Louis-Bar syndrome


Clinical Characteristics
Ocular Features: 

The ocular manifestations are striking although of little clinical consequence.  The conjunctivae have prominent telangiectases which usually develop between 3 and 5 years of age.  These apparently do not occur intraocularly.    Oculomotor apraxia is often an earlier sign consisting of difficulty in initiation of smooth pursuit movements which patients may modify by head motion in the direction of attempted gaze.  This aspect can be helpful in diagnosis of AT in young children with cerebellar ataxia. 

Systemic Features: 

Telangiectases are often found in the pinnae, on the cheeks, and on the forearms, usually after the onset of neurological signs.  However, this is also a disorder with multiple systemic signs, the most serious of which are unusual sensitivity to ionizing radiation, excessive chromosomal breakage, a deficiency in the immune system, mild cognitive impairment, and increased risk of malignancies.  Lymphomas, often of B-cell origin, and leukemia, usually of T-cell origin, are the most common malignancies but there is a significantly increased risk of breast cancer as well. Serum IgG2 and IgA levels are often reduced and sinopulmonary infections are common.  Serum alpha-fetoprotein levels are usually increased.  The ataxia is progressive and often begins as truncal unsteadiness with limbs involved later.  It is often accompanied by choreoathetosis and/or dystonia which may result in severe disability by the second decade.  Life span is shortened and many patients succumb to their disease by the 3rd and 4th decades. 

In some famiies with confirmed mutations in ATM the disorder presents with signs of primary torsion dystonia and myoclonus-dystonia.  These signs may resemble an apparent autosomal dominant pattern with parent-child transmission.  It is unclear whether these families represent a variant of AT or a unique disorder.  The latter is suggested by an earlier onset of signs, the lack of cerebellar atrophy,  and the absence of ataxia and ocular telangiectases on initial presentation.  The risk of malignancies in these famiies is high.

Some of these signs have been reported in milder form among heterozygous carriers as well.  The most serious is an increased risk of malignancy, perhaps as much as 6.1 times that of non-carriers.  This combined with the inherent sensitivity to ionizing radiation has led to the suggestion that X-rays should be used with caution, especially when considering mammograms among female relatives.



This is an autosomal recessive disorder as a result of mutations in the ATM gene located at 11q22-q23.  Affected offspring of consanguineous matings are often homozygous for this mutation whereas those from unrelated parents are usually compound heterozygotes.  There is some evidence of genetic heterogeneity based on both clinical and DNA studies (AT variants).

Other conditions with oculomotor apraxia are: ataxia with oculomotor apraxia 1 (208920), ataxia with oculomotor apraxia 2 (602600), and Cogan type oculomotor apraxia (257550) which lacks other neurologic signs. Oculomotor apraxia may be the presenting sign in Gaucher disease (230800, 230900, 231000).

Autosomal recessive
Treatment Options: 

No treatment is known for the neurologic manifestations.  However, patients and first degree relatives should be monitored for malignancies.  Childhood vaccinations may lead to widespread viral dissemination as a consequence of the immune defect.

Article Title: 

Ataxia telangiectasia: a review

Rothblum-Oviatt C, Wright J, Lefton-Greif MA, McGrath-Morrow SA, Crawford TO, Lederman HM. Ataxia telangiectasia: a review. Orphanet J Rare Dis. 2016 Nov 25;11(1):159. Review.

PubMed ID: 

Cognitive Phenotype in Ataxia-Telangiectasia

Hoche F, Frankenberg E, Rambow J, Theis M, Harding JA, Qirshi M, Seidel K, Barbosa-Sicard E, Porto L, Schmahmann JD, Kieslich M. Cognitive Phenotype in Ataxia-Telangiectasia. Pediatr Neurol. 2014 May 5.

PubMed ID: 

Variant ataxia-telangiectasia presenting as primary-appearing dystonia in Canadian Mennonites

Saunders-Pullman R, Raymond D, Stoessl AJ, Hobson D, Nakamura T, Pullman S, Lefton D, Okun MS, Uitti R, Sachdev R, Stanley K, San Luciano M, Hagenah J, Gatti R, Ozelius LJ, Bressman SB. Variant ataxia-telangiectasia presenting as primary-appearing dystonia in Canadian Mennonites. Neurology. 2012 Feb 15. [Epub ahead of print] PubMed PMID: 22345219.

PubMed ID: 
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