A patient is diagnosed with selective IgA deficiency, a primary immunodeficiency disorder. Which of the following complications is most commonly associated with this condition?

Correct Answer: A

Rationale: Selective IgA deficiency is a primary immunodeficiency disorder characterized by low or absent levels of immunoglobulin A (IgA) in the blood. Since IgA plays a crucial role in mucosal immunity and defense against pathogens at mucosal surfaces, individuals with this deficiency are more susceptible to recurrent bacterial infections, particularly of the respiratory and gastrointestinal tracts. In contrast, severe combined immunodeficiency (SCID) is a more severe immunodeficiency disorder affecting T and B lymphocytes, chronic granulomatous disease (CGD) is a disorder of phagocytes, and autoimmune hemolytic anemia is an autoimmune disease involving red blood cells, none of which are directly associated with selective IgA deficiency.

Correct Answer: C

Rationale: In a pregnant patient with suspected pulmonary embolism (PE), the most appropriate imaging modality for evaluation is contrast-enhanced computed tomography (CT) pulmonary angiography. This imaging technique has been shown to be safe for the fetus when necessary, especially if the benefits of making a diagnosis outweigh the minimal risks associated with radiation exposure. It provides quick and accurate detection of PE with high sensitivity and specificity.

Correct Answer: A

Rationale: In this case, the patient is experiencing respiratory acidosis as indicated by the low pH (7.28), elevated PaCO2 (65 mmHg), and elevated HCO3- (30 mEq/L). The primary acid-base disturbance is respiratory acidosis due to the retention of carbon dioxide (PaCO2 >45 mmHg) leading to an increase in HCO3- as a compensatory mechanism to maintain pH within normal limits. The elevated HCO3- levels (metabolic compensation) are trying to counterbalance the increased PaCO2 levels (respiratory acidosis) by increasing bicarbonate to attempt to normalize the pH. Overall, the ABG analysis shows respiratory acidosis with metabolic compensation in this COPD patient with an acute exacerbation and severe dyspnea.

Correct Answer: D

Rationale: The clinical presentation of a patient with chronic kidney disease (CKD) presenting with weakness, anorexia, confusion, severe anemia, low reticulocyte count, elevated serum creatinine, and decreased erythropoietin levels is most consistent with renal failure-associated anemia. In CKD, the kidneys are unable to produce adequate amounts of erythropoietin, a hormone responsible for stimulating red blood cell production in the bone marrow. The decreased erythropoietin levels lead to a state of anemia, characterized by low hemoglobin levels and subsequent symptoms of fatigue and weakness. The anemia in renal failure is typically normocytic and normochromic. Additionally, the elevated serum creatinine in this patient is a hallmark of kidney dysfunction.

Correct Answer: B

Rationale: Thrombotic thrombocytopenic purpura (TTP) is a rare blood disorder characterized by microangiopathic hemolytic anemia, thrombocytopenia, fever, neurological abnormalities, and renal dysfunction. The peripheral blood smear in TTP typically shows fragmented red blood cells (schistocytes) due to mechanical destruction within small blood vessels. Laboratory findings in TTP commonly include elevated lactate dehydrogenase (LDH), decreased haptoglobin (as it is consumed in the clearance of free hemoglobin), and increased indirect bilirubin due to increased red blood cell breakdown. This combination of clinical presentation and laboratory abnormalities is classic for TTP. Hemolytic uremic syndrome (HUS) may present similarly but is more commonly associated with renal dysfunction and is often triggered by infection with Shiga toxin-producing E. coli.