Differential Diagnosis for Elevated Atypical p-ANCA
Elevated atypical p-ANCA (perinuclear anti-neutrophil cytoplasmic antibodies) can be associated with various autoimmune and inflammatory conditions. Here's a categorized differential diagnosis:
Single Most Likely Diagnosis
- Microscopic Polyangiitis (MPA): This condition is a form of vasculitis that affects small-sized blood vessels. Atypical p-ANCA is commonly found in MPA, making it a leading consideration in the differential diagnosis.
Other Likely Diagnoses
- Eosinophilic Granulomatosis with Polyangiitis (EGPA): Formerly known as Churg-Strauss syndrome, EGPA is another type of vasculitis that can present with atypical p-ANCA positivity, especially in the context of asthma and eosinophilia.
- Inflammatory Bowel Disease (IBD): Both Crohn's disease and ulcerative colitis can be associated with atypical p-ANCA. The presence of these antibodies, particularly in ulcerative colitis, can help differentiate it from Crohn's disease, where cytoplasmic ANCA (c-ANCA) might be more commonly seen.
- Primary Sclerosing Cholangitis (PSC): This chronic liver disease often associated with IBD can also present with atypical p-ANCA.
Do Not Miss Diagnoses
- Wegener's Granulomatosis (Granulomatosis with Polyangiitis, GPA): Although c-ANCA is more commonly associated with GPA, atypical p-ANCA can occasionally be present. GPA is a serious condition that requires prompt treatment to prevent organ damage.
- Systemic Lupus Erythematosus (SLE): While SLE can present with a wide range of autoantibodies, atypical p-ANCA can be seen in some cases. Missing SLE could lead to delayed diagnosis and treatment of a potentially severe disease.
Rare Diagnoses
- Relapsing Polychondritis: A rare autoimmune disorder characterized by recurrent episodes of cartilaginous inflammation, which can occasionally be associated with atypical p-ANCA.
- Autoimmune Hepatitis: Some forms of autoimmune hepatitis may present with atypical p-ANCA, although this is less common than other autoantibodies like ANA or anti-smooth muscle antibodies.