autosomal dominant osteopetrosis

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Autosomal dominant osteopetrosis is the less severe type of osteopetrosis and should be considered and compared with the other subtype autosomal recessive osteopetrosis. The autosomal dominant (AD) type is less severe than its autosomal recessive (AR) mate. Hence, it is also given the name "benign" or "adult" since patients survive into adulthood (something that is unlikely with the AR-type).

Clinical presentation

multiple fractures
multiple cranial nerve compression: e.g. leading to deafness and/or blindness
hepatosplenomegaly: from extramedullary hematopoiesis due to bone red marrow replacement

Pathology

In all osteopetrosis (whether AD or AR) there is a deficiency of osteoclast function and the result is that bone becomes dense. However, their altered internal architecture renders them weak. Therefore, patients have dense, sclerotic, fragile bones that fracture easily.

Classification

type I: pronounced osteosclerosis of cranial vault with clinical presentation as cranial nerve palsies
type II: end plate thickening of vertebrae (sandwich vertebra) and endobones ("bone-within-bone" appearance) in the pelvis, increased risk of fracture

Radiographic features

bone within a bone appearance (see case 1): one of the classical appearances of autosomal dominant osteopetrosis
Erlenmeyer flask type deformity of the tubular bones
sandwich vertebrae: diffuse endplate sclerosis (peripheral bony sclerosis) and lucency of the center of vertebral body
alternating radiolucent metaphyseal bands

Treatment and prognosis

Treatment is with bone marrow transplant and resultant normalization of bone production. Prognosis for the AD adult subtype is good with a reasonable life expectancy.

Differential diagnosis

General imaging differential considerations include: