Low C4 and normal C3 etiologies
Question:
9/26/2017
34 year-old man with psych hx and seasonal AR c/o swelling since 2/2017 on buttocks, feet, hands, tongue, uvula. No GI sx, arthralgias, fever or rash. Occurs every few days -last 1-48 hrs. Worse with exertion, contact. C4 = 10.8 and 11.6(both dec), C3, ANA, SPEP, C1 est serum and fn, C1q all normal. I think this is idiopathic angioedema but any explanation for low C4 in light of other values being normal?
Answer:
The low C4 and normal C3 would suggest additional diagnoses of SLE, mixed cryoglobulinemia, and membranoproliferative glomerulonephritis. If the cryoglobulins are positive, then could consider hepatitis B and C.
Patricia McNally, MD, FAAAAI