Hypertrophic cardiomyopathy (HCM) is a myocardial disease with variable 
phenotpye and genotype. To demonstrate that the mutation Arg719Trp in the 
cardiac beta-myosin heavy chain (beta MHC) gene is a high risk factor for sudden 
death and can be associated with an unusual apical non-obstructive HCM, we 
report the case of a 6 1/2 year old boy, who suffered cardiac arrest. The 
proband had a de novo mutation of the beta MHC gene (Arg719Trp) on the paternal 
beta MHC allele and a second maternally transmitted mutation (Met349Thr), as was 
shown previously (Jeschke et al. 1998 (11)). Here we report the clinical 
phenotype of the proband and of his relatives in detail. The proband had a 
marked apical and midventricular hypertrophy of the left and right ventricle 
without obstruction. There was an abnormal relaxation of both ventricles. Holter 
monitoring detected no arrhythmia. Ventricular fibrillation was inducible only 
by aggressive programmed stimulation. The boy died 3 1/2 years later after 
another cardiac arrest due to arrhythmia. Five carriers of the Met349Thr 
mutation in the family were asymptomatic and had no echocardiographic changes in 
the heart, suggesting a neutral inherited polymorphism or a recessive mutation. 
It is concluded that there is an association of the mutation Arg719Trp in the 
beta-myosin heavy chain with sudden cardiac death in a young child. Disease 
history in conjunction with the genetic analysis suggests that the implantation 
of a defibrillator converter would have been a beneficial and probably life 
saving measure.