Osteopoikilosis is a sclerosing bony dysplasia characterised by multiple benign enostoses. It is a rare inherited benign condition incidentally found on skeletal x-rays. Its importance is predominantly in correct diagnosis so that it is not mistaken for pathology.
The bone islands of osteopoikilosis develop during childhood and do not regress and therefore are seen in all age groups. There is no gender predilection.
Osteopoikilosis is inherited as an autosomal dominant disorder 1 .
The condition is asymptomatic and does not degenerate into malignancy. Bone strength is normal.
Histologically the bone islands found in osteopoikilosis and in sporadic enostoses are merely patches of dense cortical like bone complete with haversian canals located within the spongiosa, often just deep to the cortex 7 .
A closely related entity is Buschke-Ollendorff syndrome.
Osteopoikilosis is often found concurrently with osteopathia striata, and melorheostosis, and it is thought by some that they represent a spectrum of the same condition. Indeed recent genetic evidence suggests that these conditions are related by a loss of function mutation of the LEMD3 gene 2.
- Gunal-Seber-Basaran syndrome: osteopoilkilosis with dacrocystitis
- mixed sclerosing bone dysplasia: concurrent osteopoikilosis, osteopathia striata and melorheostosis8.
- tendency to keloid formation 7
Plain film and CT
The bone islands of osteopoikilosis are typically clustered around joints and align themselves parallel to surrounding trabeculae (thus predominantly longitudinally in the epiphyses and metaphyses) 8. Most lesions are found in the appendicular skeleton and pelvis. The axial skeleton is largely spared. It is rare for the skull vault to be involved 6.
The lesions vary in size, usually a 5-10 mm, but ranging from only 1-2 mm up to 1-2 cm.
Appearances on MRI are the same as individual bone islands. Each lesion is small and dark on both T1 and T2 weighted images, as it is composed of mature dense bone 3.
Bone scan should not demonstrate any increase in uptake, useful if metastatic disease is considered in the differential.
Osteopoikilosis is one of the skeletal “don’t touch” lesions.
When seen throughout multiple bones with characteristic appearances, there is little differential. When only a few lesions are seen on an isolated film, the differential includes:
- incidental bone islands (enostoses)
- other sclerosing bone dysplasias
- sclerotic metastases (rarely involve epiphyses)
- osteoid osteoma: only rarely multiple 4
- chronic multifocal sclerosing osteomyelitis
- calcium and phosphate metabolism abnormalities
- Erdheim-Chester disease
- previous instrumentation/fractures/avascular necrosis
- Paget disease
The differential diagnosis for bone tumours is dependent on the age of the patient, with a very different set of differentials for the paediatric patient.
- bone-forming tumours
- cartilage-forming tumours
- chondromyxoid fibroma
- fibrous bone lesions
- bone marrow tumours
- other bone tumours or tumour-like lesions
- aneurysmal bone cyst
- benign fibrous histiocytoma
- giant cell tumour of bone
- Gorham massive osteolysis
- haemophilic pseudotumour
- intradiploic epidermoid cyst
- intraosseous lipoma
- musculoskeletal angiosarcoma
- musculoskeletal haemangiopericytoma
- primary intraosseous haemangioma
- simple bone cyst
- impending fracture risk
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- 8. Ghai S, Sharma R, Ghai S. Mixed sclerosing bone dysplasia-a case report with literature review. Clin Imaging. 2003;27 (3): 203-5. Pubmed citation