Differential Diagnosis for Painful Rash to Face, Headache, and Pain Going Down Face

• Single Most Likely Diagnosis
  • Herpes Zoster (Shingles): This is the most likely diagnosis given the symptoms of a painful rash on the face, headache, and pain radiating down the face. The pain and rash are typically unilateral and follow a dermatomal distribution, which is consistent with the description.
• Other Likely Diagnoses
  • Trigeminal Neuralgia: This condition involves sudden, severe, and shock-like pain around the eyes, lips, or nose mainly because of abnormal blood vessels pressing on the trigeminal nerve in the head. While it doesn't typically cause a rash, the pain description could fit, especially if the rash is not the primary concern.
  • Temporal Arteritis (Giant Cell Arteritis): This condition can cause headaches and facial pain, especially in older adults. While a rash is not a primary symptom, the condition can lead to visual disturbances and jaw claudication, making it a consideration in the differential diagnosis.
• Do Not Miss Diagnoses
  • Lyme Disease: Early stages of Lyme disease can present with a distinctive rash (erythema migrans) and neurological symptoms, including headaches and facial pain. Given its potential for serious complications if untreated, it's crucial not to miss this diagnosis.
  • Ramsay Hunt Syndrome Type 2: This condition, caused by the varicella-zoster virus, can lead to facial paralysis, ear pain, and a rash in the ear or mouth. It's a serious condition that requires prompt treatment to prevent long-term sequelae.
  • Cavernous Sinus Thrombosis: Although rare, this condition is life-threatening and can present with facial pain, headache, and possibly a rash if there's an associated infection or inflammation. It's essential to consider this in the differential due to its high mortality rate if not promptly treated.
• Rare Diagnoses
  • Sjögren's Syndrome: An autoimmune disorder that can cause facial pain, headaches, and possibly a rash, though it's more commonly associated with dry eyes and mouth.
  • Erythromelalgia: A disorder characterized by burning pain, heat, and redness in the hands and feet but can occasionally affect the face, presenting with a rash-like appearance due to the intense redness and heat.