All of the following are true about Frederich's ataxia except

*Friedreich's ataxia is most common; autosomal recessive, onset before age 25; ataxia with areflexia, upgoing toes, vibration and position sense deficits, cardiomyopathy, hammer toes, scoliosis; linked to expanded trinucleotide repeat in the intron of gene encoding frataxin; a second form is associated with genetically determined vitamin E deficiency syndrome. Common dominantly inherited ataxias are spinocerebellar ataxia (SCA)1 (olivopontocerebellar atrophy; "ataxin-1" gene) (Fig. 184-1), SCA2 (ataxin-2; pts from Cuba and India) and SCA3 (Machado-Joseph disease); all may manifest as ataxia with brainstem and/or extrapyramidal signs; SCA3 may also have dystonia and amyotrophy; genes for each disorder contain unstable trinucleotide repeats in coding region. Symptoms may include the following: 91% of people develop hea problems such as cardiomegaly (up to dilated cardiomyopathy), symmetrical hyperophy, hea murmurs, atrial fibrillation, tachycardia (fast hea rate), hyperophic cardiomyopathy) and conduction defects Cerebellar: nystagmus, fast saccadic eye movements, dysmetria, loss of coordination (truncal ataxia and Stomping gait) Vision impairment Hearing impairment Slurred speech Abnormal curvature of the spine Dorsal column: Loss of vibratory sensation and proprioceptive sensation occurs About 20% of people have trouble metabolizing carbohydrates and 10% develop diabetes mellitus Lower motor neuron lesion: absent deep tendon reflexes Pyramidal: extensor plantar responses, and distal weakness Muscle weakness in the arms and legs High plantar arches Ref Harrison20th edition pg 2765