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Angio-osteohypertrophic (AOH) syndrome is a congenital vascular bone syndrome (CVBS) characterized by the presence of a vascular malformation in a limb, mainly of the arteriovenous type, which results in overgrowth of the affected limb.
Prevalence is unknown but around 1,000 cases have been reported in the literature so far.
The affected limb may show overgrowth in comparison with the contralateral limb and the extent of this limb length discrepancy (LLD) may vary from a slight difference to 10 cm or more. The growth effect may be manifested in only one bone (mainly the femur or tibia) or, in some cases, affect the whole limb. The LLD may become apparent during infancy, childhood or adolescence and is clearly visible by comparison of the level of the gluteal and posterior knee folds. Collateral signs may include a cutaneous nevus, dilated superficial veins, limb enlargement, skin warming, dermatitis, ulcers and bleeding. However, these signs are not always present. The existence of AV fistulas around or inside the bone is now being widely accepted as the main cause of bone overgrowth and the older theory that venostasis may cause the bone growth alterations is being largely discounted. The arteriovenous malformations (AVMs) may affect bone metabolism, stimulating limb elongation during the growing period. After the physiologic end of bone growth, no further change in bone length is possible. Some cases of CVBS with venous anomalies (such as deep venous aplasia) have been observed but angiographic studies demonstrated that in these cases opening of an AV communication resulted in stimulation of the bone growth.
Recently, several different molecules with both angiogenic and osteogenic activity have been identified and their role in CVBS needs to be investigated.
Diagnosis is made by clinical examination with a combination of plain X-ray studies (preferably in the standing position to identify the LLD and any changes in bone structure), and various techniques for detecting and establishing the site of the AVM: duplex scan, angiography (although it may fail to demonstrate intraosseous fistulas), angioscintigraphy (whole blood pool scan), a labeled microspheres test, direct percutaneous puncture of abnormal bone areas with contrast injection, and angio-MRI, -CT and -3D CT scans.
The differential diagnosis should include venous dysplasias, lymphedema and bone tumors.
Although AOH syndrome generally appears to be sporadic, autosomal dominant inheritance has been noted in a few families.
Management and treatment
In childhood, during the growth period, treatment of the AVM should be performed and may lead to spontaneous correction of the LLD. Intraosseous AVMs should be treated by direct puncture and occlusion, or possibly by catheter embolization, but surgery should be avoided as the risk of hemorrhage is high. Soft tissue fistulas can be treated by catheter embolization or by surgery with resection of the fistulous area, alone or in combination with endovascular procedures. Orthopedic procedures should stop the bone elongation during the growth period or correct the LLD in adults. Epiphyseal staples are also effective at stopping growth. Contralateral limb elongation using the Ilizarov technique is feasible in adults.
If recognized early and treaded correctly during childhood, results may be good or excellent. In adults, orthopedic interventions are able to correct the LLD.
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