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Mosaic and Non-Mosaic Down Syndrome

Our body is made up of different cell types. However, though they may be different because of their functions, these cells all originated from one single fertilized egg or zygote. It started from a zygote with only one cell, and then it duplicates and divides into two cells. These two cells will continue duplicating and dividing to create more cells and so on. The process of cell duplication and division occurs over the course of a person’s life.

In a normal human cell, it contains 46 chromosomes and paired to form 23 chromosomes. In mosaic trisomy 21, the error occurs after the zygote was formed. This occurred during the early cell division. People with mosaic Down syndrome have two cell lines: one with the normal number of chromosomes, and one with an extra chromosome 21. Individuals with mosaic Down syndrome may have less obvious features of Down syndrome and the resulting problems associated with the disorder will depend on the number of cells present in the person’s body.

Non-Mosaic Down syndrome has full trisomy 21. With full trisomy 21, instead of having two chromosomes, it has three chromosomes on number 21. The extra chromosome 21 resulted from an error in the chromosomes of the egg or sperm cell before becoming a zygote. After this all happened before the fertilization, every cell that duplicates and divides from this zygote will have an extra chromosome 21.

Individuals with non-mosaic Down syndrome have typical facial features, delayed physical development, and general learning disability. Additionally, they may also have congenital heart disease, problems with vision, hearing disorders and other disorders.

Common facial characteristics of people with non-mosaic Down syndrome:

  • Has an oval shaped face
  • Slanting eyes and an extra skin fold on the upper eyelid
  • Small mouth with a tongue that protrudes often
  • Flatter than normal occiput, located in the back of their head
  • Their nose may be small and have a low and flat bridge
  • The ears are low-set and may be small

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If you think you are suffering from Mosaic and Non-Mosaic Down Syndrome you should seek medical assistance. You may also be entitled to Social Security Disability Benefits. The SSA considered Mosaic and Non-Mosaic Down Syndrome as a medical condition that would make you eligible for SSDI and SSI. Social Security Administration (SSA) maintains a “Listing of Medical Impairments” (known as the blue book) that automatically qualify you for Social Security Disability Insurance (SSDI) or Supplemental Security Income (SSI).