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Start free with EleplanLarge/giant congenital melanocytic nevus
ORPHA:626Disease
Also called LGCMN · Large/giant CMN syndrome · Large/giant congenital pigmented nevus
What it is
A rare skin hamartoma characterized by at least one pigmented skin lesion present at birth of more than 20 cm (large congenital melanocytic nevus; LCMN) or 40 cm (giant; GCMN) projected adult diameter. The primary lesion is composed of mutated melanocytes and often locally disorganized epidermal annexes or dermis, and presents with an elevated risk of malignant transformation to melanoma or, more rarely, other neoplasms in skin or central nervous system.
Key facts
- Prevalence
- 1-9 / 100 000 (Europe)
- Age of onset
- Infancy, Neonatal
- Inheritance
- Multigenic/multifactorial
- Classified as
- Disease
Prevalence figures describe populations, not individuals, and are often estimates from a single study. Where the figure is an incidence or a birth prevalence, it says so.
Signs and symptoms
Sometimes5–29%
12- Atypical behavior
- Cutaneous melanoma
- Headache
- Hydrocephalus
- Hypertrichosis
- Hypopigmented skin patches
- Increased intracranial pressure
- Neurodevelopmental delay
and 4 more in this range
These ranges are how often a sign appears across everyone diagnosed, not a prediction for one person — most people have some of these and not others. Orphanet also records findings that are specifically absent in this disease; those are in the data but not listed here.
Genes
ICD-10 codes
Related health topics
Reached through the ICD-10 categories this disease is filed under, so these describe the broader group rather than this disease specifically.
Cross-references
Orphadata Science: Free access data from Orphanet. © INSERM 1999. Data version 2026-06-23. Available under CC BY 4.0. This is a reference, not medical advice.
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