Differential Diagnosis for the Patient's Condition

The patient presents with a complex set of symptoms including psychosis, stupor, diaphoresis, high fever, tachycardia, symmetric rigidity of extremities, decreased reflexes, and normal extremity diameter. Given the medication regimen that includes risperidone, Reglan (metoclopramide), benztropine, and hydroxyzine, several potential diagnoses must be considered.

• Single Most Likely Diagnosis

  • Neuroleptic Malignant Syndrome (NMS): This is a life-threatening, neurological disorder most often caused by an adverse reaction to neuroleptic or antipsychotic medication. The patient's symptoms of high fever, rigidity, altered mental status (stupor), and autonomic dysfunction (diaphoresis, tachycardia) are classic for NMS. The use of risperidone, a potent antipsychotic, increases the risk for this condition.

• Other Likely Diagnoses

  • Serotonin Syndrome: Although less likely given the specific medication regimen, serotonin syndrome is a possibility, especially if there are any serotonergic medications being used concurrently (not explicitly mentioned but possible with other medications). Symptoms can overlap with NMS, including altered mental status, rigidity, and autonomic instability.
  • Malignant Hyperthermia: This is a rare but life-threatening medical emergency triggered by certain medications used for general anesthesia, not directly implicated by the patient's current medication list but could be considered if there were recent surgical procedures.
  • Parkinsonian Hyperpyrexia Syndrome: A rare condition associated with the abrupt withdrawal of dopaminergic medications or the use of antipsychotics in patients with Parkinson's disease. The patient's use of benztropine (an anticholinergic) and the presence of rigidity might suggest this, but it's less likely without a known history of Parkinson's disease.

• Do Not Miss Diagnoses

  • Infection (e.g., Sepsis): High fever and altered mental status could indicate a severe infection. It's crucial to rule out sepsis or other infections, as they require immediate antibiotic treatment.
  • Heat Stroke: Especially if the patient has been exposed to high temperatures or has been physically active, heat stroke could present with similar symptoms, including high fever, altered mental status, and rigidity.
  • Central Nervous System (CNS) Infection: Conditions like meningitis or encephalitis could present with fever, altered mental status, and rigidity, making them critical to rule out.

• Rare Diagnoses

  • Dystonic Storm: A rare condition characterized by intense, frequent episodes of dystonia, which could potentially present with rigidity and altered mental status, especially in the context of antipsychotic and anticholinergic use.
  • Lethal Catatonia: A rare condition that can present with immobility, rigidity, and altered mental status, often accompanied by fever and autonomic instability. It can be difficult to distinguish from NMS without a clear history of catatonia.

Each of these diagnoses requires careful consideration, and immediate action should be taken to address the most life-threatening conditions, particularly NMS and infections.