Differential Diagnosis
The patient's complex presentation of cognitive decline, psychiatric symptoms, and systemic findings requires a thorough evaluation of various potential causes. The following differential diagnosis is organized into categories to facilitate consideration of the most likely and critical diagnoses.
- Single most likely diagnosis
- Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME): The patient's history of severe respiratory illness, followed by persistent cognitive issues, increased sleep needs, and significant fatigue, is consistent with CFS/ME. The fluctuating course, with periods of improvement and worsening, also supports this diagnosis.
- Other Likely diagnoses
- Post-Infectious Encephalitis: The patient's severe respiratory illness and subsequent cognitive decline suggest a possible post-infectious encephalitis, although the lack of identified antibodies and normal CSF findings make this less likely.
- Sleep Disorder: The patient's sleep study results and prescribed mouthguard device suggest a sleep disorder, such as sleep apnea or bruxism, which could contribute to cognitive issues and fatigue.
- Depression with Cognitive Impairment: The patient's history of depression and suicidal ideation, combined with cognitive symptoms, could indicate a depressive disorder with cognitive impairment.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Lymphoma: The patient's right ileocolic lymphadenopathy and clustered nodes on CT scan, although PET scan-negative for cancer, warrant consideration of lymphoma, which could cause cognitive and systemic symptoms.
- Neurosyphilis: This condition can cause cognitive decline, psychiatric symptoms, and systemic findings, and is essential to rule out due to its treatable nature.
- Vitamin B12 Deficiency: A deficiency in vitamin B12 can cause cognitive impairment, fatigue, and psychiatric symptoms, and is crucial to diagnose and treat to prevent long-term damage.
- Rare diagnoses
- Hashimoto's Encephalopathy: This rare condition, associated with Hashimoto's thyroiditis, can cause cognitive decline, psychiatric symptoms, and systemic findings, and is essential to consider in the differential diagnosis.
- Prion Disease: Although extremely rare, prion diseases like Creutzfeldt-Jakob disease can cause rapid cognitive decline, psychiatric symptoms, and systemic findings, and should be considered in the differential diagnosis.
Treatment for the patient's condition will depend on the underlying cause. If CFS/ME is confirmed, treatment may involve a multidisciplinary approach, including cognitive behavioral therapy, sleep management, and medication to manage symptoms. If another diagnosis is established, treatment will be tailored to address the specific condition. Further evaluation and testing may be necessary to determine the underlying cause of the patient's symptoms.