Haemophagocytic lymphohistiocytosis in pregnancy and the postpartum: a case series from the national HLH network

Haemophagocytic lymphohistiocytosis (HLH) is a hyperinflammatory sepsis-like syndrome that accounts for 1% of maternal deaths in the United Kingdom (UK). In 2019, a UK-wide HLH network was developed to provide specialist advice for patients with HLH. Until September 2024, eight individuals had been referred to this service with HLH onset during pregnancy or within 6 months postpartum, and this article summarises their management. Shared themes were of postpartum predominance, with onset typically within a month of delivery, preceding infection, and underlying immune dysfunction. Common therapies included corticosteroids and the interleukin-1 receptor antagonist, anakinra. Most individuals required level 3 care, three were considered for extracorporeal membrane oxygenation, and one died. HLH should be included in the differential of maternal sepsis, given all cases presented with fever and organ dysfunction, particularly if there is ongoing deterioration despite antimicrobial therapy and/or without an identified source.