Monday 30 May 2011

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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