In cases of acquired angioedema, which complement component is noted to be decreased?

In cases of acquired angioedema, the decrease in complement component C1q is significant because it plays a crucial role in the complement system's function and regulation. Acquired angioedema often occurs due to conditions of complement system dysfunction, frequently related to the presence of C1 inhibitor deficiency or dysfunction.

In this context, measuring complement levels can help differentiate between hereditary and acquired forms of angioedema. In acquired angioedema, particularly associated with lymphoproliferative disorders or the use of ACE inhibitors, there is typically a decrease in C1q and C4 levels due to consumption. However, C1q is more specifically mentioned in the context of acquired angioedema as it is involved in the recognition of pathogens and mediating the clearance of immune complexes.

Understanding the roles of different complement components helps in determining the underlying pathophysiology of angioedema and guiding appropriate treatment strategies. Thus, the noted decrease in C1q in cases of acquired angioedema is a key indicator in clinical evaluations.