Differential Diagnosis for Acute Onset of Severe Pain in the Palm with Purple Spots
Single Most Likely Diagnosis
- Postherpetic Neuralgia with Associated Vasculitis: Given the patient's history of shingles three weeks ago, postherpetic neuralgia (PHN) is a common complication that can cause severe pain. The presence of purple spots could indicate a vasculitic reaction, which, although less common, can be associated with herpes zoster infections.
Other Likely Diagnoses
- Herpes Zoster Infection with Superinfection: The patient's recent history of shingles increases the risk of superinfection, which could cause severe pain and skin lesions, including purple spots due to bacterial or fungal infections.
- Vasculitis (e.g., Giant Cell Arteritis, Polyarteritis Nodosa): Vasculitis can cause skin lesions and pain, and while less common, it should be considered, especially in an elderly patient with acute onset of symptoms.
- Thrombocytopenia or Coagulopathy: Conditions affecting blood clotting could lead to purpura (purple spots) and potentially severe pain if there's associated bleeding or thrombosis.
Do Not Miss Diagnoses
- Septic Arthritis or Osteomyelitis: Infections in the joints or bones can cause severe pain and could be life-threatening if not promptly treated. The presence of purple spots could indicate a spreading infection.
- Endocarditis: Although less directly related to the symptoms, endocarditis can cause embolic phenomena leading to skin lesions and severe pain, and is critical not to miss due to its high mortality rate.
- Disseminated Intravascular Coagulation (DIC): A condition that can cause both severe pain and purpura, DIC is life-threatening and requires immediate diagnosis and treatment.
Rare Diagnoses
- Leukocytoclastic Vasculitis: A rare condition characterized by inflammation of the blood vessels, which could explain the purple spots and pain.
- Cholesterol Crystal Embolization: A rare condition where cholesterol crystals embolize and cause inflammation and pain in the affected area, potentially causing skin lesions.
- Sweets Syndrome: A rare condition characterized by fever, leukocytosis, and tender, erythematous, well-demarcated papules and plaques, which could be considered in the differential diagnosis of a patient with severe pain and skin lesions.