Chromosomal Disorders with Immune Deficiency (Pediatric)
What are chromosomal disorders with immune deficiency?
These disorders occur when there are missing, extra, or irregular parts of a person's chromosomal DNA. When associated with immune deficiency, chromosomal disorders may be linked to Down syndrome, CHARGE syndrome, DiGeorge Syndrome, and Cornelia de Lange syndrome, abnormalities of chromosomes 8 or 18.
What are the types of chromosomal disorders with immune deficiency?
DiGeorge Syndrome (DGS) is caused by abnormal migration and development of certain cells and tissues during fetal development. As part of the developmental defect, the thymus gland may be affected and T-lymphocyte production may be impaired, resulting in low T-lymphocyte numbers and frequent infections. Approximately 90 percent of patients with DGS have a small deletion in chromosome number 22 at position 22q11.2. Thus another name for this syndrome is the 22q11.2 deletion syndrome. Other names include velocardiofacial syndrome and conotruncal anomaly face syndrome.
Therapy for DGS is aimed at correcting the defects in the affected organs or tissues. Therefore, therapy depends on the nature of the different defects and their severity. Treatment of the low calcium and hypoparathyroidism may involve calcium supplementation and replacement of the missing parathyroid hormone. A heart defect may require medications or corrective surgery to improve the function of the heart. The need for therapy of the T-lymphocyte defect varies and depends on the extent of impaired T cell function.
Major features of CHARGE Syndrome are vision loss, narrowing of the passages that go from the back of the nose to the throat, cranial nerve abnormalities, short wide ears with small ear lobes, malformed middle ears with possible hearing loss, and balance problems. It results from a genetic mutation usually in the CHD7 gene.
Cornelia de Lange syndrome (CdLS) is characterized by distinctive facial features, growth retardation, hirsutism, upper limb abnormalities, cardiac defects, gastrointestinal dysfunction, hearing loss, myopia, and cryptorchidism or hypoplastic genitalia. Immune defects occur with this disorder, usually associated with recurrent infections and in some cases deficiencies in immunoglobulins and T cells.