Differential Diagnosis

The patient presents with symptoms of shortness of breath, inability to lay flat (orthopnea), dyspnea on exertion, and spontaneous lightheadedness whilst sitting, alongside a complex medical history including coronary artery disease (CAD) with a history of coronary artery bypass grafting (CABG) 15 years ago, interstitial lung disease, chronic kidney disease (CKD) stage 3, rapidly progressive glomerulonephritis (RPGN), and a recent diagnosis of melanoma of the right lower extremity (RLE) stage IIID with no residual disease after starting adjuvant treatment with nivolumab.

• Single Most Likely Diagnosis:

  • Heart Failure (HF): Given the patient's history of CAD and CABG, along with symptoms of orthopnea and dyspnea on exertion, heart failure is a highly plausible diagnosis. The recent onset of symptoms could be related to a decline in cardiac function, possibly exacerbated by the patient's other medical conditions.

• Other Likely Diagnoses:

  • Pulmonary Embolism (PE): Although less likely than heart failure given the symptom profile, PE is a consideration, especially in a patient with a recent cancer diagnosis and possible immobility, which increases the risk of venous thromboembolism.
  • Anemia or Electrolyte Imbalance: Given the patient's CKD stage 3 and RPGN, anemia or electrolyte imbalances (e.g., hyperkalemia) could contribute to the symptoms of shortness of breath and lightheadedness.
  • Fluid Overload: Related to CKD and possibly exacerbated by heart failure, fluid overload could explain the shortness of breath and orthopnea.

• Do Not Miss Diagnoses:

  • Pulmonary Hypertension: This condition can cause dyspnea and is particularly concerning in patients with interstitial lung disease. It would be critical to diagnose due to its significant impact on prognosis and management.
  • Cardiac Tamponade: Although less common, cardiac tamponade can cause sudden onset of shortness of breath and lightheadedness. Given the patient's history of CABG and recent initiation of immunotherapy, which can have cardiac side effects, this diagnosis must be considered.
  • Sepsis: Infection can lead to sepsis, which might present with non-specific symptoms including shortness of breath and lightheadedness, especially in a patient with a compromised immune system due to cancer and immunotherapy.

• Rare Diagnoses:

  • Nivolumab-induced Myocarditis or Pneumonitis: While rare, immunotherapy with nivolumab can cause myocarditis or pneumonitis, which could explain the patient's symptoms. Given the recent start of adjuvant treatment, this is a rare but important consideration.
  • Thrombotic Microangiopathy (TMA): A rare condition that could be related to the patient's RPGN and CKD, TMA might cause symptoms due to microvascular thrombi formation affecting various organs, including the lungs and heart.