What are Chromosomes and Genes?

Chromosomes are like instruction manuals for our bodies. They carry all the information that makes us who we are—how we look, how our bodies grow, and function. Each person has 46 chromosomes, which are grouped into 23 pairs. One set of these pairs comes from the individual’s mother, and the other set comes from the father. Each chromosome is made up of genes, which are like tiny instructions that tell our bodies how to work.

Think of chromosomes as books on a bookshelf. Each of these books contains many pages, and those pages are like genes. The pages (genes) hold the specific instructions for how our bodies grow, develop, and function. We have 46 of these “books” in our cells, grouped into 23 pairs. Just as every book needs its pages in the right order to make sense, chromosomes need their genes to be arranged correctly for our bodies to function properly. Sometimes, however, a chromosome (book) might have extra pages, missing pages, upside-down pages, or pages out of order. When this happens, it can change the “instructions” that tell our body how to operate.

When someone has a chromosome change, like a rearrangement on chromosome 8p, it can affect their growth, development, and health. Researchers and physicians are still learning how these changes impact each person, but we do know that rearrangements on chromosome 8p affect every cell in the body.

Chromosome 8p Rearrangements:

Each cell contains two copies of Chromosome 8—one inherited from the mother and one from the father. In individuals with a chromosome 8p rearrangement, one of these copies is normal, while the other has a change, such as a duplication, deletion, or other rearrangement on the short arm (p arm).

Compare the unaffected Chromosome 8 on the left to the affected chromosomes on the right:

Proteins are made from both of the chromosomes in each pair. When part of the chromosome is deleted, fewer proteins are produced from that region. Conversely, a duplication leads to more proteins being made. However, the relationship between these changes and protein production isn’t always straightforward, as cells can react in unique ways to changes in DNA.

How is a Chromosome 8p Rearrangement Diagnosed?

Chromosome 8p rearrangements can be diagnosed through various genetic blood tests. The most common methods include:

• Whole Exome Sequencing (WES) or Whole Genome Sequencing (WGS): These advanced tests provide detailed information about the genetic makeup, identifying changes within the genes themselves. (Recommended)
• Microarray Analysis: This test detects small changes in chromosomes, such as duplications, deletions, translocations, and/or inversions.
• Chromosome Analysis (Karyotype): This technique looks at the size, shape, and number of chromosomes to identify any rearrangements in chromosomes.
• Fluorescence In Situ Hybridization (FISH): This method can detect specific chromosome changes.

Prevalence

Determining the exact number of individuals affected by chromosome 8p rearrangements is challenging. However, it is estimated that this rare genetic condition impacts approximately 550 people worldwide, with numbers continuing to grow as awareness and diagnostic methods improve.

Is 8p Hereditary?

In most cases, chromosome 8p rearrangements appear to result from spontaneous (de novo) errors that occur early in embryonic development. These changes arise for unknown reasons and are typically not inherited. However, recent findings have identified families where the chromosome 8p rearrangement is inherited, with varying manifestations of symptoms among family members.

If a chromosome 8p rearrangement has been confirmed, the parents’ chromosomes can be tested to determine whether the change is inherited or de novo. It’s important for parents to know that there is nothing they did to cause this rearrangement, nor anything they could have done to prevent it. Chromosome rearrangements can occur in families of all backgrounds. In de novo cases, these changes are typically the result of an accidental error during the formation of egg or sperm cells, and the chances of having another child with the same condition are usually not higher than for anyone else in the population.

Genetics Appointments:

Consulting with a clinical geneticist or genetic counselor is crucial to help families understand the diagnosis and its potential impacts.

Families may wish to pursue genetic testing to make an informed decision in regards to family planning. A clinical geneticist can guide families through this process, providing support and assistance with the decision-making and testing.

Additional Genetic Testing:

If the clinical presentation does not align with the current molecular diagnosis or if previous genetic analysis was done with a resolution lower than a 180kb oligoarray, it may be necessary to update genetic testing.