RT Journal Article SR Electronic T1 Managing challenging pain and irritability in OSTM1 mutation-related infantile malignant osteopetrosis JF BMJ Case Reports JO BMJ Case Reports FD BMJ Publishing Group Ltd SP e242498 DO 10.1136/bcr-2021-242498 VO 14 IS 5 A1 Alotaibi, Qutaibah A1 Dighe, Manjiri YR 2021 UL http://casereports.bmj.com/content/14/5/e242498.abstract AB Osteopetrosis describes a heterogeneous group of diseases characterised by increased bone density due to impaired osteoclast. The malignant infantile autosomal recessive (MIOP) form caused by mutations in OSTM1 is the most severe form of osteopetrosis. Children with this phenotype exhibit multisystemic complications, of which the neuropathic manifestations are the most severe. Infants with MIOP may present with pain and irritability that are likely to become continuous and debilitating as the disease progresses. There is limited understanding of the aetiology and management of pain in MIOP. Here, we describe a 2 month-old infant with OSTM1 mutation-related MIOP presenting with severe irritability and pain. This case provides the opportunity to discuss the cause and management of these distressing symptoms. We also review similar cases and the possible underlying mechanisms of pain and irritability to help provide a conceptual framework for the management of these symptoms in infants with OSTM1 MIOP.