Differential Diagnosis

• Single most likely diagnosis
  • A Calciphylaxis: This is the most likely diagnosis given the patient's history of end-stage kidney disease, the presence of calcifications in the subcutaneous tissue, and the clinical presentation of an ulcerating, painful lesion. Calciphylaxis is a condition characterized by calcification of small and medium-sized blood vessels, often seen in patients with chronic kidney disease, particularly those on dialysis.
• Other Likely diagnoses
  • D Warfarin skin necrosis: Although the patient has been on warfarin for some time without recent changes, warfarin skin necrosis is a possibility, especially given the patient's elevated INR. However, the presence of calcifications and the specific histopathological findings make calciphylaxis more likely.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • B Leukocytoclastic vasculitis: This is an inflammatory condition that could present with skin lesions and should be considered due to its potential for systemic involvement and the need for prompt treatment. However, the histopathological findings do not strongly support this diagnosis.
  • C Venous stasis ulcer: While less likely given the acute onset and specific histological findings, venous stasis ulcers can be painful and should be considered, especially in patients with limited mobility or other risk factors for venous insufficiency.
• Rare diagnoses
  • Other rare conditions such as pancreatic panniculitis or traumatic panniculitis could be considered but are less likely given the clinical context and histopathological findings. These conditions would require specific additional findings or history that is not provided in the scenario.