Venous malformation
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# Overview
Venous malformations (VM) are simple vascular malformations. Clinically they can exhibit a wide range of manifestations. They may occur as isolated anomalies, combined with other vascular anomalies such as lymphatic malformations and venous malformations, or may occur as manifestations of multi-system syndromes. Their diagnosis and management depends on their clinical manifestations, histopathological behavior, and coexisting anomalies.

# Venous Malformations (VM)

## Common VM
- Localized defects characterized by dilated venous channels. Microscopically they consist of thin endothelial cells lined by fewer, disorganized smooth muscle cells and ]]extracellular]] matrix. Patient may present with deforming lesions, bleeding, thrombosis, significant acute or chronic pain, and pressure symptoms. Located on skin and mucosa for majority of the times, lesions often are present at birth.
- Sporadic mutations in the TEK gene, that encodes the tyrosine kinase receptor TIE2 that functions to regulate cellular growth and proliferation are found in half of the patients with sporadic venous malformations.
- Diagnosis is clinical. Current treatment options include sclerotherapy and surgery, alone or in combination but inaccessible lesions and high recurrence rate remains a problem. mTOR inhibitor rapamycin has been used in some studies with success.

## Familial VM cutaneo-mucosal (VMCM)
- Venous malformations that appear both on skin and mucous membranes.  Present at birth, they may not be apparent early in life and can appear after trauma and during pregnancy and puberty because of rapid growth. Patient may present with sequela of these malformations such as cosmetic deformation, pain, bleeding.
- Associated with mutation in TEK/TIE2 receptor tyrosine kinase that plays critical role in development of vessels and cardiovascular system.

## Blue rubber bleb nevus (Bean) syndrome VM
- Also called Bean's syndrome and diffuse angiomatosis, venous malformations in this disorder involve the skin, oral cavity and internal organs, most typically the gastrointestinal tract. Cutaneous malformations are bluish in color, generally smaller than 1-2 cm, often hyperkeratotic, compressible and often found at palms and soles. Anomalies on the skin are usually asymptomatic but GI malformations can cause hemorrhage that can lead to anemia, most frequent presentation in patient population. Other manifestation can include GI infarction, telescoping or twisting of GI tract leading to intussusception and volvulus.
- Thought to be caused by somatic double (cis) muatations in TEK gene although autosomal-dominant inheritance has also been described in some cases. The gene that encodes TIE2, receptor tyrosine kinase involved in cell-signaling.
- The documentation of gastrointestinal lesions by endoscopy, colonoscopy, CT scan or MRI is considered pathognomonic. Sclerotherapy and surgery such as enterotomy remain the mainstay of treatment along with symptomatic management such as long term iron supplementation and/or blood transfusions.
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## Glomuvenous malformation (GVM)
- Defined by presence of glomus cells in in smooth muscle layer of the vessels, these mesynchymal vascular anomaly arises from glomus bodies,arteriovenous anastomosis that help regulate temperature via shunting of blood through its unique neuromyoarterial structure. Classically found in digits, they can occur anywhere but widespread lesions are not common. Clinical presentation varies from asymptomatic bluish to reddish plaques and nodules that are often partially compressible and are tender to painful disfiguring lesions.
- Mutations in glomulin (GLMN) gene that leads to defective GLMN protein is thought to be the cause. GMLN protein binds Rbx1 and inhibits its E3 ubiquitin ligase activity. If GMLN is defective then it leads to increased activity of Rbx1 causing decreased levels of Fbw7 and thus increased levels of Cyclin E and c-Myc because Fbw7 facilitates the ubiquitination and degradation Cyclin E and c-Myc. Mutations are inherited in autosomal-dominant pattern with incomplete penetrance and variable expression although sporadic cases have been reported.
- Imaging such as MRI and CT scan and ultrasound can localize and define the extent of disease but definitive diagnosis requires biopsy following by histopathological studies demonstrating  proliferation of glomus cells and venous malformations. Current treatment modalities include surgical excision and sclerotherapy although recurrence is common. Recently electron beam radiation and Nd:YAG laser have been used with success.

## Cerebral cavernous malformation (CCM)
- Characterized by clusters of malformed endothelial channels forming densely arranged sinusoids that possess little to no intervening brain tissues. Because they lack smooth muscles and connective tissue and are malformed, they are prone to leakage causing micro-hemorrhages and thrombosis leading to hemosiderin deposits and gliosis around them. They can remain asymptomatic throughout life making them incidental finding but can cause symptoms associated with hemorrhage and pressure effects such as headaches, seizures, stroke, and focal neurologic deficits.
- Mutations in CCM1 Krev interaction trapped protein 1 (KRIT1), CCM2 Malcavernin, and CCM3 Programmed cell death protein 10 (PDCD10) are thought to be the cause of familial cases that tend to be inherited in autosomal-dominant pattern with incomplete penetrance, and variable expression. These proteins interact with cytoskeleton and endothelial tight junctions during vascular development in neural tissues to help maintain endothelial barrier function. they can occur due to sporadic mutations, usually presenting as single cavernous malformation while familial cases typically present as multiple cavernous malformations.
- Magnetic resonance (MR) imaging techniques are diagnostic modality of choice. Current treatment options depend on clinica history and location of the malformations. Surgery is usually preferred for symptomatic lesions in easily accessible locations and by some, for refractory epilepsy. If asymptomatic, observation is recommended but in case of single accessible asymptomatic malformation, surgical resection can be done. Surgery is also not recommended for malformations located in brainstem due to significant mortality and morbidity associated with surgery while some recommend surgery after a second symptomatic bleed. Guidelines for symptomatic lesions located deep vary. Radiosurgery can be an alternative modality for single, symptomatic lesion if risks associated with surgery are unacceptable.
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## Familial intraosseous vascular malformation (VMOS)
- Described as enlargement and expansion of malformed blood vessels that is severe and progressive, typically in skull, face, and vertebral column. Another typical finding is mid-line abnormalities such as diastasis recti, supraumbilical raphe, and hiatus hernia. Clinical presentation can vary but increasing intracranial pressure and hemorrhage after any surgical procedure such as extraction of tooth are of major concern. Other common findings include pain, enlarging tissues such as expanding jaw, bluish mass/swelling, loose tooth, spontaneous bleeding, and ulceration.
- Mutations in ELMO2 gene encoding engulfment and cell motility protein 2 (ELMO2) are thought to be the cause of these malformations. This protein s involved cell-signaling cascade through its attachment to cell membrane. Majority of the cases are sporadic but recently some familial cases with autosomal-recessive inheritance have been described.
- CT angiography and magnetic resonance techniques are the preferred diagnostic modalities and may show widening of neurovascular canal on CTA, hyperintense signal on MRI. Honeycomb and sunburst radiographic appearances have been described as well. Management options include embolization, sclerotherapy, and surgical extirpation.

## Verrucous venous malformation
- Formerly verrucous hemangioma, this rare congenital malformation is characterized by dilated blood vessels reaching out from papillary layer of dermis into subcutaneous tissue. Earlier presentation is bluish lesion that develops warty surface later on. Painful enlarging mass is the typical complain in symptomatic patients.
- Somatic mutation in MAP3K3 mitogen-activated protein kinase kinase kinase 3 are thought to be the cause.
- MRI is the diagnostic modality of choice but histopathological confirmation is gold standard for accurate diagnosis because of its close resemblance with angiokeratoma. Superficial ablation, surgical excision are treatment choices. Recently sirolimus has been used in some studies.