[CIS-PAGID] low ch50 with normal complement levels?

[Ashish Kumar]

Dear Friends,
 
I recently saw a set of twin girls who were born at 32 weeks with twin-twin transfusion syndrome; the smaller of the two has needed a couple hospitalizations with URIs due to hypoxia. She has chronic rhinorrhea, a history of wheezing that responds to bronchodilator therapy. Someone checked her ch50 and it was <10; recheck showed the same. Her twin was then checked and hers too was <10. Their complement levels are all normal, except I don't have results on C2. They are 18 months old, have normal immune globulins, lymphocyte numbers and no serious infections. The smaller twin hasn't needed hospitalization since March, even though she has had a couple URIs since then - probably because of the season, growth and better asthma control. So, they were sent to me for consult because of the low ch50. Since the testing is sensitive to sample handling, I thought to repeat it and it is still low. I cannot reconcile the history of no serious infections with low ch50 but normal complement levels. Is this just a testing aberration? Any suggestions/ideas?
 
Thanks!
Ashish Kumar
 
Ashish Kumar, MD, PhD
Assistant Professor
Cincinnati Children's Hospital Medical Center
Cincinnati, OH
 
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