Pembrolizumab
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Pembrolizumab Cytomegalovirus gastritis and unmasking of latent cytomegalovirus infection: case report
A 43-year-old woman developed cytomegalovirus (CMV) gastritis and unmasking of latent CMV infection during treatment with pembrolizumab for metastatic malignant melanoma. The woman presented with black skin lesions on the back and right upper buttock, as well as an enlarging non-tender right inguinal mass. She was subsequently diagnosed with metastatic malignant melanoma, clinical stage III. Thereafter, she underwent wide excision of skin. However, 1 month post-surgery, tests revealed enlarged lymph nodes in the right common iliac region. Hence, she started receiving pembrolizumab 200mg in cycles of 3 weeks [route not stated]. However, after 5 months, she developed epigastric discomfort after meals. Hence, she was hospitalised. The woman received hydration and unspecified treatment for pain. However, her symptoms markedly aggravated after cycle 9. She developed anorexia, severe epigastric pain, nausea and vomiting, scoring 7-8 points on the visual analogue scale. Pembrolizumab was withheld. Physical examination revealed tenderness to palpation of the epigastric region without rebound tenderness. Her vital signs were stable. She did not have a fever. Laboratory analyses indicated elevated serum amylase and lipase, and a decreased platelet count. Contrast-enhanced CT imaging of the abdominal revealed severe oedematous wall thickening of the stomach and duodenum, suggesting diffuse gastroduodenitis. Positive emission tomography/CT scan also revealed increased 18Ffluorodeoxyglucose uptake in the stomach, pancreas and duodenum, suggesting acute gastroduodenitis and pancreatitis without disease progression. Oesophagogastroduodenoscopy revealed diffuse, oozing, oedematous, haemorrhagic and exfoliative mucosa in the entire gastric wall, with several erosions in the second portion of the duodenum. These findings were consistent with acute haemorrhagic gastritis and suggested an immune-related adverse event (irAE) or CMV infection. Therefore, gastric wall biopsies were performed, and meanwhile, she was treated with dexamethasone due to the high suspicion for irAE. However, her symptoms remained unchanged, and she could not tolerate food intake. Three days later, hematoxylin and eosin staining revealed inflamed granulation tissue and necrotic detritus; immunohistochemical staining confirmed CMV infection. Hence, a diagnosis of CMV gastritis was made, and she was treated with ganciclovir. One week later, follow-up oesophagogastroduodenoscopy revealed improvement in the previously observed diffuse haemorrhagic mucosa of the stomach and oedematous mucosa of the duodenum. The woman resumed immunotherapy after 3 weeks of antiviral therapy [rechallenge outcome not stated]. Since she had neither experienced an irAE nor received any immunosuppression therapy during her preceding 8 cycles of pembrolizumab, it was concluded that pembrolizumab immunotherapy caused unmasking of a latent CMV infection, resulting in CMV gastritis. K
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