Differential Diagnosis for Unconscious 14-year-old Child

Single most likely diagnosis

• Conversion Disorder: Given the patient's age, stable vitals, normal CBC, and reactive pupils, along with the absence of clear neurological deficits but presence of on and off stiffness and reactivity to pain, conversion disorder (a form of functional neurological symptom disorder) is a strong consideration. This condition is often triggered by psychological stress and can manifest as unexplained neurological symptoms, including altered mental status or loss of consciousness that cannot be explained by a medical condition.

Other Likely diagnoses

• Malingering: As you've suspected, malingering is a possibility, especially if there's a clear motive for the patient to feign illness. However, distinguishing between malingering and factitious disorder (or conversion disorder) can be challenging and requires careful observation and possibly psychiatric evaluation.
• Factitious Disorder: This condition, also known as Munchausen syndrome, involves the intentional production or feigning of physical or psychological symptoms, primarily driven by a psychological need to assume the sick role. It's a consideration, especially if there's evidence of fabrication or manipulation of symptoms.

Do Not Miss (ddxs that may not be likely, but would be deadly if missed)

• Non-convulsive Status Epilepticus: Although the patient is stable and has normal CBC, non-convulsive status epilepticus can present subtly, with altered mental status being a primary symptom. It's crucial to consider and rule out with EEG if there's any suspicion.
• Intracranial Hemorrhage or Mass: Even with stable vitals and normal initial labs, an intracranial hemorrhage or mass could present with altered mental status and should be considered, especially if there's any history of trauma or if the patient's condition worsens. Imaging studies (CT or MRI) would be necessary to rule this out.
• Infection (e.g., Meningitis, Encephalitis): Although the CBC is normal, infections like meningitis or encephalitis can present with altered mental status and should be considered, particularly if there are any signs of infection or if the patient's condition deteriorates.

Rare diagnoses

• Mitochondrial Disorders: Certain mitochondrial disorders can present with episodes of altered mental status, among other symptoms. These are rare genetic disorders affecting the mitochondria.
• Hashimoto's Encephalopathy: A rare condition associated with Hashimoto's thyroiditis, characterized by altered mental status, seizures, and stroke-like symptoms, which improves with corticosteroid treatment.
• Acute Demyelinating Encephalomyelitis (ADEM): A rare autoimmune disease characterized by a sudden, widespread attack of inflammation in the brain and spinal cord, which can present with altered mental status, among other neurological symptoms.

Each of these diagnoses requires careful consideration of the patient's history, physical examination, and additional diagnostic tests to determine the underlying cause of the altered mental status.