SNP Shot: Genomic Insights

Familial dilated cardiomyopathy (DCM) is a genetic heart condition where the heart muscle, specifically in one or more chambers, becomes thin and weak. This causes the affected chamber to enlarge, a process known as dilation. The heart's ability to effectively pump blood is then compromised. To compensate for this inefficiency, the heart works harder, attempting to pump more blood. Unfortunately, this only exacerbates the thinning and weakening of the heart muscle, ultimately leading to heart failure.

Symptoms of familial DCM often take years to manifest and typically emerge in mid-adulthood, although they can appear at any age. Common signs and symptoms include irregular heartbeats (arrhythmias), shortness of breath (dyspnea), extreme fatigue, fainting spells (syncope), and swelling in the legs and feet. In some instances, the first indication of the disease is sudden cardiac death. The severity of DCM can vary considerably between individuals, even within the same family.

Inheritance:

The inheritance pattern of familial DCM varies depending on the specific gene involved. In the majority of cases (80-90%), it follows an autosomal dominant inheritance pattern. This means that inheriting just one copy of the mutated gene from either parent is enough to cause the condition. While many affected individuals inherit the mutation from a parent who also has the condition, some individuals with the mutated gene may never develop the symptoms of familial DCM, a phenomenon known as reduced penetrance. Furthermore, some cases arise from new gene mutations, occurring in individuals with no family history of the disease.

Less frequently, familial DCM is inherited in an autosomal recessive manner. This requires inheriting two copies of the mutated gene, one from each parent. In this scenario, the parents are carriers of the mutated gene but usually do not exhibit any signs or symptoms of the condition themselves.

In rare instances, familial DCM is inherited through an X-linked pattern. The responsible gene is located on the X chromosome, one of the sex chromosomes. Females, possessing two X chromosomes, have a higher risk of developing the disease if one copy of the gene is mutated, but they may not always develop DCM. Males, with only one X chromosome, will develop familial DCM if their single copy of the gene is mutated. A defining characteristic of X-linked inheritance is that fathers cannot transmit X-linked traits to their sons.