​Frequently Asked Questions

  • 1p36 deletion syndrome is most commonly diagnosed by chromosomal microarray analysis (CMA). This test can determine both the size and location of the DNA missing on chromosome 1p36. Occasionally, a 1p36 deletion may be identified using high-resolution chromosome analysis or a test called fluorescent in-situ hybridization (FISH). If a diagnosis of 1p36 deletion syndrome is made using one of these techniques, it may be helpful to further define the deletion using CMA.

    Many children are now being tested for genetic disorders using whole exome sequencing (WES) and whole genome sequencing (WGS). Although these tests are designed to look for small changes in the letter-code of the DNA, software tools have been developed which allow them to also detect deletions. If a 1p36 deletion is detected using one of these methods, no additional testing is required unless a geneticist feels that there is a need to confirm the presence of the deletion.

  • 1p36 deletion syndrome is caused by a missing piece (deletion) of chromosome material from a region on the top of the short arm of chromosome 1. Most people have 46 chromosomes. Chromosomes are arranged in pairs, with one copy coming from the mother and the other from the father. Chromosomes contain the genetic material that our bodies need to grow and develop. People with 1p36 deletion syndrome are missing some of the genetic material needed for normal development. Although we do not know exactly why chromosome deletions occur, there is no evidence that parents could have done anything to cause or prevent 1p36 deletion syndrome.

  • No, unfortunately it is not possible to replace missing chromosome pieces. However, treatments are available for many of the problems associated with this condition.

  • Making a diagnosis of 1p36 deletion syndrome is important in several ways. Knowing your child has 1p36 deletion syndrome allows you and your child's physicians to plan for the child's specific medical needs. A diagnosis can also help physicians recognize and treat problems early. A specific diagnosis allows for educational planning with special emphasis on speech and language problems and other issues common to 1p36 deletion syndrome. Making this diagnosis also allows for accurate genetic counseling and the option of prenatal testing in future pregnancies. Just as important, is the ability of parents and caregivers to join the 1p36 deletion syndrome community to be able to learn and share with those who also have loved ones with 1p36 deletion syndrome.

  • A team of doctors and medical specialists is needed to care for many children with 1p36 deletion syndrome. In addition to the child's pediatrician, members of this team may include a medical geneticist; cardiologist; neurologist; ophthalmologist; nutritionist; and physical, occupational and speech therapists. Other specialists may also be needed depending on the child's specific needs.

  • Because 1p36 deletions can vary int their extent and loction, there are no standardized health care guidelines available. Recommendations, however, may include the following:

    • An echocardiogram (ultrasound) of the heart to determine if there is a heart defect or cardiomyopathy

    • An eye exam to determine if there are any vision or eye problems

    • A complete hearing test (including high frequencies) to detect hearing problems, many times for young children this is in the form of an ABR (Auditory Brainstem Response) test

    • A CT scan or MRI of the brain to rule our brain malformations

    • Evaluation of feeding and growth as a newborn, and at regular intervals during childhood

    • Developmental assessments with speech, physical and occupational therapists

    • Blood tests for thyroid dysfunction at birth and six months of age, and then annually

  • Most 1p36 deletions are de novo, meaning that they are not inherited from a mother of father whose chromosomes are normal. In this case, the chance that a future child or grandchild will have a 1p36 deletion syndrome is low (1-2%). Occasionally, a parent may have a chromosome rearrangement that significantly increases the chances of having another child or grandchild with 1p36 deletion syndrome. To distinguish between these possibilities, it is recommended that all parents of children with 1p36 deletion syndrome should have genetic counseling and undergo chromosome analysis and/or FISH testing depending on the size of the deletion. A chromosomal microarray analysis (CMA) should not be used to test parents for a chromosomal rearrangement since it will not pick up "balanced" rearrangements in the parents in which genetic material has been moved from one chromosome region to another. If a parent carries a balanced chromosomal rearrangement, the chance that a future child or grandchild might have 1p36 deletion syndrome may be increased.

    If you have questions regarding future pregnancies, we recommend contacting a genetics provider. Genetic counselors are health professionals with specialized training and experience in medical genetics and counseling. Clinical geneticists are physicians who diagnose, treat, and counsel patients and families with genetic conditions. Both geneticists and genetic counselors can talk with you about your family history and the implications for future pregnancies.

  • It is estimated that 1p36 deletion syndrome affects one in every 5,000 to 10,000 newborns, though many individuals still go undiagnosed. Deletions of chromosome 1p36 are the most common terminal deletions in humans.

  • Each chromosome arm is divided into arms, and regions, bands, subbands, and subsubbands that can be seen using a microscope with special stains. Each chromosome has two arms that extend from the centromere, an area of special repetitive DNA located between each arm. The shorter arm of the chromosome is described as the “p” arm, and the long arm is described as the “q” arm. The are labeled p1, p2, p3, q1, q2, q3, etc., counting from the centromere out toward the telomeres (the ends). The bands, subbands and subsubbands are also numbered starting at the centromere.

    If an individual has a 1p36.33p36.32 deletion, it means that the ends of their deletion are within chromosome 1, short arm, region 3, band 6, subband 3, subsubbands 3 and 2. These type of descriptions are imprecise and only provide an approximation of the location and extent of the deletion.

    When a 1p36 deletion is detected using a chromosomal microarray analysis (CMA), whole exome sequencing (WES), or whole genome sequencing (WGS), the genetic report will provide a more detailed description of the deletion using numbers. Each letter of DNA is numbered starting at the telomere of the short arm and ending at the telomere of the long arm. In this case, the test showed that the deletion spans a region between letter 825,513 to letter 2,568,383. This region can also be described as chr1: 825,513-2,568,383.

    In some cases, the deletion may be larger than what is described by the numbers but can’t be defined further due to the limitations of the test. This often is the case when the deletion involves the telomere of chromosome 1p which is make up of repetitive DNA. In such cases, the test may say that the deletion is “telomeric”, meaning that it likely starts at the tip of the chromosome (chr1:1-2,568,383) even though the test can’t prove that the telomere has been deleted. This is in contrast to an “interstitial deletion” which does not involve the telomere.

    Most individuals have two copies of chromosomes 1p36, or x2. A deletion would be labeled as x1 since it leaves an individual with only one copy of the DNA at that location. A triplication would be labeled as x3.

  • A chromosome, and therefore the genes that are on the chromosome, is made of a chemical called deoxyribonucleic acid, or DNA. DNA is composed of four chemical components called bases. The four bases are adenine, thymine, cytosine, and guanine. These components are symbolized by using one of 4 letters (A, T, C, or G).

    DNA is made of two strands, each composed of a long string of the A’s, T’s, C’s, and G’s. The two strands run parallel to one another. In fact, the structure of DNA is often described as a twisted ladder. To create the ladder’s rungs, each of the bases on one strand is paired to a base on the other strand. Chromosome 1 is the largest human chromosome, spanning about 249 million base pairs (249 Mb) and representing approximately 8 percent of the total DNA in cells.

    So, if a deletion is 2.5 Mb in size it deletes 2,500,000 base pairs.  Knowing the size tells us how big the deletion is, but not where it begins and ends.  The exact location of a deletion can be represented by providing the numbers of the base pairs where the deletion begins and ends. For example, a chr1:1,000,000-3,500,000 deletion begins 1 million base pairs from the top of chromosome 1, extends for 2.5 million base pairs (2.5 Mb), and ends 3.5 million base pairs form the top of chromosome 1.

  • In general, the size of a 1p36 deletion alone can’t be used to accurately predict the type and severity of symptoms a child will have. However, we are learning more about the role of each gene on chromosome 1p36. This can help us to know what types of medical problems a child MIGHT develop based on the location and extent of their deletion. For example, deleting the PRDM16 gene brings with it an increased risk of developing cardiac muscle problems (cardiomyopathy). Other genes play important roles in brain development and function. Deleting these genes brings an increased risk of having developmental delay, intellectual disability, and/or seizures.

    Although larger deletions typically affect more genes, a child with a smaller deletion may have fewer or less severe symptoms than a child with a larger deletion. We also know that children with the exact same 1p36 deletion may have different medical problems. These differences may be due to positive or negative changes in other genes, differences in their environment, or other factors that are hard to predict.