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

[dmvascon at usp.br]

Dear Ashish

I would suggest to test for APH50, in order to evaluate alternate  
pathway function. The combination of both functional screening tests  
(CH50 and APH50) is very useful to drive the evaluation of complement  
defects:

CH50 indetectable, APH50 normal: defects of classical pathway activation
CH50 normal, APH50 indetectable: defects of alternate pathway activation
CH50 and APH50 indetectable: defects of membrane attack complex.

These functional tests are fundamental, due to the fact that in a  
qualitative defect of any component of complement (without  
quantitative defect), there will be a reduction of the value of the  
screening test, without reduction of the quantitation of any component  
by any immunochemical method (nephelometry, turbidimetry etc.).

Usually complement deficiencies present clinical manifestations later  
in life (usually autoimmunity in classical pathway activation  
components - C1, C4, C2) and infections by encapsulated bacteria -  
mainly Neisserial infections - with alternate pathway or membrane  
attack complex component deficiencies.

Therefore it is important to test for other possible complement  
defects and follow-up these patients closely to detect any possible  
clinical and immunological manifestation as early as possible.

Best regards,

Dewton


Citando Ashish Kumar <Ashish.Kumar at cchmc.org>:


> 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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