Differential Diagnosis for Unexplained Bruising

The patient's presentation of a growing, emerging bruise on the shoulder without a history of impact, combined with chronic infections, autoimmune issues, and a connective tissue disorder, suggests a complex underlying condition. The differential diagnosis can be categorized as follows:

• Single Most Likely Diagnosis

  • Vasculitis: Given the patient's history of autoimmune issues and connective tissue disorder, vasculitis is a plausible cause. Vasculitis can lead to inflammation of blood vessels, making them more susceptible to bruising and bleeding. The absence of a traumatic history and the presence of systemic symptoms such as chronic infections support this diagnosis.

• Other Likely Diagnoses

  • Immunothrombocytopenic Purpura (ITP): This condition, characterized by low platelet count due to immune system dysfunction, could explain the bruising. The patient's autoimmune issues make ITP a consideration.
  • Antiphospholipid Syndrome (APS): APS is an autoimmune disorder that can cause blood clots and bruising. Given the patient's history of autoimmune issues, APS is a potential cause.
  • Ehlers-Danlos Syndrome (EDS): As a connective tissue disorder, EDS can lead to fragile blood vessels and easy bruising. The patient's existing connective tissue disorder diagnosis makes EDS a possible contributor to the bruising.

• Do Not Miss Diagnoses

  • Malignancy: Certain cancers, such as leukemia or lymphoma, can cause bruising due to bone marrow suppression or platelet dysfunction. Although less likely, missing a diagnosis of malignancy could be devastating.
  • Scurvy: Vitamin C deficiency can lead to connective tissue weakness, resulting in easy bruising. Given the patient's chronic infections and potential for malabsorption or poor nutrition, scurvy is a critical diagnosis not to miss.
  • Amyloidosis: This condition involves the deposition of abnormal proteins in tissues, which can affect blood vessels and lead to bruising. Amyloidosis can be associated with chronic infections and autoimmune diseases, making it a crucial diagnosis to consider.

• Rare Diagnoses

  • Pseudoxanthoma Elasticum (PXE): A genetic disorder affecting connective tissue, PXE can lead to elastic fiber mineralization and fragmentation, potentially causing easy bruising.
  • Sickle Cell Disease: Although less common in a 45-year-old without a known history, sickle cell disease can cause vascular complications, including bruising, especially if the patient has a previously undiagnosed or variant form of the disease.