Differential Diagnosis for 64-year-old Female Patient

Single Most Likely Diagnosis

• Stroke (Ischemic or Hemorrhagic): Given the patient's history of hypertension, paroxysmal atrial fibrillation (not on anticoagulants), and symptoms of left-sided numbness in the face and leg, a stroke is the most likely diagnosis. The recent history of headache followed by focal neurological deficits further supports this diagnosis.

Other Likely Diagnoses

• Seizure: Although less likely, a seizure could present with focal neurological symptoms such as numbness. The history of headache could be a seizure aura, and the numbness could be a post-ictal phenomenon.
• Migraine with Aura: The patient's headache followed by neurological symptoms could be consistent with a migraine with aura, especially if the patient has a history of migraines.
• Transient Ischemic Attack (TIA): Given the transient nature of the symptoms (started today morning at 10 am), a TIA is also a possibility, although the duration and nature of the symptoms would need further clarification.

Do Not Miss Diagnoses

• Subarachnoid Hemorrhage: Although the CT scan results are not provided, it's crucial to consider subarachnoid hemorrhage due to the sudden onset of headache, which could be described as "thunderclap." Missing this diagnosis could be fatal.
• Cerebral Venous Thrombosis: Given the patient's history of chronic disease (SLE, RA, and recent IV iron infusion), there might be an increased risk of thrombotic events, including cerebral venous thrombosis.
• Intracranial Infection (e.g., Abscess): Although less likely, an intracranial infection could present with focal neurological deficits and headache, especially in the context of recurrent UTIs, which could be a source of bacteremia.

Rare Diagnoses

• Vasculitis (e.g., CNS Vasculitis): Given the patient's history of SLE and RA, vasculitis affecting the central nervous system is a rare but possible diagnosis that could explain the neurological symptoms.
• Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like episodes (MELAS): This is a rare mitochondrial disorder that can present with stroke-like episodes, but it would be unusual in a 64-year-old without a known history of the disease.
• CADASIL (Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy): A rare hereditary stroke disorder that could present with recurrent strokes and dementia, but it's less likely given the patient's age and lack of family history.