Recurrent Neisseria infections are predisposed ina) Early complement component deficiencyb) Late complement component deficiencyc) C1 esterase deficiencyd) Properdin deficiency

## **Core Concept**
The question tests the understanding of the relationship between complement system deficiencies and susceptibility to infections, particularly with Neisseria species. The complement system is a part of the innate immune system that helps eliminate pathogens from an organism. It consists of multiple small proteins found in the blood plasma and on cell surfaces, which cooperate to assist in killing pathogens.

## **Why the Correct Answer is Right**
Late complement component deficiency (options b) is associated with recurrent Neisseria infections. This is because the late components of the complement system (C5-C9) are crucial for forming the membrane attack complex (MAC), which creates pores in the bacterial cell wall, leading to bacterial lysis. Deficiencies in these components impair the ability to effectively clear Neisseria infections, such as Neisseria meningitidis and Neisseria gonorrhoeae.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Early complement component deficiency is more commonly associated with autoimmune diseases, such as systemic lupus erythematosus (SLE), rather than recurrent infections with Neisseria.
- **Option C:** C1 esterase deficiency leads to hereditary angioedema, characterized by recurrent episodes of severe swelling, but it is not primarily associated with recurrent Neisseria infections.
- **Option D:** Properdin deficiency does predispose to recurrent Neisseria infections, particularly Neisseria meningitidis. However, it is less common than late complement component deficiencies and is associated with an increased susceptibility to encapsulated bacteria.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that patients with late complement component deficiencies (C5-C9) are at increased risk of recurrent Neisseria infections. This association is critical for guiding preventive measures, such as vaccination against Neisseria meningitidis.

## **Correct Answer:** B. Late complement component deficiency