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Start free with EleplanCongenital smooth muscle hamartoma
ORPHA:263435Disease
What it is
Congenital smooth muscle hamartoma (CSMH) is a rare cutaneous hamartomatous lesion most often located on the lumbosacral area or proximal limbs (but rarely on atypical areas such as scalp, eyelid or foot) and characterized by a disorganized proliferation of smooth muscle fibres of arrector pili presenting usually as a localized skin-colored or hyperpigmented plaque (up to 10 cm in diameter) with prominent vellus hairs (most common classic form) or less commonly by multiple skin-colored papules that can coalesce to form irregularly shaped plaques. With time, hyperpigmentation and vellus hairs usually diminish and neither malignant transformation nor associated systemic involvement has been reported.
Key facts
- Prevalence
- 1-5 / 10 000 (at birth, Israel)
- Age of onset
- Infancy, Neonatal
- Inheritance
- Not applicable
- 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.
ICD-10 codes
ICD-10 has no distinct code for most rare diseases, so many are filed under the nearest available one. A shared code identifies the group, not this disease — the ORPHAcode above is what identifies it.
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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