Birthmarks and congenital naevi

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Birthmarks include developmental collections or malformations of melanocytes, vessels, epidermal structures and dermal cells. History should establish onset, evolution, symptoms, previous trauma or treatment and whether there are neurological, ocular, skeletal or developmental features. Examine the whole skin in good light, record surface, palpability, blanching, border, colour and distribution, and plot growth against the child's body rather than interpreting change from memory. In richly pigmented skin, subtle pink vascular marks may be easier to recognise by blanching, warmth or texture, while pigmentary borders may require tangential light and comparison with nearby skin.

Congenital melanocytic naevi range from small macules to extensive plaques with variable hair, nodules and satellites. Risk is not uniform: larger projected adult size, axial or posterior location, numerous satellites and neurological features increase concern for melanoma or melanocytic deposits in the central nervous system. Benign proliferative nodules can grow in infancy, but a new firm, ulcerating, bleeding or disproportionately enlarging focus still needs expert assessment. Removing a visible naevus may improve symptoms or appearance but cannot remove melanocytes elsewhere and does not abolish melanoma risk.

Families need a named route for change, not simply reassurance. Agree whether the child needs discharge with self-monitoring, dermatology surveillance, plastic-surgery discussion, ophthalmology, neurology or clinical genetics. Explain uncertainty in plain language and include the child as maturity allows. Clinical photography should be necessary, consented and stored within policy; intimate lesions require particular attention to assent, chaperoning and restricted access. Management decisions should balance anaesthetic and scar burden, function, surveillance feasibility and the child and family's priorities.

Key points

First decide whether a mark is melanocytic, vascular, epidermal or pigmentary and whether it was truly present at birth or became visible during infancy.
Congenital melanocytic naevi are brown to black, sometimes hairy plaques whose projected adult size, anatomical site and satellite count guide melanoma and neurocutaneous-melanocytosis risk.
Most small solitary congenital naevi need baseline documentation and change-aware follow-up rather than prophylactic excision solely to prevent melanoma.
A new persistent hard or rapidly growing nodule, ulcer, unexplained bleeding or focal colour and texture change needs urgent dermoscopic assessment and often biopsy.
Café-au-lait macules are smooth uniformly pigmented patches; six or more, segmental clustering or associated freckling and developmental signs should trigger a neurocutaneous assessment.
Congenital dermal melanocytosis is a flat blue-grey patch, commonly sacral, which may resemble bruising; record its site and appearance early without assuming trauma.
Naevus simplex is a blanching midline pink patch that usually fades, whereas a capillary malformation is persistent, often unilateral and may deepen or thicken with age.
A forehead or upper-eyelid capillary malformation can mark Sturge–Weber and glaucoma risk and warrants early specialist ophthalmic and paediatric assessment.
Serial photographs require informed consent, a scale, constant lighting and secure clinical storage; images complement rather than replace palpation and dermoscopy.
Discuss cosmetic visibility, hair, clothing friction, bullying and family language without implying that treatment is required for social acceptability.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Post-zygotic melanocyte change

Many congenital melanocytic naevi arise from mosaic variants acquired during embryogenesis, producing a lesion distribution and burden not necessarily present in parental blood.

Capillary developmental malformation

Persistent capillary malformations result from local vascular-development signalling differences and grow with the child rather than entering the proliferative and involution phases of haemangioma.

Dermal melanocyte persistence

Congenital dermal melanocytosis reflects melanocytes remaining deep in dermis during migration, creating blue-grey colour through optical scattering.

Neurocutaneous mosaicism

Some pigmentary or vascular marks share an embryological mosaic cause with eye, brain, bone or peripheral-nerve manifestations.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Naevomelanocytic proliferation
Congenital naevus cells occupy epidermal, dermal and sometimes deeper structures, explaining hair, nodules and incomplete removal by superficial procedures.
2
Melanocytes outside the skin
In higher-burden CMN, melanocytic deposits can affect leptomeninges and brain, causing seizures, hydrocephalus, focal deficits or developmental problems.
3
Persistent ectatic capillaries
Capillary malformations remain dilated and may progressively darken, thicken and form nodules rather than spontaneously involuting.
4
Age-dependent expression
Hair, surface thickness, neurofibromas, freckling and other syndrome clues may emerge over years, so a newborn examination cannot exclude a later phenotype.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Congenital melanocytic naevus

A brown, black, blue-black or skin-coloured macule or plaque present at birth or apparent in early infancy may become thicker or hairier as the child grows and can have smaller satellite naevi.

Concerning change within a naevusRed flag

A focal hard nodule, rapid growth out of proportion to the child, persistent ulceration, spontaneous bleeding, pain or new regional nodes is a diagnostic change rather than a routine cosmetic issue.

Café-au-lait pattern

Uniform tan to brown macules with smooth borders are often isolated; multiplicity, axillary or groin freckling, neurofibromas, segmental distribution or developmental signs changes the syndromic probability.

Congenital dermal melanocytosis

A non-tender flat slate-grey, blue or blue-brown patch, classically over sacrum or buttocks, lacks the evolution and tenderness of an acute bruise and often fades during childhood.

Naevus simplex

A pale pink blanching patch on glabella, eyelids or nape becomes more visible with crying and usually lightens without treatment.

Capillary malformation

A persistent pink, red, violaceous or dark patch follows a vascular territory, does not involute and may thicken or develop nodules later; forehead and upper-eyelid sites carry additional risk.

Naevus sebaceous

A yellow-orange hairless velvety plaque, usually scalp or face, thickens around puberty; a new focal tumour or ulcer should be assessed rather than assuming routine maturation.

Red flags requiring action

New firmness, disproportionate growth, persistent ulceration, bleeding or pain in a congenital naevus; multiple or very large naevi with neurological symptoms; a segmental forehead or eyelid capillary malformation; or a birthmark associated with seizures, weakness, glaucoma symptoms, developmental change or a new mass warrants prompt specialist review.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Structured baseline examinationFirst step
Why
Classify the lesion and find extracutaneous clues that alter urgency.
Interpretation and limitations
Measure two perpendicular diameters, map satellites, palpate nodules, test blanching, examine scalp, eyes and full skin and record neurological, developmental and family findings.
02
Standardised clinical photography
Why
Create a reproducible record of proportional growth and surface change.
Interpretation and limitations
Obtain explicit consent, include a ruler and anatomical overview, use comparable light and angle, label date and site and store only in the approved health record.
03
Dermoscopy
Why
Characterise melanocytic architecture and select a changing focus for sampling.
Interpretation and limitations
Interpret paediatric patterns longitudinally because childhood naevi evolve; dermoscopy cannot safely overrule persistent nodularity, ulceration or bleeding.
04
MRI brain and spine
Why
Assess neurocutaneous melanocytosis in selected children with large or multiple congenital melanocytic naevi or neurological signs.
Interpretation and limitations
Specialists determine indication and timing from projected size, posterior axial distribution, satellite number and symptoms; a normal scan does not remove lifelong clinical vigilance.
05
Ophthalmic assessment
Why
Detect glaucoma or ocular vascular involvement when a capillary malformation affects the forehead or eyelid.
Interpretation and limitations
Early examination includes age-appropriate intraocular-pressure and optic-nerve assessment; repeat surveillance follows the ophthalmic risk plan because glaucoma can appear later.
06
Targeted biopsy
Why
Diagnose a suspicious nodule, ulcer, evolving naevus-sebaceous tumour or uncertain lesion.
Interpretation and limitations
Sample the most concerning representative focus after dermatology and pathology discussion; document prior change and recognise that a benign sampled area does not explain a separate evolving focus.
07
Clinical-genetics assessment
Why
Investigate multiple pigmentary marks or a birthmark with neurological, skeletal, vascular or developmental features.
Interpretation and limitations
Construct a three-generation pedigree and select testing from the phenotype; negative blood testing may not exclude post-zygotic mosaic disease confined to affected tissue.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Infantile haemangioma

Often absent or faint at birth then proliferates rapidly in early weeks, unlike a capillary malformation that is fully present and grows proportionately.

Acquired melanocytic naevus

Appears after infancy and is usually small; history and early records distinguish it from a congenital lesion first noticed late.

Bruising

Changes colour and resolves over days and may be tender or swollen, whereas congenital dermal melanocytosis is stable, flat and documented from early life.

Café-au-lait macule

Uniform flat pigmentation without hair or nodularity differs from many congenital melanocytic naevi and prompts syndromic assessment when multiple.

Epidermal or sebaceous naevus

Linear or yellow-orange textured plaques follow epidermal patterns and have different tumour and syndrome associations from melanocytic lesions.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01First-line classificationName the tissue and map the riskFirst stepFirst lineA congenital or early-life mark is seen without acute illness.

1Confirm timing and growth, inspect and palpate the whole lesion, test blanching, measure it and look for satellites and other cutaneous markers.
2Complete an age-appropriate eye, neurological, developmental and musculoskeletal screen and ask about seizures, headache, vision, weakness and family history.
3Create a consented baseline image and place the lesion into routine reassurance, planned surveillance or urgent specialist assessment according to function and red flags.

02CMN surveillanceTrack proportionate growth and focal changeA congenital melanocytic naevus is clinically stable.

1Record projected adult size category, anatomical site, hair, nodules and satellite number and provide a clear description of changes that should trigger earlier contact.
2Refer large, multiple, difficult-to-monitor or psychosocially burdensome naevi to a specialist team for dermoscopy and consideration of neuroimaging and surgical options.
3Review excision as a function, symptom and preference decision, explaining scar and anaesthetic burden and that surgery does not guarantee removal of melanoma risk.

03Neuro-ocular routeEscalate syndromic distribution earlyEscalationThere are multiple café-au-lait macules, a high-risk capillary-malformation site, numerous CMN satellites or neurological or ocular features.

1Arrange paediatric and relevant dermatology, ophthalmology, neurology or genetics review rather than ordering an undirected panel of scans and genes.
2Use syndrome-specific examination and testing, including eye-pressure assessment or specialist-selected MRI, while treating seizures or acute visual symptoms immediately.
3Give the family one coordinated surveillance plan covering development, vision, blood pressure, neurology, skin change and the professional responsible for each result.

04Suspected malignancySample the changing focusA birthmark develops persistent hard nodularity, ulceration, bleeding, pain, disproportionate growth or nodes.

1Compare with baseline records, examine regional nodes and urgently refer through dermatology or the appropriate suspected-cancer pathway.
2Agree biopsy site and technique with the specialist so viable representative tissue reaches an experienced dermatopathologist with photographs and clinical history.
3Do not reassure solely because the lesion is congenital or because a different nodule was previously benign; maintain safety-net follow-up until pathology and clinic findings agree.

Key medicines and prescribing safety2 treatments · regimens, roles and cautions

Supports dermoscopy-assisted biopsy, small excision or laser-related procedures within a child-centred analgesia plan.

Local anaesthetic for selected procedures

Use an age- and product-appropriate topical or infiltrated local anaesthetic regimen determined by the procedural team; calculate maximum dose by weight and record the total delivered.

Do not apply unmeasured product across a large birthmark or broken skin. Consider distress, procedural sedation needs, allergy and systemic toxicity, and never let anaesthesia planning delay biopsy of a malignant-appearing focus.

Makes clear that surveillance and selected procedural treatment, not unproven creams, address clinically important risk.

No routine preventive medicine

There is no topical or systemic medicine that removes melanoma, glaucoma or neurocutaneous risk from a congenital naevus or capillary malformation.

Avoid bleaching products, corrosive remedies and unsupervised topical treatment; manage eczema, ulceration or infection separately without obscuring a changing lesion before assessment.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Melanoma

Risk is concentrated in larger and more complex CMN phenotypes but suspicious change in any lesion requires assessment rather than reliance on population risk alone.

Neurocutaneous melanocytosis

Central melanocytic deposits may cause seizures, hydrocephalus, focal signs and developmental difficulty and can occasionally undergo malignant change.

Glaucoma and neurological disease

A facial capillary malformation in a high-risk distribution can associate with ocular hypertension and leptomeningeal vascular malformation.

Bleeding, ulceration and friction

Raised or hairy lesions can catch on clothing, while vascular lesions may bleed after trauma or later nodular change.

Psychosocial burden

Visibility, repeated photography, procedures, unwanted questions and bullying can affect autonomy, school participation, body image and family wellbeing.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Give families a body map and a specific route for new lump, growth, ulceration, bleeding, pain, seizure, headache, weakness or visual change rather than relying on a generic annual appointment.
Compare size with overall body growth and palpate the lesion at each relevant review; colour alone varies with light, tanning and skin tone and is an unreliable isolated measure.
For larger or multiple congenital melanocytic naevi, coordinate skin, neurological and developmental follow-up and confirm every requested scan or biopsy has a named reviewer.
For a forehead or eyelid capillary malformation, ensure ophthalmic review continues for the period specified even when the initial eye examination is normal.
Revisit teasing, body image, hair, itching, clothing friction and family treatment priorities, offering psychology, school or peer support without framing visible difference as pathology.
Review consent for serial photography as the child matures and restrict intimate images to the minimum necessary clinical field and secure approved record.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Congenital does not mean static

Many naevi grow proportionately and thicken with age, but focal hardness, ulceration or growth that departs from the child's growth curve is clinically different.

Excision cannot erase remote cells

Melanocytes may remain deep or outside the visible lesion, including the central nervous system, so surgery cannot promise zero melanoma risk.

Blue-grey is not automatically bruising

Congenital dermal melanocytosis has characteristic flat distribution and persistence; early neutral documentation protects children and families from later misinterpretation.

Forehead location predicts more than colour

A capillary malformation involving forehead or upper eyelid has neuro-ocular implications even when it is cosmetically subtle in darker skin.

A normal early test has boundaries

Normal imaging or eye pressure answers the question at that time but does not abolish later glaucoma, evolving phenotype or new-lesion review.

Visibility is a patient-defined burden

Treatment discussion should include function and the child's own experience, not assume that a visible mark requires concealment or correction.

11Common pitfallsFrequent interpretation and management errors.

01
Labelling every blue-grey infant mark a bruise or every brown mark a congenital melanocytic naevus without examining texture, blanching and evolution.
02
Offering prophylactic excision as a guarantee against melanoma.
03
Using an old photograph without scale, consent or comparable lighting as the only surveillance method.
04
Missing glaucoma and neurological risk in a forehead or upper-eyelid capillary malformation.
05
Ordering broad genetic testing without phenotype, pedigree or consent for family and mosaic findings.
06
Dismissing a new hard, ulcerated or bleeding focus because benign nodules can occur in congenital naevi.
07
Talking only to caregivers about an appearance-altering intervention when the child can contribute preferences and assent.