Abstract
Osteopetrosis is a rare genetic disease of bone resorption. It includes a variety of hereditary skeletal disorders that have the main radiographic feature of increased bone density and thickness due to differentiation or functional defects in osteoclast. The clinical presentation varies widely based on the type of osteopetrosis and ranges in severity from asymptomatic to a fatal course. Our case is of the infantile malignant osteopetrosis (IMOP) form. It is inherited as an autosomal recessive pattern that generally starts in intrauterine life and manifests at birth or early childhood. It is the most severe form and has an incidence of 1 in 250,000 births. The patient presented at the age of two months with a history of recurrent fever, recurrent pneumonia, developmental delay, and infantile spasms. Upon examination, she was found to have hepatosplenomegaly, axial hypotonia, limb spasticity, and visual impairment. Genetic testing revealed a homozygous variant of OSTM1 gene, which is a known Saudi mutation of autosomal recessive osteopetrosis (ARO). IMOP should be considered as a rare differential of hepatosplenomegaly. Early diagnosis by clinical picture, imaging, and genetic testing is important to direct the appropriate management in order to prevent disease progression before the irreversible neurological sequelae occur. Patients should be managed by a comprehensive approach, and currently, hematopoietic stem cell transplantation (HSCT) provides a better outcome for IMOP patients.