Osteopetrosis in a six-month-old infant

Osteopetrosis is a severe and frequently fatal condition characterized by the formation of thick, dense bone, with a concomitant loss of bone marrow spaces secondary to defective osteoclast function or development. Clinical symptoms include pancytopenia, hepatosplenomegaly, fractures, cranial nerve impingement, and increased cranial pressure, among others. The condition requires rapid diagnosis and clinical intervention, as hematopoietic stem cell transplantation performed early in life can be curative in the majority of cases and can prevent the irreversible neurological impairment associated with the disease. We report a six-month-old male with osteopetrosis where bone marrow examination and molecular studies allowed a definitive diagnosis. Microscopic examination of a bone marrow biopsy demonstrated increased bone formation at various stages of ossification, decreased marrow spaces, and increased osteoclasts rimming the bone. Next-generation sequencing (NGS) demonstrated that the patient was homozygous for mutations in the TCIRG1 gene, which encodes an osteoclast vacuolar proton pump and is the most common mutation associated with the autosomal recessive or infantile malignant form of osteopetrosis. The patient underwent a cord blood stem cell transplant, but unfortunately expired four months after diagnosis. This case highlights the importance of bone marrow biopsy evaluation as part of the integrated approach to diagnosing osteopetrosis.