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Short Quiz on Ataxia telengiectasia
Instruction
2. There is 1 Mark for each correct Answer
The gene responsible for Ataxia Telangiectasia is located on:
- This is a hereditary condition transmitted in the autosomal recessive mode
- combined immunodeficiency is associated with cerebellar ataxia, telangiectasia, ovarian dysgenesis & chromosomal abnormalities.
- Genetic features : Gene responsible on chromosome 11
- Gene product may play a role in DNA repair
- ATM gene encodes Atm protein kinase, a member of phosphatidyl inositol 3-kinase family
Clinical features :–
- ataxia & chorioathetoid movements noticed in infancy.
- Telangiectasia involving the conjuctiva & face appears at 5 or 6 years of age.
- The disease is progressive, with both neurological defects & immunodeficiency becoming severe with time.
- Death occurs due to sinopulmonary infection early in life , or malignancy in 2nd or 3rd decade.
| Friedreich\’s ataxia (autosomal recessive) | Ataxia, areflexia, extensor plantar responses, position sense deficits, cardiomyopathy, diabetes mellitus, scoliosis, foot deformities; optic atrophy; late-onset form, as late as 50 years with preserved deep tendon reflexes, slower progression, reduced skeletal deformities, associated with an intermediate number of GAA repeats and missense mutations in one allele of frataxin; genetic testing available |
Ref: Harrisons Principles of Internal Medicine, 18th Edition
DNA repair defect is seen in:
A, B & C i.e. Xeroderma pigmentatosa, Bloom\’s syndrome & Ataxia telangiectasia
Ataxia telangiectasia, Bloom\’s syndrome, Fanconi\’s anemia, Xeroderma pigmentosa, hereditary non polyposis colon cancer and few breast cancers are due to DNA repair defects.
Ans. is \’b\’ i.e., Ataxia telangiectasia
- Syndromes of defective DNA repair have such a high level of chromosomal instability that they are known as chromosome-breakage syndromes or chromosomal instability syndromes.
Answer is B (Decreased levels of a fetoproteins)
Persistance of very high levels of oncofetal proteins, including alpha fetoproteins and carcinoembryonic antigens is of diagnostic value – Harrison
All other features mentioned as options are characteristics of Ataxia-telengiectasia
Ataxia telangiectasia
o Ataxia Telangiectasia (AT) is an autosomal recessive disorder.
o It is due to mutation of AT gene located on chromosome 11.
o There is defective DNA repair that results in multiple chromosomal breaks.
Clinical manifestations
o Present in first decase of life.
o Feature are : –
i) Oculocutaneous telengiectasia
ii)Neurological -4 Ataxia, dysarthria, extensor plantar response, myoclonic jerks, areflexia, distal sensory deficity.
iii) Immunodeficeincy —) Thymic hypoplasia with cellular and humoral (IgA and IgG2) immunodeficeincy.
iv) Recurrent pulmonary infections
v) Endocrine disorders —> Tye I DM
vi) Premature aging
vii) Malignancies Lymphoma, Hodgkin\’s disease, acute T cell leukemia, breast cancer.
and a-feto protein and carcino-embryonic antigen are increased
Which is the only phacomatosis to be inherited on an autosomal recessive basis:
Ans. Ataxia-telangiectasia