The objective of this study is to collect information on patients with cardiomyopathy (CM) due to mutations in the MYBPC3 gene, to evaluate their disease course, burden of illness, risk factors for this disease, and the quality of life (QoL). This study will also collect information on treatments, procedures and outcome in infants and children up to 18 yrs who have this mutation.

Retrospective

Inclusion Criteria:

• Data is available for patient <18 years of age. Patients must be <18 years of age at enrollment or at time of death.
• Documented results of genotyping showing the presence of at least one pathogenic or likely pathogenic MYBPC3 mutation (heterozygous, homozygous, or compound heterozygous).

Exclusion Criteria:

• Patient received cardiac transplantation or died >10 years before study initiation. For homozygous or biallelic infants, data may be collected beyond this 10-year period.

Prospective

Inclusion Criteria:

For Infants:

• Infants who are homozygous or compound heterozygous for the known pathogenic truncating MYBPC3 mutations are eligible.

For all other participants:

• Age <18 at entry into the prospective study.
• Documented results of genotyping identifying at least one pathogenic or likely pathogenic MYBPC3 mutation (heterozygous, homozygous, or compound heterozygous).
• Diagnosis of Cardiomyopathy (CM): HCM, DCM, RCM, mixed CM, or LVNC.

Exclusion Criteria:

• Concurrent participation in an interventional clinical trial unless approved by the sponsor.
• Severe noncardiac disease anticipated to significantly reduce life expectancy.

Patients under the age of 18 years (at enrollment) with cardiomyopathy (CM) and pathogenic or likely pathogenic MYBPC3 genetic mutation