Differential Diagnosis for Multiple Syncope with Erythema Rubrum (Eternal Rub)

Single Most Likely Diagnosis

• Vasovagal Syncope with Erythema: This condition is characterized by fainting spells that can occur in succession, often triggered by stress, pain, or prolonged standing. The erythema (redness of the skin) could be a manifestation of the body's response to the stress of repeated syncope, possibly due to increased blood flow or an allergic reaction to the repeated stress on the body.

Other Likely Diagnoses

• Orthostatic Hypotension: This condition involves a sudden drop in blood pressure upon standing, which can lead to syncope. Repeated episodes could occur if the individual quickly stands up after recovering from a faint, not giving their body enough time to adjust.
• Cardiac Arrhythmias: Certain arrhythmias, such as supraventricular tachycardia (SVT) or ventricular tachycardia, can cause syncope. The erythema could be unrelated or a sign of another condition but is noted here as the patient wakes up with it.
• Seizure Disorders: Although less common, certain seizure types can present with loss of consciousness that might be mistaken for syncope, followed by a post-ictal phase where the patient could exhibit erythema due to increased body temperature or physical exertion during the seizure.

Do Not Miss Diagnoses

• Cardiac Tamponade: A life-threatening condition where fluid accumulates in the sac around the heart, impeding its ability to pump blood effectively. Syncope can occur due to reduced cardiac output, and while erythema is not a direct symptom, it's crucial to consider this diagnosis due to its high mortality rate if untreated.
• Pulmonary Embolism: A blockage of an artery in the lungs, which can cause syncope among other symptoms like shortness of breath and chest pain. Erythema might not be directly related but could be part of a broader clinical picture.
• Aortic Dissection: A serious condition where there is a tear in the aorta's inner layer. Syncope can occur due to severe pain or reduced blood flow to the brain. While erythema is not a typical symptom, missing this diagnosis can be fatal.

Rare Diagnoses

• Malignant Neuroleptic Syndrome: A rare but life-threatening neurological disorder caused by an adverse reaction to neuroleptic or antipsychotic medication. Symptoms can include fever, confusion, and changes in mental status, which might be accompanied by erythema.
• Pheochromocytoma: A rare tumor of the adrenal gland that can cause episodes of high blood pressure, leading to syncope. Erythema could be part of the flushing that some patients experience due to the catecholamine surge.

Each of these diagnoses requires careful consideration of the patient's full clinical picture, including history, physical examination, and diagnostic tests to determine the underlying cause of the symptoms.