Osteopetrosis, a rare congenital genetic disease characterized by increased bone density due to impaired bone resorption by osteoclasts. It is classified into three forms: Infantile malignant autosomal recessive (AR) osteopetrosis, intermediate (AR) osteopetrosis and autosomal dominant (AD) osteopetrosis. Incidence of infantile malignant AR is 1/2,00,000 and if untreated has a fatal outcome. The condition is commonly diagnosed in infancy with symptoms of significant hematologic abnormalities with bone marrow failure, hepatosplenomegaly, macrocephaly with frontal bossing and bone fractures. Because of rarity of this type of malignant infantile form of osteopretrosis, we like to report this case of malignant infantile osteopetrosis who presented with bronchopneumonia, anemia with melaena at 2 months 15 days of age.