Low C1q and swelling in a patient with history of multiple myeloma
Question:
11/8/2019
I have 83 year-old male with poorly described swelling which I was initially concerned about acquired angioedema since he has history of multiple myeloma. His lab work showed C1q <3.6 (range 5-8.6), C1 esterase inhibitor 40 (range 21-39) with C1 esterase function 100 %, C3 141 (range not established for age >81, normal range 82-185 from age 15-80), C4 46 (normal range 15-53 for age 15-80). Could his low C1q be due to his history of multiple myeloma or do I need to work him for something else?
Answer:
I am curious about the "poorly described swelling." It would be helpful to have the patient provide documentation, such as a photograph, in order to ascertain if it is angioedema or not. Also, the C1q is only slightly below the lower limit of normal. I would consider repeating the C1q. One would expect that the C4 would also be low if this were acquired angioedema.
The causes of low C1q in the face of normal parameters as you mention would include hypocomplementemic urticarial vasculitis (HUVS), so it would be helpful to determine if the swelling is urticarial or not; SLE (though one would expect low C4), congenital (which is very rare but associated with glomerulonephritis and pyogenic infections).
Does the patient have a low albumin? You might consider urinalysis to check for protein loss. You might also speak with the patient's oncologist about the current status of the multiple myeloma.
I hope this is helpful to you and your patient.
Jacqueline A. Pongracic, MD, FAAAAI