Osteopetrosis

Osteopetrosis, also known as Albers-Schönberg disease or marble bone disease, is an uncommon hereditary disorder that results from defective osteoclasts. Bones become sclerotic and thick, but their abnormal structure actually causes them to be weak and brittle.

There are two separate subtypes of osteopetrosis:

• infantile autosomal recessive osteopetrosis

• benign adult autosomal dominant osteopetrosis

Clinical presentation

Presentation, in the majority of cases, is with a fracture due to weakened bones. Fractures are often transverse with multiple areas of callus formation and normal healing.

Additionally, there is crowding of the marrow, so bone marrow function is affected resulting in myelophthisic anemia and extramedullary hematopoiesis with splenomegaly. This may terminate in acute leukemia.

Pathology

Both forms are congenital abnormalities with localized chromosomal defects. These result in defective osteoclasts and overgrowth of bone. The bones become thick and sclerotic, but their increased thickness does not improve their strength. Instead, their disordered architecture results in weak and brittle bones. The osteoclasts' lack of carbonic anhydrase leads to inability to acidify Howship lacunae in bone. Chloride channel dysfunction can also lead to osteopetrosis.

Radiographic features

The features are dependent on the subtype of osteopetrosis and are detailed in the individual articles:

• infantile autosomal recessive osteopetrosis

• benign adult autosomal dominant osteopetrosis

Treatment and prognosis

Treatment is with bone marrow transplant and resultant normalization of bone production. The prognosis for the autosomal dominant adult subtype is good with a normal life expectancy. However, the autosomal recessive infantile subtype can result in stillbirth or death in infancy, with few patients living past middle age.

History and etymology

The term is derived from the Greek words 'osteo' meaning bone and 'petros' meaning stone. It was first described by German radiologist Heinrich Ernst Albers-Schönberg (1865-1921) in 1904 ^4,6. Interestingly Albers-Schonberg was the first Professor of Radiology in Germany - and perhaps globally - the Chair was bestowed on him by the University of Hamburg in 1919 ⁶. 

Differential diagnosis

General imaging differential considerations include:

• heavy metal poisoning (e.g. lead)

• melorheostosis

• hypervitaminosis D

• pyknodysostosis

• fibrous dysplasia of skull or face

See also

• generalized increased bone density (mnemonic)

• generalized increased bone density in children

• generalized increased bone density in adults