Differential Diagnosis for a 53-year-old Male with IgG-4 Disease and Persistent Leg Swelling

Single Most Likely Diagnosis

• Cellulitis or persistent infection: Given the patient's history of injury, swelling, and redness, a persistent or unresolved infection is a plausible explanation. The patient's IgG-4 disease might complicate the clinical picture but doesn't directly point to an alternative diagnosis without more specific symptoms.

Other Likely Diagnoses

• Deep Vein Thrombosis (DVT): The swelling and history of recent injury could predispose to DVT, especially if the patient has been less mobile due to pain or discomfort from the injury.
• Lymphedema: Although less common, if the injury affected lymphatic vessels, it could lead to lymphedema, which would cause persistent swelling.
• IgG-4 Related Disease flare: While IgG-4 disease primarily affects organs like the pancreas, biliary tree, and salivary glands, it can also involve other tissues. A flare of the disease could potentially cause swelling in the affected limb, though this would be less common.

Do Not Miss Diagnoses

• Compartment Syndrome: Although the timeline might be a bit long for acute compartment syndrome, if the patient has been experiencing increasing pain, especially on passive stretching of the muscles within the compartment, this diagnosis must be considered due to its potential for severe and irreversible damage.
• Osteomyelitis: A bone infection could develop after an injury, especially if the wound became infected. This condition requires prompt diagnosis and treatment to prevent long-term damage.
• Malignancy (e.g., soft tissue sarcoma): While rare, any unexplained and persistent swelling should prompt consideration of malignancy, especially in adults.

Rare Diagnoses

• Erythema nodosum: An inflammatory condition characterized by nodular skin lesions, typically on the lower legs, which could be a manifestation of an underlying disease, including infections, autoimmune disorders, or reactions to medications.
• Sarcoidosis: A condition that can cause inflammation in various parts of the body, including the skin, and could potentially cause leg swelling, though it would be an unusual presentation.
• Lipedema: A chronic condition characterized by the abnormal growth of fat cells in the legs, leading to swelling, though it typically presents bilaterally and without a clear inciting injury.