Microdeletion Syndromes Flashcards
What is microdeletion syndrome?
Chromosomal deletions that are too small to be seen microscopically
But it involves 2 or more adjacent genes
Investigation of choice
(How are they detected?)
FISH (Fluoroscent In Situ Hybridization) using specific fluorescent probes
But now more frequently identified through:
Array comparative genomic hybridisation OR
other methods of genome wide testing
Common examples of microdeletion syndromes
DiGeorge syndrome
Williams syndrome
Microdeletion in DiGeorge syndrome
22q11
(Chromosome 22, long arm q, location 11)
How is the deletion inherited in DiGeorge syndrome?
From phenotypically normal parents
(demonstrates variable effect of this deletion)
Features in neck of DiGeorge syndrome
Parathyroid gland hypoplasia
Thymus hypoplasia
Outcome of parathyroid hypoplasia in DiGeorge syndrome
Low PTH
Low calcium (Hypocalcaemia)
Outcome of thymus hypoplasia in DiGeorge syndrome
Low T lymphocytes
Congenital cardiac malformation in DiGeorge syndrome
Outflow tract anomalies
Particularly, interrupted aortic arch and truncus arteriosus
Facial feature of DiGeorge syndrome
Cleft palate
Cognitive features of DiGeorge syndrome
Learning disability
Increased psychiatric disorders
particularly, Schizophrenic spectrum
Microdeletion in Williams syndrome
Microdeletion of ‘elastin’ gene on chromosome 7
How is deletion inherited in Williams syndrome?
Deletions occur anew;
because, people with Williams are unlikely to have their own children
Cognitive features of Williams syndrome
Learning disability
Chatty
Social behaviour: known as >> Cocktail party manner
Eye feature in Williams syndrome
Stellate iridis
