Perisplenic Retroperitoneal IgG4-Related Disease

A 72-year-old man visited a local physician with complaints of left upper quadrant abdominal pain and back pain in the left side. Abdominal US revealed a suspected splenic tumor, and the patient was referred to our hospital. Abdominal contrast-enhanced CT revealed hematoma around the spleen and spleen parenchyma of reduced density which was thought to be a splenic contusion. CT, performed while the patient was under observation, revealed enlargement of a soft tissue shadow around the splenic hilum region. PET/CT revealed increased uptake around the spleen. As malignant splenic tumor or pancreatic cancer could not be ruled out, we proceeded with surgery. The spleen was hard and swollen to a size larger than an adult’s fist, and adhered tightly to the stomach, transverse colon, and diaphragm. Splenectomy, distal pancreatectomy, partial resection of the stomach and transverse colon, and combined resection of the diaphragm were performed. A diagnosis of perisplenic retroperitoneal IgG4-related disease was made based on histopathological findings. The present case is among a group of diseases that manifest as enlargement and hypertrophy of organs throughout the body, high IgG4 levels in blood, and histologically prominent IgG4-positive plasma cell infiltration. This disease group occurs predominantly in the pancreas and retroperitoneum, but is rarely diagnosed based on findings of splenorrhagia.