An 18-year-old woman is brought to the emergency department with severe abdominal pain. Medical history includes asthma, eczema, and multiple episodes of pneumonia. Her temperature is 37.2 C (99 F), blood pressure is 90/60 mm Hg, and pulse is 128/min. Physical examination shows pallor and a tender, rigid abdomen. Laboratory studies reveal a hemoglobin concentration of 6.9 mg/dL and platelet count of 378,000/mm³. Emergency laparotomy reveals a ruptured ectopic pregnancy. The patient receives a transfusion with blood type O, Rh-negative, packed red blood cells. During the transfusion, she experiences generalized hives and a drop in blood pressure to 70/40 mm Hg. The transfusion is stopped and intramuscular epinephrine is administered. Which of the following is the most likely diagnosis?

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11ec25c8_d629_245b_bc81_a1d89c91bcf8_MD0003_00 This patient has a history of recurrent pneumonia, atopy (eg, asthma, eczema), and an anaphylactic reaction during blood transfusion. These findings are highly suggestive of selective IgA deficiency, the most common primary immunodeficiency. Serum IgA levels are low or undetectable due to failure of B cells to differentiate into IgA-secreting plasma cells; serum IgG and IgM levels are normal. Although most patients with IgA deficiency are asymptomatic, some have recurrent sinopulmonary (eg, sinusitis, pneumonia) and gastrointestinal infections (eg, Giardia) due to absence of secretory IgA as a mucosal barrier. Concomitant atopic and autoimmune disorders (eg, systemic lupus erythematosus, celiac disease) are common. Patients with severe IgA deficiency can form IgE antibodies directed against IgA (anti-IgA antibodies). When transfused with blood products (eg, red blood cells, platelets, fresh frozen plasma) containing small amounts of IgA, these patients can develop potentially fatal anaphylaxis. Therefore, patients with severe IgA deficiency should wear medical alert bracelets and receive blood products that are washed of residual plasma or from an IgA-deficient donor. (Choice A) Bacterial contamination results from bacteria entering the blood component during processing. When these bacteria are introduced during the transfusion, they can cause septic shock (fever, chills, hypotension) but do not cause anaphylaxis. (Choice B) Blood group (eg, ABO, Rh, minor antigen) incompatibility, which is less common with donor O-negative blood, causes an acute hemolytic reaction. Common findings are fever, flank pain, and hemoglobinuria, but not anaphylaxis. (Choice C) Cystic fibrosis (CF) is characterized by abnormal sodium and chloride transport leading to pancreatic insufficiency and chronic, severe respiratory disease. Abnormal antibody production and transfusion reactions are not associated with CF. (Choices D and G) Patients with hyper-IgM syndrome (high IgM; low IgA, IgG) and X-linked (Bruton) agammaglobulinemia (low IgA, IgG, IgM) can also present with recurrent sinopulmonary infections in childhood. However, they do not develop anti-IgA antibodies and therefore do not experience anaphylaxis during transfusions. (Choice F) Wiskott-Aldrich syndrome classically presents in infancy with recurrent sinopulmonary infections, eczema, and thrombocytopenia. It is not associated with anaphylaxis during transfusions. In addition, this patient's platelet count is normal. Educational objective: Selective IgA deficiency is the most common primary immune deficiency, and can present with recurrent sinopulmonary and gastrointestinal infections as well as atopic and autoimmune disease. With severe deficiency, production of anti-IgA antibodies can lead to anaphylaxis during blood transfusion. References: Selective IgA deficiency. (http://www.ncbi.nlm.nih.gov/pubmed/20101521)

An 18-Year-Old Woman Is Brought to the Emergency Department with Severe