Bonnet–Dechaume–Blanc syndrome

Overview

Bonnet–Dechaume–Blanc syndrome, also known as leptomeningeal angiomatosis with facial nevus or cerebrofacial arteriovenous metameric syndrome type 2 (CAMS-2), is a rare congenital neurocutaneous disorder. It is characterized by the triad of a facial port-wine stain (nevus flammeus), leptomeningeal vascular malformations (typically on the same side as the facial lesion), and ipsilateral cerebral arteriovenous malformations or other vascular anomalies. The condition is considered part of a spectrum that includes Sturge-Weber syndrome, but Bonnet–Dechaume–Blanc syndrome tends to have more severe and extensive vascular abnormalities within the brain and eye.

Causes

The exact cause of Bonnet–Dechaume–Blanc syndrome is not fully understood. It is believed to arise from somatic mutations during early embryonic development that affect the development of vascular and neural tissues in specific regions, leading to segmental (metameric) distribution of vascular anomalies. These mutations are not inherited and occur randomly in affected individuals. Recent studies suggest involvement of somatic activating mutations in the RASA1 or GNAQ genes, similar to those found in other vascular malformation syndromes.

Symptoms

Symptoms of Bonnet–Dechaume–Blanc syndrome vary based on the extent and location of vascular malformations but may include:

• Facial port-wine stain – usually in the ophthalmic (V1) distribution of the trigeminal nerve

• Leptomeningeal angiomatosis – abnormal vascular formations in the brain coverings, typically leading to seizures and neurological deficits

• Intracranial arteriovenous malformations (AVMs) – leading to increased risk of hemorrhage, headaches, or mass effect

• Visual disturbances – including glaucoma or optic atrophy if the eye is involved

• Seizures – often focal and resistant to medication, depending on brain involvement

• Hemiparesis or developmental delay – due to progressive neurological damage from vascular compromise

Diagnosis

Diagnosis of Bonnet–Dechaume–Blanc syndrome is clinical and radiologic, based on identifying characteristic features. Diagnostic steps may include:

• Clinical examination – identifying a port-wine stain, particularly in the V1 distribution

• Magnetic Resonance Imaging (MRI) – to visualize leptomeningeal enhancement or cortical atrophy

• Magnetic Resonance Angiography (MRA) or CT Angiography – to detect arteriovenous malformations and vascular anomalies

• Ophthalmologic evaluation – to assess for glaucoma or retinal involvement

• Electroencephalogram (EEG) – to evaluate seizure activity

Differentiation from other phakomatoses such as Sturge-Weber syndrome is essential, although some clinical overlap may occur.

Treatment

There is no cure for Bonnet–Dechaume–Blanc syndrome, and treatment is primarily symptomatic and supportive, involving a multidisciplinary approach. Management strategies include:

• Antiepileptic medications – to control seizures

• Laser therapy – for cosmetic or therapeutic treatment of facial port-wine stains

• Surgical or endovascular intervention – to treat high-risk or symptomatic intracranial AVMs or vascular malformations

• Physical and occupational therapy – for motor deficits or developmental delays

• Ophthalmologic care – including monitoring and treatment for glaucoma

• Regular neuroimaging and follow-up – to monitor for vascular changes or complications

Prognosis

The prognosis of Bonnet–Dechaume–Blanc syndrome varies depending on the severity and extent of intracranial involvement. Children with extensive brain vascular malformations may experience drug-resistant epilepsy, neurological impairment, and visual loss. Early diagnosis and comprehensive management can improve quality of life and reduce complications, though the condition often requires lifelong medical and neurological follow-up. In less severe cases, symptoms may be well controlled with appropriate intervention.