Neurocutaneous melanocytosis

What it is

From: Orphanet

Neurocutaneous melanocytosis (NCM) is a rare congenital neurological disorder characterized by abnormal aggregations of nevomelanocytes within the central nervous system (leptomeningeal melanocytosis) associated with large or giant congenital melanocytic nevi (CMN). NCM can be asymptomatic or present as variably severe and progressive neurological impairment, sometimes resulting in death.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Generalized hirsutism · Very frequent (99-80%)

Abnormally increased hair growth over much of the entire body.

Increased CSF protein concentration · Very frequent (99-80%)

Increased concentration of protein in the cerebrospinal fluid.

Increased intracranial pressure · Very frequent (99-80%)

An increase of the pressure inside the cranium (skull) and thereby in the brain tissue and cerebrospinal fluid.

Intellectual disability · Very frequent (99-80%)

The term intellectual disability or intellectual developmental disorder is used to describe significantly sub-average intellectual and adaptive functioning based on clinical assessment and as measured by individually administered, appropriately normed, standardized and validated tests of intellectual functioning and adaptive behavior, with onset during the developmental period from infancy through adolescence.

Melanocytic nevus · Very frequent (99-80%)

A oval and round, colored (usually medium-to dark brown, reddish brown, or flesh colored) lesion. Typically, a melanocytic nevus is less than 6 mm in diameter, but may be much smaller or larger.

Seizure · Very frequent (99-80%)

A seizure is an intermittent abnormality of nervous system physiology characterized by a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain.

Thickened skin · Very frequent (99-80%)

Laminar thickening of skin.

Generalized hyperpigmentation · Very frequent (99-80%)

Numerous congenital melanocytic nevi · Very frequent (99-80%)

Hydrocephalus · Frequent (79-30%)

Hydrocephalus is an active distension of the ventricular system of the brain resulting from inadequate passage of CSF from its point of production within the cerebral ventricles to its point of absorption into the systemic circulation.

Papilledema · Frequent (79-30%)

Papilledema refers to edema (swelling) of the optic disc secondary to any factor which increases cerebral spinal fluid pressure.

Abnormality of neuronal migration · Occasional (29-5%)

An abnormality resulting from an anomaly of neuronal migration, i.e., of the process by which neurons travel from their origin to their final position in the brain.

Abnormality of retinal pigmentation · Occasional (29-5%)

Any deviation from the normal pigmentation of the retina.

Aphasia · Occasional (29-5%)

An acquired language impairment of some or all of the abilities to produce or comprehend speech and to read or write.

Other findings in the same source

From: Orphanet

Additional reported features include Atypical behavior (Occasional (29-5%)); Central scotoma (Occasional (29-5%)); Chiari malformation (Occasional (29-5%)); Chorioretinal coloboma (Occasional (29-5%)); Dandy-Walker malformation (Occasional (29-5%)); Death in infancy (Occasional (29-5%)); Dysphagia (Occasional (29-5%)); EEG abnormality (Occasional (29-5%)); Functional abnormality of the bladder (Occasional (29-5%)); Headache (Occasional (29-5%)). This is a selected summary, not a complete description of the condition.

When it may begin

From: Orphanet

Childhood

Inheritance in the source

From: Orphanet

Not applicable

Frequency and the population described

From: Orphanet

Point prevalence: 1-9 / 100 000; Europe; Value and class.

Which doctor should you see?

The suggested department for discussing Neurocutaneous melanocytosis is Dermatology, with a dermatologist as the relevant type of clinician. Dermatologist; paediatric services for children as appropriate.

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.

• Which features of the skin, hair or nails distinguish the possibilities?
• Would photographs over time help document the changes?
• What should be expected from treatment, and how will irritation or other adverse effects be managed?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Neurocutaneous melanocytosis. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

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.