A 15-year old Hispanic male with asthma presented with 1-week of hematemesis, melena, and 1month 10 lb weight loss. His hemoglobin was 7.7 g/dL, and he received a red blood cell transfusion and intravenous acid blockade medication. His white blood cells, platelets, electrolytes, albumin, and international normalized ratio were normal. Initial endoscopic features showed focal ecchymoses, diffuse mucosal nodularity, and oozing; however, specimen pathology lacked significant abnormalities. Abdominal CT and PET scan demonstrated gastric wall thickening, nodularity, and hypermetabolic activity, respectively. Oncology recommended full-thickness biopsies to better evaluate for malignancy. Repeat endoscopy with surgical laparoscopic mucosal resection and wedge biopsies revealed a markedly thickened muscular wall and chronic inflammation (Fig. 1). Workup for malignancies, infections, rheumatologic or autoinflammatory disorders was negative. Subsequent esophagogastroduodenoscopy and lacrimal duct specimens were obtained to perform additional diagnostic tissue staining and were Congo red positive with birefringence via polarized light, consistent with amyloid deposition (Fig. 2). LC-MS/MS confirmed AL (lambda)-type amyloid deposition. Pulmonary function tests and echocardiogram were normal.Amyloidosis is a group of hereditary or acquired diseases marked by systemic or localized amyloid deposition leading to progressive organ dysfunction (1). An accumulation of abnormal proteins occurs in immunoglobulin light chain (AL) amyloidosis and aging-associated amyloidosis (1,2). Conversely, an excess of normal proteins occurs in systemic (AA) amyloidosis or ß2-microglobulin amyloidosis (1). Gastrointestinal manifestations of amyloidosis include dysmotility, malabsorption, and bleeding (2). Previous case reports described adult amyloidosis patients with gastrointestinal involvement presenting with hematemesis (3,4). We report a rare pediatric case of systemic AL amyloidosis presenting with upper gastrointestinal bleeding.

1107 Figure 2 PCA was used to characterize the variability in cell subset frequencies across LN patients. (A) The first PC, representing the balance between lymphoid cells and monocytes/macrophages, was found to be significantly correlated with the Chronicity index. (B) The fourth PC, representing the degree of macrophage differentiation, was found to be significantly correlated with the Activity index. Shown in each case are the Spearman correlation and its associated p-value.