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Initial presentation of a urea cycle disorder in adulthood: an under-recognised cause of severe neurological dysfunction

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Clinical record

Two patients with ornithine transcarbamylase deficiency, a urea cycle disorder, were transferred to our intensive care unit within 12 months. Both were previously healthy men who initially presented with nondescript but progressive neurological symptoms after minor procedures (case summaries in Box 1).

Each patient developed their initial neurological symptoms (headache, mental slowness, incoordination) about 24–48 hours after the likely precipitant, which in each case was a single dose of a corticosteroid. In Patient 1, sleepiness at 48 hours progressed to incoherence, blurred vision, and severe agitation that required intubation 2 days later. In Patient 2, headache, nausea, blurred vision and epigastric pain at 48 hours progressed over the following 2 days to confusion and slow speech; by the following day, coma had developed, requiring intubation.

On their presentation to a peripheral hospital, an extensive panel of pathology investigations had been undertaken for each patient, including blood tests (full blood count, renal function tests, liver enzyme levels, coagulation profile and inflammatory markers), lumbar puncture and brain imaging (computed tomography and magnetic resonance imaging). The results of these investigations were all unremarkable.

Identification of significant hyperammonaemia was delayed…