Differential Diagnosis for Unilateral Purpura
Single Most Likely Diagnosis
- Henoch-Schönlein Purpura (HSP): This condition is a form of vasculitis that affects small blood vessels and is characterized by the deposition of IgA immune complexes. It often presents with unilateral purpura, particularly on the lower extremities, and can be accompanied by abdominal pain, arthritis, and renal involvement. The unilateral nature of the purpura, along with the potential for other systemic symptoms, makes HSP a leading consideration.
Other Likely Diagnoses
- Trauma: Direct injury to a limb can cause unilateral purpura due to blood leakage from damaged vessels into the skin. The history of trauma and the location of the purpura can help differentiate this from other causes.
- Infection (e.g., cellulitis, necrotizing fasciitis): Certain infections can cause purpura, especially if they involve the skin and soft tissues. These conditions often present with additional symptoms such as redness, swelling, warmth, and sometimes fever.
- Thrombocytopenia or coagulopathy: Conditions that affect platelet count or function, or the coagulation cascade, can lead to purpura. However, these conditions typically cause more widespread symptoms rather than unilateral purpura.
Do Not Miss Diagnoses
- Meningococcemia: This is a severe infection caused by Neisseria meningitidis, which can present with purpura as part of its initial symptoms. It is critical to identify and treat promptly due to its high mortality rate if left untreated.
- Septic emboli: Infections that lead to septic emboli, such as endocarditis, can cause unilateral purpura among other symptoms. Early diagnosis is crucial for effective management.
- Vasculitis (other forms): While HSP is a common form of vasculitis, other types like granulomatosis with polyangiitis (formerly known as Wegener's granulomatosis) or microscopic polyangiitis can also present with purpura and require prompt treatment to prevent serious complications.
Rare Diagnoses
- Ehlers-Danlos syndrome: A group of disorders that affect connective tissues supporting the skin, bones, blood vessels, and many other organs and tissues. Some types can lead to easy bruising and purpura.
- Fabry disease: A genetic disorder that results from the buildup of a particular type of fat in the body's cells, which can cause purpura among a wide range of other symptoms.
- Amyloidosis: A condition characterized by the deposition of amyloid (a particular type of protein) in various tissues of the body, which can lead to purpura, particularly when associated with bleeding or coagulation disorders.