Idiopathic duct-centric pancreatitis: Disease description and endoscopic ultrasonography-guided trucut biopsy diagnosis

Background/Aims: Recent data demonstrate the presence of two autoimmune pancreatitis (AIP) subtypes. All existing endoscopic ultrasonography-guided trucut biopsy (EUS-TCB) data pertain to type 1 disease. Our aim is to determine if EUS-TCB samples are sufficient for diagnosing type 2 AIP. Methods: This is a retrospective case series conducted in an academic tertiary care center. Patients included those with type 2 AIP (n = 5), retrospectively identified from a database of all patients with AIP, diagnosed by HISORt criteria (n = 125). The primary outcome measure was the diagnostic capability of EUS-TCB for type 2 AIP. Results: 5 patients (4 male, 1 female; mean age 39.6 years) who underwent EUS-TCB were diagnosed with type 2 AIP. The serum IgG₄ level was elevated in 1 of the 4 patients tested. CT/MRI revealed diffuse pancreas enlargement (n = 3), a pancreas head mass (n = 1), and a normal pancreas (n = 1). Prior to EUS, AIP was not specifically suspected, but part of a broad differential (n = 3) or not suspected at all (n = 2). Fine-needle aspiration was negative for neoplasia and AIP. The TCB histology was definitive (n = 4) or suggestive (n = 1) for type 2 AIP. No complications developed. Conclusions: EUS-TCB may be safe and may provide sufficient material to definitively diagnose type 2 AIP.