Question

A patient with recurrent Neisseria infections is evaluated for complement deficiency. C3, C4, and C5 levels are all within normal limits. CH50 values are below the reference range. What could explain these results?

A. Patient has a deficiency of C1

B. Patient has non-functioning C4

C. Patient has non-functioning C5

D. Patient has a deficiency of Factor D

Answer 1

The answer is option A - the patient has a deficiency of C1.
Explanation -The complement cascade system is a part of our innate immune system where special proteins in blood stream are responsible for enhancing the abilities of antibodies to fight against antigens by marking pathogens or by destroying them by phagocytes and also clear damaged cells, induce inflammatory responses to help fight infection.
Complement test is a blood test that measure the activity of these group of proteins by which doctors can diagnose certain auto immune disease and other disease related to immune deficiencies.
There are 9 most important complements C1 to C9 that regulates the whole functions.
Patients with complement deficiencies faces frequent recurrent infections and mortality to a higher extent. They mainly lack C3, the major opsonin or a D-FACTOR that results these recurrent infections particularly with encapsulated bacteria.
The CH50 test or a total hemolytic complement measurement is one of most common tests to find out deficiencies of complement pathway. Test that result specific complement protein measurement can also done.
Both the low and high level of these proteins indicates problems.
A LOW LEVEL OF CH50 SUGGEST DEFICIENCY OF ONE OF THE COMPLEMENT PROTEINS OF THE PATHWAY ( C1- C9), here in the question, c3, c4, c5 are measured separately with normal values that left only c1 that can cause the low value of ch50 test.