Progressive ataxia associated with ocular apraxia type 1 (AOA1) with a presence of a novel mutation on the aprataxin gene
This patient was a 17-year-old right-handed male of Afghani descent who developed progressive ataxia. His symptoms first started at age 10 when he developed dysarthria with scanning of speech, and he began to lose his balance as well as the ability to co-ordinate his movements. A former soccer player on his school team, he could no longer participate in the sport and in other athletic activities. He began to fall once or twice-a-day, and his typing and writing skills started to deteriorate due to lack of fine motor skills. In addition, he began to report difficulty in swallowing with frequent choking spells.\nBorn with no complications at birth, he started walking at 10 months, said his first words at 12 months, ran at age 2, and rode a bike at age 5. He has 3 sisters and a brother who are all healthy. The family is consanguineous as his parents are first cousins.\nAt age 13, he had his first neurological assessment where he was found to have slow speech with low volume. He had a moderate amplitude kinetic tremor of both upper extremities with target dysmetria on finger-nose-finger testing, as well as heal-knee-shin testing and dysdiadochokinesis. He had a wide-based, unsteady gait and was unable to stand with feet together for more than a few seconds. The rest of his neurological examination was unremarkable.\nInvestigations included complete blood count, serum electrolytes including calcium, magnesium, phosphorus, liver function tests, and a complete thyroid panel. An MRI of the brain revealed that he had an abnormal hypoplastic cerebellum as shown in . Testing of somatosensory-evoked potentials and brainstem auditory response were both normal. Nerve conduction studies and electromyography were also both normal. However, his visual evoked potential was found to be abnormal upon binocular and monocular testing due to a low amplitude response.\nGenetic testing for FDRA and spinocerebellar ataxia (SCA1, SCA2, SCA3, SCA6, SCA7, SCA8, SCA17) were found to be negative. However, DNA sequencing for AOA1 showed a mutation on the APTX gene. The mutation consists of a homozygous deletion of thymine at position 12 of IVS4 (IVS4-12delT). This specific mutation on the APTX gene has never been reported in the medical literature. Molecular testing of his parents showed that both of them were heterozygous for the same mutation and as a result, did not manifest any of the symptoms of ataxia at the time. His mother and father were 49 and 55 years of ages, respectively. His abnormal visual evoked potentials may be suggestive of ocular involvement, although it was not appreciated on history or physical examination.