Differential Diagnosis for a 5-year-old Girl with Lethargy and Altered Mental Status
- Single most likely diagnosis:
- Reye's syndrome: This condition is characterized by acute non-inflammatory encephalopathy and fatty degenerative liver disease, typically occurring after a viral infection, especially influenza or varicella, and often associated with the use of aspirin. The patient's presentation of fever, malaise, headache, cough, and nasal discharge followed by nausea, vomiting, lethargy, and hepatomegaly, along with diffuse cerebral edema on CT scan, is highly suggestive of Reye's syndrome.
- Other Likely diagnoses:
- Viral encephalitis: Given the patient's initial symptoms of fever, headache, and cough, which are common in viral infections, and the progression to altered mental status and cerebral edema, viral encephalitis is a plausible diagnosis. Viruses such as herpes simplex, enteroviruses, and arboviruses can cause encephalitis.
- Bacterial meningitis: Although the patient's fever resolved initially, bacterial meningitis can present with lethargy, altered mental status, and signs of increased intracranial pressure. The absence of neck stiffness and the presence of hepatomegaly make this less likely but still a consideration.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed):
- Intracranial hemorrhage or stroke: These conditions can present with sudden onset of lethargy and altered mental status. Although less common in children, they are critical to diagnose promptly due to their high morbidity and mortality.
- Brain tumor: Although rare and less likely given the acute presentation, a brain tumor could cause increased intracranial pressure and altered mental status. It's essential to consider this diagnosis to avoid missing a potentially treatable condition.
- Toxic ingestion: Accidental ingestion of toxins or medications can lead to altered mental status and should be considered, especially in a child who has been vomiting and is lethargic.
- Rare diagnoses:
- Mitochondrial disorders: These are a group of disorders caused by dysfunctional mitochondria, affecting multiple organ systems. Some mitochondrial disorders can present with episodes of metabolic crisis, including encephalopathy and liver dysfunction, similar to what is seen in Reye's syndrome.
- Acute disseminated encephalomyelitis (ADEM): ADEM is a rare autoimmune disease characterized by a monophasic illness with multifocal neurological deficits, often following a viral infection or vaccination. It could be considered in the differential diagnosis due to the patient's encephalopathy and recent viral illness.