IgA-CK-BB complex with CK-MB electrophoretic mobility can lead to erroneous diagnosis of acute myocardial infarction.
This patient, on admission, presented with a tentative diagnosis of myocardial infarction: the electrocardiogram showed a nonspecific ST-segment and T-wave abnormalities, and total creatine kinase (CK; EC 2.7.3.2) activity was slightly increased (238 U/L). However, a high electrophoretic value for CK-MB (50% of total CK activity) and the electrophoretic pattern of lactate dehydrogenase (EC 1.1.1.27) isoenzymes ruled out myocardial infarction. The isoenzyme migrating as CK-MB was found later to contain no immunologically normal CK-M subunits, and it was bound to IgA. A mixture of the patient's serum and a human serum control containing all CK isoenzymes showed altered electrophoretic mobility only for CK-BB, indicating that the patient's serum contained antibodies to the B unit of CK. Elution from a Sephadex G-200 column showed that the peak at which most of the anodic CK was eluted corresponded to a molecular mass of approximately 200 kDa. Evidently this atypical isoenzyme was an IgA-CK-BB complex. Because this macro CK type 1 can mimic CK-MB, it may therefore be a source of confusion.
Servicio de Análisis Clínicos, Hospital San Agustin, Avilés, Asturias, Spain.
R
R
Venta
S A
SA
Geijo
A C
AC
Sánchez
C G
CG
Bao
L A
LA
Bartolome
G
G
Casares
C
C
Lopez-Otin
F V
FV
Alvarez
D003402:Creatine Kinase / Q000097:blood* / Q000276:immunology; D003951:Diagnostic Errors; D004586:Electrophoresis / Q000379:methods; D006801:Humans; D007070:Immunoglobulin A / Q000032:analysis*; D007527:Isoenzymes; D007770:L-Lactate Dehydrogenase / Q000097:blood; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis / Q000201:enzymology*; D013050:Spectrometry, Fluorescence
D007070:Immunoglobulin A; D007527:Isoenzymes; D007770:L-Lactate Dehydrogenase; D003402:Creatine Kinase