Differential diagnoses of classic ataxia telangiectasia.3 5 AD, autosomal dominant; AR, autosomal recessive
| Syndrome | Gene | Inheritance pattern | Clinical features |
| Abetalipoproteinaemia | MTTP | AR | Ataxia, steatorrhoea, muscle weakness, cognitive delay |
| Autosomal recessive ataxia of Charlevoix Saguenay (ARSACS) | SACS | AR | Ataxia, polyneuropathy, spasticity, amyotrophy |
| Ataxia with oculomotor apraxia-1 (AOA1) | APTX | AR | Ataxia, oculomotor apraxia, peripheral neuropathy, childhood-onset. No immunodeficiency and no telangiectasia, hypoalbuminaemia, secondary coenzyme Q10 deficiency |
| Friedreich’s ataxia | FXN | AR | Most common inherited ataxia. Young-onset ataxia, peripheral neuropathy, absent reflexes, extensor plantar responses, reduced proprioception and vibration, cardiac hypertrophy, thin retinal nerve fibre layer, diabetes |
| Giant axonal neuropathy | GAN | AR | Sensorimotor neuropathy, ataxia, tight curly hair, cognitive impairment |
| Infantile-onset spinocerebellar ataxia (IOSCA)/mitochondrial depletion syndrome 7 | TWNK | AR | Ophthalmoplegia, optic atrophy, peripheral neuropathy, athetosis, deafness, loss of ambulation by adolescence |
| Joubert’s syndrome | OFD1 | AR | Ataxia, oculomotor apraxia, hypotonia, apnoea, molar tooth sign on MRI |
| Leukodystrophies: Alexander’s disease, Canavan’s disease, Metachromatic leukodystrophy, Krabbe’s disease | GFAP ASPA ASA GALC | AD AR AR AR | Ataxia, peripheral neuropathy, cognitive impairment, seizures, white matter lesions |
| Childhood-onset myoclonic dystonia | GNB1, KCTD1 | AD | Myoclonic seizures, learning disability, growth delay, gastrointestinal abnormalities, dystonia |
| Nijmegen Breakage Syndrome (NBS) | NBN | AR | Microcephaly, immunodeficiency and cancer predisposition |
| Radiosensitivity, immunodeficiency, dysmorphic features, learning difficulties (RIDDLE) | RNF168 | AR | Ocular telangiectasia, immunodeficiency, ataxia, learning difficulties, short stature, microcephaly |
| Xeroderma pigmentosum (XP) | XPA - XPG | AR | Extreme sensitivity to UV light, telangiectasia, skin cancers, ataxia, growth retardation, sensorineural hearing loss and neuropathy |