Differential Diagnosis

• Single most likely diagnosis
  • Lymphoma: The patient's symptoms of weight loss, lymphadenopathy in abdominal and mediastinal areas, and a history of a recent procedure (ERCP) could suggest a malignancy such as lymphoma. The presence of baseline interstitial lung disease (ILD) with a nonspecific interstitial pneumonia (NSIP) pattern may also be related to lymphoma.
• Other Likely diagnoses
  • Metastatic cancer: Given the patient's history of a common bile duct (CBD) stone and ERCP, there could be a possibility of a primary malignancy (e.g., cholangiocarcinoma, pancreatic cancer) that has metastasized to lymph nodes.
  • Sarcoidosis: This condition can cause lymphadenopathy, ILD, and systemic symptoms like weight loss. It might also explain the patient's baseline ILD/NSIP.
  • Infection (e.g., tuberculosis, fungal infections): These can cause lymphadenopathy, weight loss, and systemic symptoms, especially in an elderly patient with potential immune compromise.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Lymphoproliferative disorder post-ERCP: Although rare, ERCP has been associated with lymphoproliferative disorders in some cases.
  • Castleman disease: A rare disorder that can cause lymphadenopathy, systemic symptoms, and ILD.
  • Autoimmune lymphoproliferative syndrome (ALPS): A rare condition that could explain lymphadenopathy and systemic symptoms.
• Rare diagnoses
  • Idiopathic multicentric Castleman disease: A rare condition characterized by lymphadenopathy, systemic symptoms, and sometimes ILD.
  • Kikuchi-Fujimoto disease: A rare, self-limiting condition that causes lymphadenopathy, usually in the neck, but can be systemic.
  • Kimura disease: A rare, chronic inflammatory disorder that can cause lymphadenopathy and eosinophilia.

Justification

The patient's complex presentation with weight loss, lymphadenopathy, and a history of recent ERCP and CBD stone removal suggests a malignancy or a systemic disease process. The presence of baseline ILD/NSIP adds another layer of complexity, suggesting an autoimmune or inflammatory component. The differential diagnoses are broad, reflecting the wide range of possible causes for these symptoms. However, lymphoma stands out as a single most likely diagnosis due to its ability to explain most of the patient's symptoms and findings.