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P432 Encephalopathy in teenagers – a challenging etiologic diagnosis

Introduction Inherited metabolic disorders due to intoxication provoked by highly toxic endogenous compounds are among the causes of encephalopathy. That is the case of urea cycle disorders in which ammonia’s great neurotoxicity can frequently be lethal. Ornithine Transcarbamylase (OTC) Deficiency is an X-link genetic disorder and the most common disorder of the urea cycle. Presentation in heterozygote females is variable and can go from being asymptomatic to having mild chronic symptoms with severe exacerbations in any age. Case report Fifteen year old female with sporadic headache since the age twelve without other relevant medical history. Due to persistent frontoparietal headache for two weeks, she was given topiramate. Despite medication, the headache worsened and dizziness, blurred vision, dysarthria, aphasia, asterixis, motor incoordination and lethargy developed. Trauma, recent infections or toxic ingestions were denied. Diagnostic workup in a private hospital with laboratory studies including urine toxic screening, complete blood count, hepatic and renal function and cerebral MRI were normal. On account of a suspected iatrogenic cause for encephalopathy, topiramate was suspended after two days and the patient was referred to a Pediatric Emergency Department. On admission CSF study was normal but blood tests showed hyperammonemia (229 µmol/L) with latter increase to (359 µmol/L) despite treating measures (endovenous fluids and discontinuation of protein intake); She was given sodium benzoate, sodium phenylbutyrate and arginine resulting in blood levels of ammonia returning to normal. The demonstration of elevated urinary orotic acid led to the probable diagnosis of OTC deficiency which was later confirmed by molecular diagnosis. Discussion Serum ammonia levels sould be measured in every patient with unexplained altered mental status. Primary (urea clycle disorders) and secondary hyperammonemia alike are considered emergency situations therefore, treatment should never be delayed by diagnostic tests. On the other hand, both treatment and exacerbation preventions have an impact in prognosis regardless of age.