Malignant infantile osteopetrosis

Malignant infantile osteopetrosis, also known as infantile autosomal recessive osteopetrosis or simply infantile osteopetrosis is a rare osteosclerosing type of skeletal dysplasia that typically presents in infancy and is characterized by a unique radiographic appearance of generalized hyperostosis. The generalized increase in bone density has a special predilection to involve the medullary portion with relative sparing of the cortices. Obliteration of bone marrow spaces and subsequent depression of the cellular function can result in serious hematologic complications. Optic atrophy and cranial nerve damage secondary to bony expansion can result in marked morbidity. The prognosis is extremely poor in untreated cases. Plain radiography provides inestimable information to the diagnosis. Clinical and radiologic correlations are also fundamental to the diagnostic process. Additional gene testing is confirmatory.

Hematologic manifestations related to bone marrow suppression and subsequent pancytopenia are a major source of morbidity and mortality. Additionally extramedullary hematopoiesis can result in liver and spleen dysfunction. Cranial nerve dysfunction and neurologic complications are usually associated with infantile osteopetrosis. Expansion of the skull bone leads to macrocephaly. additionally Linear growth retardation that is not apparent at birth, delayed motor milestones and poor dentition can occur.

The generalized increase in bone density of the medullary portion predominates with relative sparing of the cortices. The axial and appendicular skeleton are uniformly involved. Malignant infantile osteopetrosis is known for exhibiting specific plain radiographic abnormalities:

Hematopoietic stem cell transplantation is the only effective line of treatment for malignant infantile osteopetrosis. It has been shown to provide long-term disease-free periods for a significant percentage of patients with malignant infantile osteopetrosis. It can impact both hematologic and skeletal abnormalities. Hematopoietic stem cell transplantation has been used successfully to reverse the skeletal abnormalities associated with malignant infantile osteopetrosis. Radiographs of patients with malignant infantile osteopetrosis have demonstrated bone remodeling and recanalization of medullar canals following hematopoietic stem cell transplantation. This favorable radiographic response could be expected within one year following hematopoietic stem cell transplantation. Nevertheless primary graft failure can prove fatal.

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