(1020) Defying Diagnostic Odds: Diagnosing Neuroleptic Malignant Syndrome (NMS) Amidst Confounders

Introduction: Typically caused by dopaminergic antagonism from antipsychotics or neuroleptics, NMS results in dysautonomia with associated laboratory abnormalities. In patients with pre-existing confounders, as in this patient with Lesch-Nyhan syndrome (LNS), NMS may present as a diagnostic conundrum.

Description: A 27 year-old-male with LNS, dysautonomia, renal tubular acidosis, and recurrent hospitalizations for urinary tract infections and gastrostomy-jejunostomy (GJ) tube malfunction was admitted with metabolic derangements and GJ-tube malfunction requiring an exchange. On day 3 post-exchange, he developed hypotension and fever, triggering a sepsis alert, which then prompted fluids, antibiotics, and an ICU transfer. On day 4, he was persistently diaphoretic, dyspneic, febrile (103 F), and hypertensive. His exam showed upper and lower extremity rigidity without meningism, clonus, catatonia, or hyperreflexia. Labs showed hypernatremia, transaminitis, and leukocytosis. Cultures and pan-CT were negative for infection. A worsening mixed anion and non-gap metabolic acidosis from his baseline prompted checking for a lactate and CPK, which were normal and elevated (9K), respectively. This led to a medication review confirming he had received 1500mg of his home dose of quetiapine, haloperidol 10mg, and olanzapine 10mg over the past 3 days for agitation. Due to an unrevealing infectious work up with data suggestive of NMS, psychiatry was consulted and all antipsychotics were discontinued. While managing his dehydration and fevers, he was started on lorazepam and bromocriptine. Thereafter, his mental status, dysautonomia, fevers, dehydration, and laboratory abnormalities gradually improved. He was then continued on bromocriptine which was tapered off after 3 weeks. Due to his ongoing agitation, he was eventually re-challenged slowly with quetiapine 2 weeks after symptom resolution and discharged home with psychiatry follow-up.

Discussion: Despite pre-existing confounders such as dysautonomia, metabolic derangements, and recurrent infections in this patient with LNS who developed NMS, our knowledge of major and essential diagnostic criteria for NMS, pharmacovigilance, and high clinical index of suspicion were key in the timely diagnosis and management of this uncommon yet fatal syndrome.