Background: Deletion of lysine 183 (K183del) in the cardiac troponin I (cTnI) gene is one of the mutations that causes hypertrophic cardiomyopathy (HCM). However, the phenotypic expression of this mutation has not been well established.
Methods and results: We analyzed 10 probands with HCM associated with a K183del in the cTnI gene, as well as their family members. Forty-seven of these 80 subjects were found to be carriers and 33 were noncarriers. In the carrier subjects, electrocardiogram (ECG) abnormalities were initially noted during the early teenage years preceding echocardiographic abnormalities. Abnormal Q waves were found first and most frequently compared with other ECG abnormalities. Abnormal Q waves were frequently observed in leads II, III, aVF, V5, and V6 in teenage patients, whereas they were observed in many leads in patients >20 years old. The youngest of the 11 patients who had sudden cardiac death among studied pedigrees was a 14-year-old boy.
Conclusions: These results suggest that the first phenotypic manifestation in patients with HCM associated with a K183del mutation in the cTnI gene is abnormal Q waves in leads II, III, aVF, V5, and V6 during the early teenage years. To prevent sudden death in family members of patients with this mutation, it may be necessary to genetically diagnose it before age 10 years and to pay careful attention to any development of abnormal Q waves.