What is phakomatosis pigmentovascularis?
Phakomatosis pigmentovascularis (PPV) is a rare congenital syndrome, predominantly consisting of a vascular malformation and dermal melanosis.
PPV is a mosaic abnormality of vasomotor nerves and melanocytes resulting in its characteristic cutaneous manifestations. A small proportion of patients have associated systemic features.
Who gets phakomatosis pigmentovascularis?
Due to its rarity, the prevalence is currently unknown. It is thought to be more common in those of Asian ethnicity. There is some overlap with Klippel-Trenaunay and Sturge-Weber syndromes.
What causes phakomatosis pigmentovascularis?
PPV is a mosaic developmental abnormality of the vasomotor nerves and melanocytes (derived from the neural crest).
It is caused by sporadic mutations in GNA11 and GNAQ genes, which encode Gα subunits of heterotrimeric G proteins. These genetic mutations have been detected in affected tissues, but undetectable in the blood, suggesting it is a post-zygotic mosaic disorder.
What are the clinical features of phakomatosis pigmentovascularis?
PPV usually consists of a vascular component, most commonly a capillary malformation and extensive dermal melanosis, such as a naevus of Ota or lumbosacral dermal melanocytosis (Mongolian spot).
There are a number of other cutaneous associations depending on the subtype, such as:
There are five types of phakomatosis pigmentovascularis. These are distinguished based on cutaneous signs. Each type is further divided into subtypes A and B, depending on whether there is systemic involvement (as evident in subtype B). Type ll is the most common (port-wine stain with dermal melanosis).
Table 1. Types of phakomatosis pigmentovascularis
|I||Capillary malformation, epidermal naevus|
|II (Cesioflammea)||Capillary malformation, dermal melanosis (lumbosacral dermal melanocytosis, nevus of Ota)|
|III (Spilorosea)||Capillary malformation, naevus spilus, naevus anaemicus|
|IV (Unclassified)||Capillary malformation, dermal melanosis (lumbosacral dermal melanocytosis, naeus of Ota), naevus spilus, naevus anaemicus|
|V (Cesiomarmorata)||Cutis marmorata telangiectatica congenita, dermal melanosis (lumbosacral dermal melanocytosis, naevus of Ota)|
Phakomatosis pigmentovascularis has been associated with a variety of systemic abnormalities. These are only present in a small proportion of patients.
Systemic features can include:
- Ocular (glaucoma, uveal melanoma)
- Neurological (seizures, intracranial vascular abnormalities, calcifications, cerebral atrophy, bilateral deafness, facial paralysis, hydrocephalus, diabetes insipidus, plexiform neurofibroma)
- Musculoskeletal (limb length discrepancies, scoliosis, spina bifida, premature eruption of teeth)
- Renal agenesis.
How do clinical features vary in differing types of skin?
Phakomatosis pigmentovascularis is most common in the darker skin types seen in Asian ethnicities. The dermal melanosis presents as a blue/grey pigmentation and can be mistaken for bruising. The erythema associated with vascular malformations can be less prominent in darker skin types.
What are the complications of phakomatosis pigmentovascularis?
The complications associated with phakomatosis pigmentovascularis depend on any associated systemic involvement.
Complications can include:
- Visual impairment
- Intellectual impairment
- Hearing impairment
- Back pain
- Impaired mobility.
How is phakomatosis pigmentovascularis diagnosed?
Phakomatosis pigmentovascularis is a clinical diagnosis based on the combination of the associated cutaneous findings.
Specific genetic analysis of affected tissues can be performed.
What is the differential diagnosis for phakomatosis pigmentovascularis?
- Sturge Weber syndrome
- Klippel-Trenaunay syndrome
- Idiopathic vascular malformation and/or dermal melanosis.
What is the treatment for phakomatosis pigmentovascularis?
No treatment is required for the capillary malformation or dermal melanosis. If treatment is desired for cosmetic reasons, laser treatment can be used, such as:
- Pulsed dye laser for capillary malformation
- Q-switched laser for pigmentary changes.
- Screening MRI brain is generally recommended
- Ophthalmology referral if naevus of Ota present
- Other screening tests and referrals depending on clinical findings.
What is the outcome for phakomatosis pigmentovascularis?
The recurrence risk of phakomatosis pigmentovascularis in subsequent pregnancies is close to zero given it is associated with a mosaic issue and normal egg and sperm. This is true for both the parents of the affected child and the affected child’s future offspring.