exiting the bone marrow. Therefore, patients have low circulating B lymphocytes and low immunoglobulin levels. In addition to enteroviral infection, XLA also increases the risk for recurrent sinopulmonary infections by encapsulated bacteria (eg, Streptococcus pneumoniae, Haemophilus influenzae type b), which require antibody opsonization for phagocytosis. Patients with impaired humoral immunity are also predisposed to gastrointestinal infections (eg, Salmonella, Campylobacter), as well as chronic giardiasis (due to low secretory IgA). (Choice A) An abnormal dihydrorhodamine test indicates an impaired neutrophil respiratory burst, which occurs in chronic granulomatous disease. Patients have recurrent skin and pulmonary infections with catalase-positive organisms (eg, Staphylococcus aureus, Serratia marcescens). Severe enteroviral infections are not seen. (Choice B) Absent peripheral neutrophils, as seen with acquired or congenital neutropenia, increase the risk of bacterial (eg, Staphylococcus aureus) and fungal (eg, Candida) infections. Neutrophils have little role in eradicating viruses. (Choice C) Eosinophils are involved in atopic disease and defense against parasitic infections. Lack of tissue eosinophils is not associated with severe, chronic viral infections. (Choice D) Total hemolytic complement (CH50) measures the serum's ability to lyse sheep erythrocytes coated with IgM antibody. A normal CH50 requires intact activity of all components of the classical complement pathway (C1-C9). Complement deficiency most often predisposes to autoimmunity (eg, systemic lupus erythematosus) or infection with encapsulated bacteria (eg, Neisseria). (Choice F) IgG2 is primarily responsible for opsonization of encapsulated bacteria. IgG2 subclass deficiency typically presents with frequent respiratory infections, not enteroviral meningitis, and the clinical course is generally less severe than with XLA. Educational objective: X-linked agammaglobulinemia, an immunodeficiency characterized by low circulating B lymphocytes and immunoglobulins, should be suspected in an infant with severe, life-threatening enteroviral infection.

An Autopsy Is Performed on an 8-Month-Old Infant After His