Variant ataxia telangiectasia
Citation, DOI and case data
Acute right-sided weakness and headache. Past medical history included long-standing generalized dystonia including retrocollis with progressive upper and lower limb dystonia. On examination, he had poor balance and mobility, his head was turned back and to the left and he had difficulty with pronunciation. Scleral telangiectasia was noted.
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1.4cm ovoid mixed T2 hypo/hyper-intense focus in the periventricular white matter of the left frontal lobe.
Diffuse bilateral T2 hyperintense signal in the deep and periventricular white matter of the cerebral hemispheres.
1.4cm ovoid mixed FLAIR hypo/hyper-intense focus in the periventricular white matter of the left frontal lobe.
Diffuse bilateral FLAIR hyperintense signal in the deep and periventricular white matter of the cerebral hemispheres.
Axial DWI B1000
1.4cm focus of high signal in the periventricular white matter of the left frontal lobe consistent with abnormal restricted diffusion and suspicious for an acute infarct or intraparenchymal hematoma.
Axial ADC Map
ADC map confirms a focus of abnormal restricted diffusion in the periventricular white matter of the left frontal lobe, suspicious for an acute infarct or intraparenchymal hematoma.
T1 hyperintense focus in the periventricular white matter of the left frontal lobe which correlates to the previously identified focus of abnormal restricted diffusion and mixed T2/FLAIR hyper/hypo-intense signal constant with an acute intraparenchymal hematoma.
SWI demonstrates diffuse bilateral hypointensities consistent with microhemorrhages in the periventricular and deep white matter of the cerebral and cerebellar hemispheres, with relative sparing of the juxtacortical white matter and brainstem. The acute left frontal intraparenchymal hematoma is also identified.
Sagittal T2 weighted images demonstrate pronounced atrophy of the cerebellum, most marked in the vermis. Again noted is an ovoid mixed T2 hypo/hyper-intense focus in the periventricular white matter of the left frontal lobe and diffuse bilateral T2 hyperintense signal in the deep and periventricular white matter of the cerebral hemispheres.
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Figure 1. Western blot analysis of a lymphoblastic cell line from the patient's blood (column 11) demonstrates a greatly reduced level of ATM protein consistent with Ataxia Telangiectasia. Column 2 demonstrates complete absence of ATM protein in a patient with classic AT.
AOA2 (ataxia oculomotor apraxia type 2).
Figure 2. Patient's blood was exposed to 1 Gray of gamma rays. Chromosomal radiosensitivity of the T lymphocytes was exposed. There were 26 cells with 21 bits of damage compared with 8 bits of damage in the normal control in 50 cells consistent with a moderate increase in chromosomal radiosensitivity. In classic AT, a 5-10 fold increased level of gamma ray induced chromosome damage is expected.
Ataxia telangiectasia (AT) is a rare autosomal recessive neurodegenerative multisystem disorder caused by two truncating ATM gene mutations leading to total loss of ATM kinase activity and, therefore, function of the ATM protein 1. In less severe cases, termed AT variants, there is retention of some ATM kinase activity due to either expression of very low levels of normal ATM protein (from splice site mutations) or expression of mutant ATM (from missense mutations) 2.
AT variants are a phenotypically heterogeneous group, characterized by slower progression of clinical signs, an extended lifespan compared to most patients with the classical form of the disease with less cellular sensitivity to radiation, susceptibility to malignancies and recurrent sinopulmonary infection.
In the absence of clinical history, this case demonstrates a radiologic diagnostic conundrum. The most striking abnormality is the presence of diffuse bilateral microhemorrhages with a superimposed acute intraparenchymal hematoma and cerebral amyloid angiopathy would be high on the list of differentials. However, the presence of extensive bilateral T2/FlAIR hyperintense signal within the white matter seems disproportionate to the degree of likely concomitant small vessel disease. Given that this is a case of an adult brain, the diagnosis of AT may elude the radiologist as patients with the classic form of AT usually do not survive beyond childhood. The presence of diffuse white matter T2/FLAIR signal abnormality and disproportionate cerebellar atrophy clinches the diagnosis of variant ataxic telangiectasia.
- 1.Taylor AM, Byrd PJ. Molecular pathology of ataxia telangiectasia. Journal of clinical pathology. 2005;58:1009-1015
- 2. McConville CM, Stankovic T, Byrd PJ, McGuire GM, Yao QY, Lennox GG, et al. Mutations associated with variant phenotypes in ataxia-telangiectasia. American journal of human genetics. 1996;59:320-330
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