[Human creatine kinase deficiency].

Area of Science:

• Biochemistry
• Molecular Biology
• Cardiology

Background:

• Creatine kinase (CK) is a crucial enzyme for cellular energy homeostasis, particularly in high-energy-demand tissues like the heart.
• Serum CK levels are a standard biomarker for diagnosing myocardial infarction (MI).
• CK-M is the predominant CK isoenzyme found in myocardial tissue.

Observation:

• A 56-year-old female patient presented with acute myocardial infarction but showed no significant increase in serum CK activity.
• Myocardial tissue analysis revealed a severe deficiency in CK-M protein (0.3% of control levels).
• CK-M messenger RNA (mRNA) levels were significantly reduced (53-fold less than controls) in the patient's heart tissue.

Findings:

• A specific point mutation in exon 2 of the CK-M gene was identified as the cause of the deficiency.
• This mutation appears to be the sole genetic abnormality affecting CK-M in this patient.
• The reduced CK-M mRNA expression directly correlates with the observed protein deficiency.

Implications:

• This case highlights a novel molecular basis for CK deficiency, distinct from previously known causes.
• It underscores the importance of CK-M in myocardial energy metabolism and its role beyond being a simple biomarker.
• Understanding such genetic variations is crucial for accurate diagnosis and comprehending the physiological impact of enzyme deficiencies.