St to parkes-weber syndrome where there is a true arteriovenous malformation with high velocity blood flow. Aetiology and pathogenesis this is unknown, though several theories exist. Damage or malformation of the sympathetic ganglia in-utero, damage to deep veins leading to venous hypertension, or mesodermal maldevelopment causing the formation of microscopic arteriovenous communications have all been suggested. 1 the condition appears to be sporadic but there are families in whom the condition may be inherited in an autosomal dominant fashion with marked variation in penetrance. An abnormality in a gene locus on the long arm of chromosome 5 appears to be involved. 2 epidemiology this is a rare sporadic condition and there are no available figures for its annual incidence or prevalence in the population. Presentation the characteristic capillary haemangioma will be visible from birth in the vast majority of cases (98% in one series). 2 the skin lesion has a characteristic 'port-wine stain' appearance, being deep-purple in colour (in contrast to that of parkes-weber syndrome which appears bright red), with clear demarcation from normal skin. Varicosities and limb hypertrophy are not always present at birth and may take several years to manifest. Abnormal veins and marked varicosities may be present. Limb hypertrophy may begin by affecting the digits only and cause macrodactyly, syndactyly, polydactyly or oligodactyly. An increase in limb girth may be the only feature where soft tissues rather than bones are predominantly affected. Limb-lengthening may present initially as gait disturbance. If the head is affected then the syndrome may cause macrocephaly and/or mental retardation. viagra for sale viagra online cheap viagra cheap viagra online canadian pharmacy viagra for sale viagra online generic viagra online generic viagra online buy viagra online Lymphedema may complicate the condition and contribute to the limb enlargement. Rarely, the affected limb may show atrophy rather than hypertrophy. Thrombophlebitis is a common consequence in patients with large venous varicosities. If the cutaneous haemangioma is large it may cause a consumptive coagulopathy known as kasabach-merritt syndrome typified by anaemia, thrombocytopenia, prolonged prothrombin time (pt) and activated partial thromboplastin time (aptt), reduced fibrinogen levels, and elevation of fibrin degradation products. Pulmonary or venous thromboembolism may occur rarely as part of the kasabach-merritt syndrome. Other features include:1 spina bifida hypospadias hyperhidrosis hypertrichosis paraesthesiae decalcification of affected bones chronic venous insufficiency stasis dermatitis poor wound healing venous ulceration differential diagnosis parkes-weber syndrome (where there is a high-flow arteriovenous malformation rather than capillary haemangioma) sturge-weber syndrome (facial port-wine st. viagra side effects red eyes