Interferon-alpha induced ‘tertiary mania’

Abstract

A 32-year-old woman with no previous history of psychiatric illness was admitted to an acute psychiatric unit, having been behaving increasingly bizarrely over the previous week. She had persecutory delusions and grandiosity, but admitted to a 2-week history of low mood. Her sleep was disturbed and she had not slept at all on the night before admission. At admission she fluctuated between elation and aggression. Her speech was pressured and she demonstrated flight of ideas as well as poor attention and marked distractability. She had been treated for the previous 4 years with recombinant interferon-alpha by subcutaneous injection for essential thrombocythaemia, her dose having been gradually reduced to 3 megaunits twice-weekly at the time of admission. Physical examination on admission revealed no abnormalities. However, routine biochemical investigation revealed her to be profoundly hypothyroid, with a free thyroxine of 1 pmol/litre (10–26) and a thyroid- stimulating hormone of >84 mU/litre (0.5–6.5). Further investigation revealed a raised thyroid microsome antibody at 6400 units (<400). Her platelet count was 435×109/litre, revealing her essential thrombocythaemia to be well controlled. All other investigations, including electrocardiogram, lipids, creatinine kinase and lactate dehydrogenase, were normal. The patient required restraint and sedation. Her mental state improved rapidly over the following few days on oral haloperidol 5 mg three times daily. On discovery of her hypothyroidism, she denied a history of any classical physical symptoms. She was commenced on thyroxine 50 μg daily and her interferon-alpha discontinued. Her haloperidol was reduced and then discontinued at 1 month post-discharge. She has since remained well during the subsequent 12 months.