New Diagnosis of Ornithine Transcarbamylase Deficiency in a 71-Year-Old Man

A 71-year-old male, diagnosed with a 2-month history of giant cell arteritis (GCA) (biopsy proven) and undergoing steroid therapy, presented to a community hospital with confusion, bilateral tremulousness, a wide-based gait and fatigue.Past medical history included GCA, dyslipidemia, cardiac septal thickening on echocardiogram with diastolic dysfunction, right retinal tear, bilateral cataract surgery and sudden left hearing loss of undetermined etiology (1 year ago).Comprehensive investigations, including complete blood count, liver and renal profiles, electrolytes, thyroid-stimulating hormone and cerebrospinal fluid cell count, protein and cultures, were normal.The only exception was elevated leukocytes (17.3 10*9/L), which was attributed to steroid use.A CT head with angiogram revealed no parenchymal abnormality or angiographic evidence of vasculopathy.He was discharged on day 3 of hospitalization after clinical stabilization.The differential diagnosis at that time included steroid-induced encephalopathy or possibly a GCA flare secondary to a recent reduction of the prednisone dose.Two weeks later, his condition worsened, prompting a return to the community hospital.A CT head and blood work, including a complete blood count, serum electrolytes, blood glucose, basic autoimmune profile and HIV serology, were normal.A venous blood gas showed evidence of respiratory alkalosis.Initially, he was disoriented but able to follow commands.However, the next day, he had an unwitnessed decline and was found with decreased responsiveness, was unable to follow commands and was not responding to pain with a Glasgow Coma Score of 4-5/15.A repeat non-contrast CT head was within normal limits for age.He was intubated for airway protection and transferred to the critical care unit at our tertiary care center.Upon reaching our center, he was not sedated and did not respond to voice or painful stimuli.Pupillary reactivity was intact, albeit with a right relative afferent pupillary defect.There was a weak