Genetics Article

Micro-deletion syndromes

Di- George syndrome


Deletion of part of the lengthy arm in chromosome twenty-two at site 22q11. 2(1) The most common removal includes the  TBX1 gene (85% individuals), see figure 1 below. Defect in neural-crest tissue (thyroid, thymus, and conotruncal septum of the heart) due removal of region in chromosome 22 (2) Inheritance routine is autosomal dominant (2)

Hypoplasia of thymus and parathyroid glands resulting in hypocalcemia Acronym CATCH22 is used with this syndrome (Cardiac Abnormality/abnormal facies, T cellular deficit due to thymic hypoplasia, Cleft taste, Hypocalcemia ) (2)� a variation in the phenotype and deletion could be in equally maternal or perhaps paternal source (1)

Determine 1: shows the hereditary map of chromosomal place 22q11. two, 85% individuals have a huge 3-Mb deletion (40 genes) (3).

Clinical features (1)

Heart failure malformations (aortic arch anomalies)

Dysmorphic face features (low set the ears, upward and downward slanting eyes, small mouth) (2) Recurrent infections

Neonatal hypocalcaemia – tetany /Seizures

Investigations (3)

Chest Radiography – thymus

FISH (fluorescent in situ hybridisation) the probe TUPLE1 and N25 are used for breakpoints in the region Incidence (4)

1 in 4000 of population (international)


1) Connor, J. and Ferguson-Smith, Meters. (1997).  Essential medical inherited genes. 1st education. Oxford [England]: Blackwell Science. 2) Omim. org, (2014).  OMIM Entry - # 188400 - DIGEORGE SYNDROME; DGS. [online] Offered by: [Accessed a couple of Jun. 2014]. 3) Roberta A Pagon, E. (2014).  22q11. 2 Deletion Affliction - GeneReviews® - NCBI Bookshelf. [online] Ncbi. nlm. nih. gov. Available at: [Accessed 2 Jun. 2014]. 4) Emedicine. medscape. com, (2014).  Medscape: Medscape Access. [online] Available at: [Accessed 2 Jun. 2014]. Prader Willi symptoms (PWS)

Aetiology (1)

73% show a microdeletion for 15q11-q13, and remaining 25% shows mother's uniparental disomy ( deficiency of paternal genes) Deletion is mainly paternal in origin

Loss of function of genes in this region, maternal genes happen to be inactive There are two types of deletions- " Type 1 deletions (T1D) extend coming from BP1 to BP3 and type a couple of deletions (T2D) extend from BP2 to BP3”, find Figure you below (3).

Figure 2: reveals genetic and expression map of chromosomal region 15q11. 2-q13 (3)

Clinical features (3)

Hypotonia, (late childhood this kind of improves)


Smooth face, tented upper lip, visible forehead

Hypoplastic external genitalia

Palpebral cracks are salted peanuts shaped

Small toes and hands

Low mental IQ (20-80)

Incidence (3)

1 in 10, 500 live births

Reoccurrence risks (3)

2% reoccurrence risk due parental strength arrangement

Investigations (2)

CFISH analysis with the SNRPN probe

chromosomal microarrays, discover size of removal

Reference point:

1 . Omim. org, (2014).  OMIM Entry - # 176270 - PRADER-WILLI SYNDROME; PWS. [online] Available at: [Accessed two Jun. 2014]. 2 . Roberta A Pagon, S. (2014).  Prader-Willi Symptoms - GeneReviews® - NCBI Bookshelf. [online] Ncbi. nlm. nih. gov. Available at: [Accessed 2 Jun. 2014]. 3. Connor, J. and Ferguson-Smith, M. (1997).  Essential medical genetics. initial ed. Oxford [England]: Blackwell Technology. Angelman syndrome (Happy puppet syndrome)

Aetiology (1)

75% show microdeletion at 15q12

Deleted region is mostly maternal in origin

5% shows paternal uniparental disomy

Remaining 20% show unfamiliar molecular pathology

Qualifications (2)

Infants do not display phenotype

Onset of early expansion delay about 6 months

Clinical features (3)

Development delay

Poor conversation

Jerky movements

Paroxysms of inappropriate laughters

Dysmorphic face features...

Sources: 1) Roberta A Pagon, B. (2014).  Retinoblastoma -- GeneReviews® -- NCBI Bookshelf. [online] Ncbi. nlm. nih. gov. Offered at: [Accessed two Jun. 2014].

2) Omim. org, (2014).  OMIM Entry - # 613884 -- CHROMOSOME 13q14 DELETION SYMPTOMS. [online] Offered by: [Accessed a couple of Jun. 2014].

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