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Table 1 Clinical signs and symptoms of acute and chronic presentations of UCDs, and triggering factors for hyperammonemia in UCD patients

From: Suggested guidelines for the diagnosis and management of urea cycle disorders

Acute presentation Chronic presentation
· Altered level of consciousness (from somnolence and lethargy to coma) mimicking encephalitis or drug intoxication · Confusion, lethargy, dizziness
  · Migraine-like headaches, tremor, ataxia, dysarthria
· Acute encephalopathy (see below) · Asterixis (in adults)
· Seizures (generally not isolated but along with an altered level of consciousness) · Learning disabilities, neurodevelopmental delay, mental retardation
· Ataxia (generally associated with altered consciousness level) · Chorea, cerebral palsy
· Stroke-like episodes · Protracted cortical visual loss
· Transient visual loss · Progressive spastic diplegia or quadriplegia (described in ARG1D and HHH syndrome)
· Vomiting and progressive poor appetite · Protein aversion, self-selected low-protein diet
· Liver failure · Abdominal pain, vomiting
· Multiorgan failure · Failure to thrive
· Peripheral circulatory failure · Hepatomegaly, elevated liver enzymes
· “Post-partum psychosis” · Psychiatric symptoms: hyperactivity, mood alteration, behavioural changes, aggressiveness
· Psychiatric symptoms (hallucinations, paranoia, mania, emotional or personality changes) · Self-injurious behaviour
  · Autism-like symptoms
 In neonates:  · Fragile hair (typical for ASLD)
· sepsis-like picture, temperature instability
· respiratory distress, hyperventilation
· Dermatitis
  · Specific neuropsychological phenotype in heterozygous OTC females
  · Episodic character of signs and symptoms
Potential triggers of hyperammonemic crises in UCD patients
· Infections
· Fever
· Vomiting
· Gastrointestinal or internal bleeding
· Decreased energy or protein intake (e.g. fasting pre surgery, major weight loss in neonates)
· Catabolism and involution of the uterus during the postpartum period (mostly OTC females)
· Chemotherapy, high-dose glucocorticoids
· Prolonged or intense physical exercise
· Surgery under general anesthesia
· Unusual protein load (e.g. a barbecue, parenteral nutrition)
· Drugs: Mainly valproate and L-asparaginase/pegaspargase. Topiramate, carbamazepine, phenobarbitone, phenytoine, primidone, furosemide, hydrochlorothiazide and salicylates have also been associated with hyperammonemic decompensation.
  1. Typical and uncommon signs and symptoms are highlighted in bold- and normal-type, respectively, whereas italic type marks signs and symptoms reported in single patients. Grade of recommendation, D.