Differential Diagnosis

The patient's presentation is complex, given her past medical history and recent concussion. The following differential diagnoses are considered:

• Single Most Likely Diagnosis

  • Postural Orthostatic Tachycardia Syndrome (POTS): This condition is characterized by a rapid increase in heart rate and other symptoms that occur upon standing. Given the patient's recent history of concussion and symptoms of tachycardia when standing, POTS is a plausible diagnosis. The mechanical fall and concussion could have triggered or exacerbated POTS symptoms.

• Other Likely Diagnoses

  • Autonomic Dysfunction: This could be related to her known cerebral telangiectasia or a consequence of the recent concussion, affecting autonomic nervous system function and leading to orthostasis and tachycardia.
  • Hypothyroidism exacerbation: Although she has a history of hypothyroidism, if her condition is not well-managed, it could contribute to her symptoms, including orthostasis and tachycardia.
  • Systemic Lupus Erythematosus (SLE) or Antiphospholipid Syndrome (APLS) flare: Given her query diagnosis of APLS vs SLE, a flare of either condition could explain her symptoms, including orthostasis and pain behind one eye, potentially due to vasculitis or thrombotic events.

• Do Not Miss Diagnoses

  • Subarachnoid Hemorrhage or other intracranial hemorrhage: Although she had a concussion, any worsening or new symptoms, especially pain behind one eye, necessitate ruling out a more severe intracranial hemorrhage, particularly given her history of brain cavernous malformations.
  • Pulmonary Embolism: This is a critical diagnosis to consider, especially in patients with a history suggestive of APLS, as it can cause tachycardia and orthostatic symptoms.
  • Cardiac causes of tachycardia and orthostasis: Conditions such as cardiac tamponade or severe cardiac dysfunction need to be ruled out, as they can present with similar symptoms.

• Rare Diagnoses

  • Multiple System Atrophy (MSA): A rare neurodegenerative disorder that can cause autonomic dysfunction leading to orthostatic hypotension and tachycardia.
  • Pheochromocytoma: A rare tumor of the adrenal gland that can cause episodes of tachycardia, hypertension, and orthostatic hypotension.
  • Ehlers-Danlos Syndrome: A group of disorders that affect connective tissues supporting the skin, bones, blood vessels, and many other organs and tissues, which could potentially explain some of her symptoms, including orthostasis and possibly the cerebral vascular malformations.