Microcephaly-capillary malformation syndrome

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Microcephaly-capillary malformation syndrome is an inherited disorder characterized by an abnormally small head size (microcephaly) and abnormalities of small blood vessels in the skin called capillaries (capillary malformations).

In people with microcephaly-capillary malformation syndrome, microcephaly begins before birth and is associated with an unusually small brain and multiple brain abnormalities. Affected individuals develop seizures that can occur many times per day and are difficult to treat (intractable epilepsy). The problems with brain development and epilepsy lead to profound developmental delay and intellectual impairment. Most affected individuals do not develop skills beyond those of a 1- or 2-month-old infant. For example, most children with this condition are never able to control their head movements or sit unassisted.

Capillary malformations are composed of enlarged capillaries that increase blood flow near the surface of the skin. These malformations look like pink or red spots on the skin. People with microcephaly-capillary malformation syndrome are born with anywhere from a few to hundreds of these spots, which can occur anywhere on the body. The spots are usually round or oval-shaped and range in size from the head of a pin to a large coin.

Other signs and symptoms of microcephaly-capillary malformation syndrome include abnormal movements, feeding difficulties, slow growth, and short stature. Most affected individuals have abnormalities of the fingers and toes, including digits with tapered ends and abnormally small or missing fingernails and toenails. Some affected children also have distinctive facial features and an unusual pattern of hair growth on the scalp.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Microcephaly-capillary malformation syndrome results from mutations in the STAMBP gene. This gene provides instructions for making a protein called STAM binding protein. This protein plays a role in sorting damaged or unneeded proteins so they can be transported from the cell surface to specialized cell compartments that break down (degrade) or recycle them. This process helps to maintain the proper balance of protein production and breakdown (protein homeostasis) that cells need to function and survive. Studies suggest that STAM binding protein is also involved in multiple chemical signaling pathways within cells, including pathways needed for overall growth and the formation of new blood vessels (angiogenesis).

Mutations in the STAMBP gene reduce or eliminate the production of STAM binding protein. This shortage allows damaged or unneeded proteins to build up inside cells instead of being degraded or recycled, which may damage cells and cause them to self-destruct (undergo apoptosis). Researchers suspect that abnormal apoptosis of brain cells starting before birth may cause microcephaly and the underlying brain abnormalities found in people with microcephaly-capillary malformation syndrome. A lack of STAM binding protein also alters multiple signaling pathways that are necessary for normal development, which may underlie the capillary malformations and other signs and symptoms of the condition.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

This condition has an autosomal recessive pattern of inheritance, which means both copies of the STAMBP gene in each cell have mutations. An affected individual usually inherits one altered copy of the gene from each parent. Parents of an individual with an autosomal recessive condition typically do not show signs and symptoms of the condition.

At least one individual with microcephaly-capillary malformation syndrome inherited two mutated copies of the STAMBP gene through a mechanism called uniparental isodisomy. In this case, an error occurred during the formation of egg or sperm cells, and the child received two copies of the mutated gene from one parent instead of one copy from each parent.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Microcephaly-capillary malformation syndrome is rare. About a dozen people have been diagnosed with the disorder.

Which doctor should you see?

The suggested department for discussing Microcephaly-capillary malformation syndrome is Clinical Genetics, with a clinical geneticist as the relevant type of clinician. Paediatrician (children) or physician (adults), with clinical geneticist referral.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Does the exact genetic or chromosome finding explain the observed features?
• Would a genetic counsellor help the family understand the result?
• Which organ-specific assessments are appropriate for this particular diagnosis?

Treatment discussions and follow-up

Where the source describes treatments, these are an overview of possible care, not a prescription for an individual. Ask which option applies to the confirmed diagnosis, what benefit is expected, what adverse effects to watch for and how progress will be assessed. Availability, approvals and local practice can differ from the country described in the source.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.