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Congenital Athymia - Video

The animated videos in NORD’s Rare Disease Video Library provide brief introductions to rare disease topics for patients, caregivers, students, professionals and the public. NORD collaborates with medical experts, patient organizations, videographers and Osmosis to develop the videos, which are made possible by individual donations, educational grants and corporate sponsorships. NORD is solely responsible for the content.


General Discussion

Summary

Congenital athymia is a rare disorder in which children have no detectable thymus (athymia). The thymus is a gland located on top of the heart. The thymus produces specialized white blood cells called T cells that fight infections, especially viral infections. The T cell count is the highest in infants in the first 2 years of life and then slowly decreases with time. In adults over the age of 60, the thymus is mostly replaced by fat. Children with congenital athymia are born without a thymus and are therefore profoundly deficient in T cells and extremely susceptible to infections. Without treatment, the disorder is usually fatal by two to three years of age.

Introduction

The following conditions can result in congenital athymia:

• complete DiGeorge syndrome, also known as complete DiGeorge anomaly
• 22q11.2 deletion syndrome
• CHARGE syndrome
• infant of diabetic mother
FOXN1 gene deficiency
TBX1 gene mutation
TBX2 gene mutation
PAX1 gene deficiency
SEMA3E gene mutation

Most infants with congenital athymia have chromosome 22q11.2 deletion syndrome or CHARGE syndrome. Both disorders have symptoms affecting multiple systems of the body. These infants have a set of T cells called “naïve T cells” or “recent thymus emigrants” that are less than the 100/mm3. These T cells are critical for the health of the infant. These infants will die unless placed in permanent complete isolation.

In the past, children with T cells below the 10th percentile for age were said to have DiGeorge syndrome (named after a medical student who first reported the condition). However, most of these patients did well. Only about 1% of children with DiGeorge syndrome have lower than 100 naïve T cells/mm3. This group of patients is the group with congenital athymia. NORD has individual reports on 22q11.2 deletion syndrome and CHARGE syndrome and these reports are accessible on the NORD website in the Rare Disease Database.


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