Are all genetic disorders inherited from parents?

Not necessarily. While many genetic disorders are passed down through generations, other types arise as a result of genetic changes that occur during an individual's lifetime and are not inherited from parents [1].

What are genetic disorders?

Genetic disorders are health conditions caused by changes (also known as mutations or variants) in genes. Genes are segments of DNA found in the body's cells that carry instructions for how the body grows, develops, and functions. When these instructions are altered, it may lead to a malfunction in the production of proteins necessary for the body to function correctly, causing disease [1]. For example, sickle cell anemia is a genetic disorder that occurs due to a change in a single gene [1].

Types of genetic changes

Genetic changes can be classified into two main types:

• Germline variants: These variants are passed from parents to children via reproductive cells (eggs or sperm). If one parent carries a variant gene, it may be passed on to the child, increasing the risk of developing a genetic disorder [1]. For example, Infantile Neuroaxonal Dystrophy (INAD) is an autosomal recessive genetic disorder that occurs when a child inherits a variant gene from both parents [2].
• Somatic variants: These variants are not passed on from parents. They occur during an individual's lifetime and may be caused by environmental factors such as harmful chemicals or ultraviolet (UV) radiation from the sun [1]. These changes only affect the cells in which they occur and are not passed on to future generations.

Inheritance patterns

Some genetic conditions are passed through families in different patterns, depending on the specific gene involved. Inheritance patterns can include:

• Dominant inheritance: The presence of just one variant gene is sufficient to cause the condition [1].
• Recessive inheritance: This requires the presence of two variant copies of the gene (one from each parent) for the condition to occur [1].
• X-linked inheritance: This involves genes located on the X chromosome and often affects males more frequently [1].
• Mitochondrial inheritance: These conditions are passed down from the mother [1].

The importance of genetic counseling

If there is a family history of genetic disorders, or if there is concern about passing a genetic disease to children, genetic counseling can be extremely beneficial. A genetic counselor can evaluate the family's medical history, explain potential inheritance patterns, and discuss available genetic testing options [1]. For example, in the case of a child with Infantile Neuroaxonal Dystrophy (INAD), siblings have a 25% chance of developing the same disease, and genetic counseling can help families understand these probabilities [2]. To learn more about this topic, you can visit Common Genetic Disorders: A Comprehensive Guide for Understanding and Living (Arabic).

Medical references

• Genetic Disorders
• Infantile Neuroaxonal Dystrophy