P147 – 2569: Adenylosuccinate lyase deficiency presenting as a paroxysmal movement disorder

Objective To describe an atypical presentation of the Adenylosuccinate lyase (ADSL) deficiency syndrome. Methods A three year-old boy presented to our clinic because of intractable epilepsy. At the age of 10 months he had a single episode of status epilepticus. At the age of 16 months recurrent episodes of rapid semi-rhythmic jerking movements occurred, involving mostly the upper limbs and spreading homolaterally or contralaterally to other body parts. These attacks started without any apparent trigger, lasted up to a few hours, constantly disappeared during sleep and returned a few minutes after awakening. There was no change of consciousness or behavior. Some of the paroxysms were accompanied by dystonic limb or neck posturing. Ictal Electroencephalogram (EEG) did not show epileptic activity. Ictal surface Electromyography (EMG) demonstrated irregular bursts lasting less than 50 msec. with a frequency of 14 Hz. Results Whole exome sequencing revealed homozygous mutations in the ADSL gene. The diagnosis was confirmed by highly elevated urine succinyladenosine. Treatment with ketogenic diet significantly improved these paroxysmal attacks. Conclusion ADSL deficiency is a defect of purine metabolism. The disorder can present with a wide spectrum of symptoms. Epilepsy, usually intractable is the most constant feature. Our patient has a unique phenotype: only one unprovoked seizure and a paroxysmal movement disorder which is the most predominant feature.