Disruption of SOX6 is associated with a rapid-onset dopa-responsive movement disorder, delayed development, and dysmorphic features.

BACKGROUND: Sox6 is a transcription factor that is crucial for the differentiation and development of cortical interneurons and dopaminergic neurons of the substantia nigra pars compact. Loss-of-function mutations might thus result in complex paroxysmal diseases such as epilepsy syndromes or movement disorders. PATIENT: We present a 15-year-old boy with delayed speech development and attention deficit hyperactivity disorder who presented with a rapid-onset generalized dopa-responsive dystonia. RESULTS: Neurological examination revealed generalized dystonic and frequent athetoid movements of the arms, trunk, and neck. Gait was severely impaired secondary to frequent dystonic postures. Both a resting tremor and action tremors were observed in both hands. Speech was dysarthric but language comprehension was unimpaired. Testing for saccadic dysfunction revealed hypometric horizontal and vertical saccades. Physical examination was otherwise significant for a pectus carinatum and splenomegaly. Laboratory studies, brain magnetic resonance imaging, and electroencephalography were unremarkable. Treatment with levodopa/carbidopa led to a complete and sustained remission of neurological symptoms. Genetic testing revealed a mono-allelic de novo 84-kb deletion on chromosome 11p15.2 encompassing exons 14-16 of the SOX6 gene (chr11: 15944880-16029095, NCBI 37/hg19). CONCLUSIONS: This is the first report of a dopa-responsive movement disorder associated with SOX6 disruption. SOX6 mutations should be considered in the differential diagnosis of unexplained dopa-responsive dystonia syndromes.

Clinical and molecular characterisation of hereditary dopamine transporter deficiency syndrome: an observational cohort and experimental study.

BACKGROUND: dopamine transporter deficiency syndrome is the first identified parkinsonian disorder caused by genetic alterations of the dopamine transporter. We describe a cohort of children with mutations in the gene encoding the dopamine transporter (SLC6A3) with the aim to improve clinical and molecular characterisation, reduce diagnostic delay and misdiagnosis, and provide insights into the pathophysiological mechanisms. METHODS: 11 children with a biochemical profile suggestive of dopamine transporter deficiency syndrome were enrolled from seven paediatric neurology centres in the UK, Germany, and the USA from February, 2009, and studied until June, 2010. The syndrome was characterised by detailed clinical phenotyping, biochemical and neuroradiological studies, and SLC6A3 mutation analysis. Mutant constructs of human dopamine transporter were used for in-vitro functional analysis of dopamine uptake and cocaine-analogue binding. FINDINGS: children presented in infancy (median age 2·5 months, range 0·5-7) with either hyperkinesia (n=5), parkinsonism (n=4), or a mixed hyperkinetic and hypokinetic movement disorder (n=2). Seven children had been initially misdiagnosed with cerebral palsy. During childhood, patients developed severe parkinsonism-dystonia associated with an eye movement disorder and pyramidal tract features. All children had raised ratios of homovanillic acid to 5-hydroxyindoleacetic acid in cerebrospinal fluid, of range 5·0-13·2 (normal range 1·3-4·0). Homozygous or compound heterozygous SLC6A3 mutations were detected in all cases. Loss of function in all missense variants was recorded from in-vitro functional studies, and was supported by the findings of single photon emission CT DaTSCAN imaging in one patient, which showed complete loss of dopamine transporter activity in the basal nuclei. INTERPRETATION: dopamine transporter deficiency syndrome is a newly recognised, autosomal recessive disorder related to impaired dopamine transporter function. Careful characterisation of patients with this disorder should provide novel insights into the complex role of dopamine homoeostasis in human disease, and understanding of the pathophysiology could help to drive drug development.

Beta-ureidopropionase deficiency presenting with febrile status epilepticus.

UNLABELLED: Beta-ureidopropionase is the third enzyme in the catabolic pathway of uracil and thymine. To date, only three other patients are reported with this inborn error of metabolism. We report the clinical presentation of a male patient who presented at the age of 4 months after an ALTE-like event (ALTE = acute life-threatening event) with febrile status epilepticus. Such a clinical presentation has not been reported before in this condition. Diagnosis was based on biochemical, enzymatic and molecular studies. MRI (magnetic resonance imaging) at the age of 11 months demonstrated large subdural hematomata and global supratentorial atrophy. At that time the patient showed severe psychomotor retardation with muscular hypotonia, extremely limited visual contact and poorly controlled epilepsy. CONCLUSIONS: Pyrimidine degradation defects should be included in the differential diagnosis of convulsions, (febrile) status epilepticus, psychomotor retardation and possibly also ALTE-like events.