Differential Diagnosis for Syncope and Vomiting with Viral Illness

Single Most Likely Diagnosis

• Vasovagal Syncope: This condition is characterized by a reflex of the involuntary nervous system that can cause a feeling of lightheadedness, sweating, nausea, and potentially fainting (syncope) in response to stressors such as pain, fear, or in this case, the physical stress of a viral illness. The vomiting could be a part of the vasovagal response or a consequence of the viral illness itself.

Other Likely Diagnoses

• Dehydration: Viral illnesses often lead to dehydration due to fever, sweating, and decreased fluid intake. Dehydration can cause symptoms of dizziness and fainting (syncope) and is commonly associated with vomiting.
• Postural Orthostatic Tachycardia Syndrome (POTS): This is a condition characterized by a rapid increase in heart rate and other symptoms that occur upon standing. It can be triggered or worsened by viral illnesses and may lead to syncope and vomiting due to inadequate blood flow to the brain.
• Gastroenteritis: While primarily causing gastrointestinal symptoms like vomiting and diarrhea, severe cases can lead to dehydration and electrolyte imbalances, potentially causing syncope.

Do Not Miss Diagnoses

• Cardiac Arrhythmias: Certain arrhythmias can cause syncope and may be triggered by the stress of a viral illness. Conditions like Long QT Syndrome are particularly dangerous and can be fatal if not recognized and treated.
• Myocarditis: Inflammation of the heart muscle, which can be caused by viral infections, leading to arrhythmias, heart failure, and potentially syncope.
• Pulmonary Embolism: Although less common, pulmonary embolism can present with syncope and vomiting, especially if there is associated hypoxia or a large clot burden.

Rare Diagnoses

• Mitochondrial Myopathies: Rare genetic disorders affecting the mitochondria, which can lead to a variety of systemic symptoms including those similar to viral illnesses, and potentially syncope and vomiting due to muscle weakness or metabolic derangements.
• Cyclic Vomiting Syndrome: A rare condition characterized by recurrent episodes of severe vomiting, which can be triggered by stress, including viral illnesses, and may lead to dehydration and syncope.
• Adrenal Insufficiency: A condition where the adrenal glands do not produce adequate amounts of hormones, potentially leading to hypotension, syncope, and gastrointestinal symptoms like vomiting, especially during times of stress such as viral illnesses.