DiGeorge Syndrome (22q11.2 Deletion Syndrome)

Other Names / Associations:

• 22q11.2 deletion syndrome
• Congenital thymic aplasia
• Conotruncal anomaly face syndrome
• DiGeorge syndrome
• DiGeorge anomaly
• Shprintzen syndrome
• Strong syndrome
• Thymic hypoplasia
• Velo-cardio-facial syndrome

DiGeorge Syndrome Facts:

• Syndrome caused by the deletion of a small piece of chromosome 22, near the middle, at location q11.2.
• Absent thymus gland is main clinical finding.
• Defect in the development of the 3rd & 4th branchial pouches & arches.
• Presents in childhood or adulthood.
• Non-familial rare disorder with prevalence estimated at 1:4000.
• Condition described in 1968 by the pediatric endocrinologist Angelo DiGeorge.

DiGeorge Clinical Features:

• Cardiovascular defects - esp conotruncal malformations (tetralogy of Fallot, interrupted aortic arch, ventricular septal defect, & persistent truncus arteriosus); prolonged QT syndrome (hypocalcaemia).
• Palatal abnormalities - particularly velopharyngeal incompetence (VPI), submucosal cleft palate, & cleft palate; feeding problems.
• Facial abnormalities - esp Caucasian individuals) including hypertelorism.
• Opportunistic infections - thymic hypoplasia
• Endocrine - Hypoparathyroidism (hypocalcaemia), growth hormone deficiency
• ENT - hearing loss (both conductive & sensorineural), laryngotracheoesophageal anomalies
• Neuropsychiatric - learning difficulties, seizures (+/- hypocalcaemia), psychiatric disorders.
• Autoimmune disorders
• Skeletal abnormalities
• Renal anomalies

CATCH-22 Mnemonic:

• DiGeorge features can be summarized using the mnemonic CATCH-22:
• C - Cardiac abnormality (esp tetralogy of Fallot)
• A - Abnormal facies
• T - Thymic aplasia
• C - Cleft palate
• H - Hypocalcaemia
• 22 - Chromosome 22

Pathophysiology:

• Reduction in T-cell number & function.
• B-cell function is often completely normal.
• The exact mechanism causing all of the associated features of DiGeorge syndrome is unknown.
• The 22q11.2 deletion may involve migration defects of neural crest-derived tissues, particularly affecting development of the 3rd & 4th branchial pouches.
• As a result the thymus gland & the parathyroid glands are affected.

Image: Web image multiple sites.

Tags: 22q11.2 Deletion Syndrome - Branchial Pouch - Cleft Palate - DiGeorge Syndrome - Hypoparathyroidism - Microdeletion - Thymic Aplasia - Velo-cardio-facial Syndrome
Posted by Medicalchemy
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