[CIS-PAGID] 16 year old with recurrent pneumonias and low CH50

[M CLAYTON]

I would like to present a young man to the group for advice.  He is a 16 year old Native American boy who lives at Santo Domingo Pueblo near Santa Fe here in New Mexico. He was reportedly in good health (except for recurrent otitis media as a toddler) until 18 months ago when he presented with pneumonia and empyema.  He was hospitalized at a private hospital, and labs at that time showed a CH50 of "0", and quantitative immunoglobulins were reportedly normal.  Other labs included: 
 
AH50=0
Factor D=71 (127-306)
Factor B=92 (123-426)
Properidin=29.4 (22.3-67.6)
C3 fuction WNL (18,317 U/ml)
C4 function decreased =2  (nl range 40000-4300000 U/ml)
 
I was not involved in his care at that point, but he was referred and lost to followup for nearly 12 months.   He reappeared and was again hospitalized with pneumonia.  
A blood culture on admission grew a Beta hemolytic Group B Strep.  The following labs were obtained:    
 
CH50=4
AH50=130
C1 function= 50715 (75672-190932)
C2=0.4 (1.0-4.0), repeated 10 days later= WNL (2.8) 
C3=51 (62-125)
C4=2.5 (15-39)
C6 function=12.0 (32-57)
C7 function=35 (36-60)
ANA screen Negative
Rheumatoid Factor=45 (<15 IU/ml)
Diptheria IgG=.74
Tetanus IgG=.42
8/12 pneumococcal IgG titers > 1.0 ug/ml
 
Approximately 10 days after above labs:
C3A, C4A, C5A all WNL
 
IgG, A, M, E all WNL.  Immune Deficiency panel WNL.

What conclusions can I draw from these labs?  Several components were low during the most recent hospitalization suggesting consumption, but the very low C4 function during his initial illness and the persisting low C4 level made me wonder about a C4 deficiency.  Could it be a mixed process?  Any comments or suggestions would be welcome.  
Thanks in advance, and Happy Holidays to all-
 
 
Michael H. Clayton, MD, MPH
Assistant Clinical Professor
UNM Dept. of Pediatrics   		 	   		  
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