A case of eculizumab-induced hemophagocytic lymphohistiocytosis (HLH) in a myasthenia gravis patient

Hemophagocytic lymphohistiocytosis (HLH) is an immune hyperactivation state that can occur in immunosuppressed patients and is associated with high mortality and worse prognosis. We present a case of 78-year-old patient on multiple immune suppressing medications, including eculizumab and azathioprine for myasthenia gravis, who presented to our hospital for evaluation of hyperbilirubinemia. She had extensive laboratory workup that was significant for anemia, thrombocytopenia, increased ferritin level, and hyponatremia. Additionally, she had increased CD25 and CXCL9 leading to the diagnosis of HLH. Investigations for triggering factors identified eculizumab after excluding multiple infectious and rheumatologic conditions. Unfortunately, the patient did not survive. We recommend evaluating for high ferritin as a reliable predictor for HLH for patients on myasthenia gravis on eculizumab.