Differential Diagnosis for Vasculitis with Purpura, Petechiae, Maculopapular Rash on Lower Extremities
Single Most Likely Diagnosis
- Henoch-Schönlein Purpura (HSP): This condition is characterized by the deposition of IgA immune complexes, leading to vasculitis. It typically presents with purpura, abdominal pain, arthralgias, and renal involvement. The presence of purpura and maculopapular rash on the lower extremities, especially in children and young adults, makes HSP a leading consideration.
Other Likely Diagnoses
- Leukocytoclastic Vasculitis: This is a form of small vessel vasculitis that can present with similar skin manifestations, including purpura and petechiae. It can be associated with infections, medications, or systemic diseases.
- Systemic Lupus Erythematosus (SLE): SLE can cause a wide range of skin manifestations, including vasculitis, which may present as purpura or petechiae. The presence of other systemic symptoms such as joint pain, renal issues, or typical lupus rashes would support this diagnosis.
- Rheumatoid Vasculitis: Although less common, rheumatoid arthritis can lead to vasculitis, particularly in patients with long-standing, severe disease. This would typically be accompanied by other symptoms of rheumatoid arthritis.
Do Not Miss Diagnoses
- Meningococcemia: This is a life-threatening condition caused by Neisseria meningitidis. It can present with a rapidly progressive petechial or purpuric rash, often accompanied by fever and signs of sepsis. Early recognition and treatment are crucial.
- Thrombotic Thrombocytopenic Purpura (TTP): TTP is characterized by thrombocytopenia, microangiopathic hemolytic anemia, renal failure, neurological symptoms, and fever. The presence of purpura or petechiae could be part of the presentation, and it requires immediate attention due to its high mortality rate if untreated.
- Disseminated Intravascular Coagulation (DIC): DIC can cause a variety of skin manifestations, including purpura and petechiae, due to the consumption of clotting factors and platelets. It is often associated with severe underlying conditions such as sepsis, trauma, or malignancy.
Rare Diagnoses
- Granulomatosis with Polyangiitis (GPA, formerly known as Wegener's Granulomatosis): This is a form of vasculitis that primarily affects small to medium-sized vessels and is associated with granulomatous inflammation of the respiratory tract and necrotizing vasculitis of small and medium-sized vessels. Skin manifestations can include purpura and petechiae, but they are less common than respiratory and renal symptoms.
- Eosinophilic Granulomatosis with Polyangiitis (EGPA, formerly known as Churg-Strauss Syndrome): This condition is characterized by asthma, eosinophilia, and vasculitis affecting multiple organ systems. Skin manifestations can include purpura, but the diagnosis is typically made in the context of a patient with a history of asthma and significant eosinophilia.
- Cryoglobulinemic Vasculitis: This is a rare condition caused by the deposition of cryoglobulins (proteins that precipitate from blood at cold temperatures) in blood vessel walls, leading to vasculitis. It can present with purpura, weakness, and other systemic symptoms, often in association with hepatitis C infection or other chronic diseases.