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