Differential Diagnosis
- Single most likely diagnosis
- D) Selective IgA deficiency: This is the most likely cause of the frequent infections, given the patient's history of anaphylactic reaction to a blood transfusion. Selective IgA deficiency is the most common primary immunodeficiency and can lead to increased susceptibility to infections, particularly of the respiratory tract. The anaphylactic reaction to blood transfusion is a classic presentation, as individuals with selective IgA deficiency may develop anti-IgA antibodies, which can cause a severe reaction when exposed to IgA in transfused blood products.
- Other Likely diagnoses
- B) Common variable immunodeficiency: This condition is characterized by impaired antibody production, leading to recurrent infections. While the patient's serum protein electrophoresis is within normal limits, common variable immunodeficiency can have a variable presentation, and some patients may have normal immunoglobulin levels.
- C) HIV infection: Although the patient is asymptomatic, HIV infection can cause recurrent infections, particularly of the respiratory tract. However, the patient's age, lack of other symptoms, and normal complete blood count make this diagnosis less likely.
- Do Not Miss
- E) X-linked agammaglobulinemia: Although rare, this condition is a "do not miss" diagnosis, as it can lead to severe and life-threatening infections. X-linked agammaglobulinemia is characterized by the absence of B cells and impaired antibody production, leading to recurrent infections from an early age.
- Rare diagnoses
- A) Colonization with Streptococcus pneumoniae: While colonization with Streptococcus pneumoniae can lead to recurrent infections, it is not a primary immunodeficiency and would not explain the patient's anaphylactic reaction to a blood transfusion. This diagnosis is less likely and would require further investigation to confirm.