What syndrome is characterized by symptoms such as agitation, muscle rigidity, and myoclonus?

Neuroleptic Malignant Syndrome (NMS) is characterized by a triad of symptoms including severe muscle rigidity, high fever, altered mental status, and autonomic dysfunction. Among the symptoms presented in the question—agitation, muscle rigidity, and myoclonus—muscle rigidity is a definitive feature of NMS, which generally presents after the administration of antipsychotic medications.

Agitation may also be seen in NMS as the altered mental status can lead to restlessness. Myoclonus, while not the primary feature of NMS, may still occur as a part of the neurological manifestations associated with severe rigidity and altered responsiveness. Recognizing NMS is critical as it requires immediate medical attention due to its potentially life-threatening complications.

In contrast, while Serotonin Syndrome can also present with agitation and hyperreflexia (which could be confused with myoclonus), it is more commonly associated with other symptoms such as gastrointestinal distress and mydriasis. Ethanol Withdrawal Syndrome primarily presents with symptoms like tremors, anxiety, and seizures, rather than muscle rigidity. Substance Induced Psychotic Disorder involves primarily severe alterations in thought processes and perception rather than the specific physical symptoms noted.