Background: Henoch-Schönlein purpura (HSP) is the most common systemic vasculitis in children. It usually shows palpable purpura, joint pain,kidney involvement and acute abdominal pain. In 10–40% of patients, gastrointestinal manifestations may precede the onset of skin, purpura therefore it is sometimes difficult to make a precise diagnosis in early phase. 
Objective: Our objective is to clarify the clinical characteristics of HSP in which abdominal pain precedes joint and skin manifestations. Method: Children less than 15 years old who were diagnosed as HSP and admitted to Himeji Red Cross Hospital from April 1, 2012 to July 31, 2018 were included in this study. Clinical data was collected from medical records. A retrospective analysis of clinical manifestations, laboratory data and findings of abdominal ultrasonography were conducted. Diagnosis of HSP based on criteria for American College of Rheumatology. We defined HSP-A as a patient who showed abdominal pain more than 24 hour before appearing skin or joint manifestations. 
Result: We found 85 HSP case and in which 13 cases (15.2%) was HSP-A. There were no difference about gender and age between HSP-A and non HSP-A. Otherwise, In HSP-A group, Factor XIII was significantly low compared with that of non HSP-A group (65.8 vs 34.3 %, P<0.05). Thickening in duodenum to small intestine was found by abdominal ultrasound in HSP-A more than non HSP-A. 
Conclusion: We reveal that in HSP-A patients, Factor XIII was low and Intestinal thickening in duodenum to small intestine was seen in ultrasonography in early phase. An abdominal ultrasonography might be useful for early diagnosis of HSP-A. (259 words)