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Chromosome 22q 11.2 deletion syndrome md pathology exam give answer based on robbins

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Robbins pathology 22q11.2 deletion syndrome DiGeorge syndrome features

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Chromosome 22q11.2 Deletion Syndrome

22q11.2 deletion syndrome is a spectrum of disorders caused by a small interstitial microdeletion at 22q11.2 on the long arm of chromosome 22. It unifies conditions previously described as DiGeorge syndrome and velocardiofacial syndrome.

Clinical features

  • Congenital cardiac defects, especially conotruncal/outflow tract defects
    • Tetralogy of Fallot
    • Truncus arteriosus
    • Interrupted aortic arch
    • Ventricular septal defect
  • Palatal abnormalities: cleft palate or velopharyngeal insufficiency
  • Characteristic facial dysmorphism
  • Developmental delay and learning difficulties
  • Thymic hypoplasia leading to impaired T-cell mediated immunity and recurrent infections
  • Parathyroid hypoplasia causing hypocalcemia, which may produce tetany or seizures
  • Increased risk of psychiatric illness, particularly schizophrenia and bipolar disorder. Robbins states that schizophrenia develops in about 25% of affected adults.

Phenotypic variants

  1. DiGeorge syndrome
    • Dominant manifestations are:
      • Thymic hypoplasia/aplasia with T-cell immunodeficiency
      • Parathyroid hypoplasia with hypocalcemia
  2. Velocardiofacial syndrome
    • Usually milder immunodeficiency
    • More marked facial dysmorphism, palatal defects, and cardiac anomalies
The variable presentation is attributed to differences in the size and position of the 22q11.2 deletion.

Diagnosis

  • Suspected clinically from the combination of cardiac defect, hypocalcemia, immunodeficiency, facial/palatal abnormalities, and developmental delay.
  • Confirmed by demonstrating the deletion, classically by fluorescence in situ hybridization (FISH). Chromosomal microarray is also used in current practice.

Exam mnemonic

CATCH-22
  • Cardiac defects
  • Abnormal facies
  • Thymic hypoplasia
  • Cleft palate
  • Hypocalcemia
  • 22q11.2 deletion
Source: Robbins & Kumar Basic Pathology, section “22q11.2 Deletion Syndrome,” p. 127.
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