Intra-abdominal Streptococcus agalactiae infection associated with myelofibrosis treated with ruxolitinib: a case report of an atypical clinical presentation

Background Post-essential thrombocythemia myelofibrosis (post-ET MF) is a type of Philadelphia chromosome-negative MF. Patients with MF treated with ruxolitinib are immunosuppressed, and therefore more at risk of infection. Several opportunistic infections can occur in the first 6 months of ruxolitinib treatment. However, cases of MF complicated by intra-abdominal Streptococcus agalactiae infection during treatment with ruxolitinib are rare.Case report We report the case of a 42-year-old female patient who had resumed ruxolitinib at 20 mg twice daily on 28 February 2020 and was referred for management of JAK2V617F-positive post-ET MF on 24 April 2020. She complained of progressive abdominal distention 1 week before admission. During hospitalization, she experienced an abrupt episode of middle-grade fever without chills or peritoneal irritation. Subsequently, S. agalactiae (Group B Streptococcus, GBS) was isolated twice from ascites cultures, and an intra-abdominal infection was diagnosed. The infection was successfully treated using meropenem.Conclusions Our case indicates that ruxolitinib is a risk factor for GBS infection in MF patients. Accurate pathogen identification is critical for effective antimicrobial treatment and improved patient outcomes.