Neuroleptic Malignant Syndrome (NMS) is a rare, life-threatening complication of antipsychotic medication. There are no gold standard tests to diagnose NMS, however various diagnostic criteria have been suggested. NMS is typically reported in patients who have recently commenced an antipsychotic or had a change in dose. This case report describes an elderly female who developed NMS after being treated with the same dose of antipsychotic for 7 years. We aimed to establish whether similar cases are commonly reported, and what the key learning outcomes are.

This case presents an 82-year-old female taking the same dose of zuclopenthixol for 7 years. She was admitted with increased confusion and was initially prescribed antibiotics for a possible infection. She later became pyrexial and developed hypertonia, at which point NMS was suspected. Her creatinine kinase titre was significantly elevated, and her antipsychotic was discontinued. A potential trigger was a significant rectal bleed occurring a few weeks prior with no other obvious triggers noted. She was switched to quetiapine but developed NMS again when this dose was increased.

There are few reports of NMS occurring in patients taking a long-term and stable antipsychotic dose. One case describes NMS developing after 30 years on Clozapine with no clear trigger. Another reports NMS after 7 years on Olanzapine, however this was triggered by dehydration. This case is an example of NMS in an elderly patient with a complex medical history who was initially misdiagnosed with sepsis before NMS was suspected. This shows the importance of considering NMS not only in those who have recently commenced antipsychotics or recently changed dose, but also those who have been stable on medication for a number of years. In suspected NMS, we should aim to stop relevant medication immediately and commence conservative management. It is important to highlight these atypical presentations so that NMS can be recognised without delaying treatment, thereby reducing mortality and improving patient outcomes

This report highlights the importance of considering NMS in patients who have been prescribed the same dose of antipsychotic for an extended period. Awareness of potential risk factors such as medical comorbidity that may trigger an episode of NMS even in those on established antipsychotic treatment is vital. Symptoms may mimic infection and it is important to raise awareness of atypical presentations to effectively identify, and treat, NMS earlier to improve outcomes.