Pathophysiology
1) genetic disorder, usually presenting at age 0-10 years 2) cerebellar malfunctioning 3) strong association with cancer 4) oculocutaneous telangiectasia 5) malfunctioning immune system
Signs and Symptoms
1) spider angiomas 2) cerebellar dysfunction with staggering-type gait 3) growth retardation 4) recurrent pulmonary infections 5) nystagmus 6) linear telangiectasias initially appearing on bulbar conjunctiva 7) telangiectasias progress to butterfly pattern on ears, eyelids, and cheeks 8) dysarthria 9) myoclonic jerks 10) areflexia 11) sensory deficits 12) premature aging
Characteristic Test Findings
Laboratory – 1) decreased lymphocyte count 2) antibodies to insulin receptor 3) presence of alpha fetoprotein 4) presence of carcinoembryonic antigen 5) decreased number of T cells 6) decreased levels of IgE and IgA
Histology/Gross Pathology
1) loss of Purkinje , basket, and granule cells in cerebellar cortex 2) loss of anterior horn cells in spinal cord and dorsal columns
Associated Conditions
1) lymphomas (especially Hodgkin’s lymphoma) 2) leukemia 3) gastric cancer 4) brain tumors 5) breast cancer 6) hypoplastic thymus 7) diabetes with severe insulin resistance 8) ovarian agenesis 9) infertility 10) hypersensitive to ionizing radiation 11) decreased pituitary functioning 12) adrenal cortical hyperplasia
Biochemistry
1) deficient functioning of both B and T cells 2) defective nuclear phophoprotein cannot respond to DNA damage
Inheritance/Epidemiology
1) autosomal recessive 2) defective ATM gene is on chromosome 11 (11q22-q23) 3) occurs in 1/50,000 4) heterozygotes have increased risk of breast cancer
Treatment
1) avoidance of live vaccines 2) avoidance of blood products with T cells 3) avoidance of exogenous radiation 4) consider prophylaxis for Pneumocystis carinii with trimethoprim-sulfamthoxazole
Tips for USMLE
1) incidence of cancer is increased 100-fold 2) ataxia-telangiectasia is both a T cell and B cell problem 3) DNA damage cannot be repaired
shashank says
Here is a link to more information about the genetics of Ataxia Telangiectasia that was prepared by our genetic counselor and which has links to some useful resources for those dealing with this condition: http://sites/insidesurgery.com/files.accessdna.com/condition/Ataxia_Telangiectasia/47. There is also a phone number listed if you need to speak to a genetic counselor by phone. I hope it helps. Thanks, AccessDNA