[Human creatine kinase deficiency].
We describe a 56-year-old woman hospitalized under a diagnosis of acute myocardial infarction without an increase in serum creatine kinase(CK) activity during the clinical course. The patient had had no previous muscular symptoms. CK-M protein in the myocardial tissue of the patient was substantially lower(103 +/- 7 ng/mg protein) than that in control myocardial tissue(35,800 +/- 2860 ng/mg protein). Immunoreactive CK-M in the patient tissue sample was 0.3% of the value for the control sample. CK-M mRNA was 53-fold less in the patient sample compared with the control. This very low expression of CK-M mRNA was considered to be the primary reason for CK-M deficiency. Direct sequencing demonstrated a point mutation at residue 54 in exon2, which was specific for the patient. There were no other abnormalities found in the CK-M gene of the patient. This report identifies a molecular abnormality in human CK deficiency and discusses the physiologic relevance of CK-M.