Giant Congenital Melanocytic Nevus

National Organization for Rare Disorders, Inc.

Important
It is possible that the main title of the report Giant Congenital Melanocytic Nevus is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.

Synonyms

  • bathing trunk nevus
  • cape nevus
  • congenital pigmented nevus
  • garment nevus
  • giant brown birthmark
  • giant hairy nevus
  • giant hairy pigmented nevus
  • giant mole
  • giant nevus
  • hairy birthmark
  • leptomeningeal melanosis
  • multiple congenital melanocytic nevi
  • neurocutaneous melanocytosis
  • neurocutaneous melanosis
  • satellite nevi
  • swimming trunk nevus

Disorder Subdivisions

  • None

General Discussion

Summary
Congenital melanocytic nevi (CMN) are visible pigmented (melanocytic) proliferations in the skin that are present at birth. CMN are benign, tumor-like malformations resulting from faulty development of pigment cell (melanocyte) precursors in the embryo, and composed of an abnormal mixture of skin elements. Defined areas of these melanocytic proliferations cover surfaces at the base of the epidermis ranging from a few millimeters in diameter to large sectors of the body. In the larger forms, the CMN (single or multiple) also extend(s) vertically into the deeper dermis and more rarely, into the hypodermis or even subcutaneous tissues. The most superficial component of the CMN is the most highly pigmented, conferring brown-to-black shades to the overlying epidermis. CMN are usually classified according to their predicted largest diameter in adulthood, as if they were circular (predicted adult diameter or PAS). The most used classification assigns small CMN as less than 1.5 cm PAS, medium sized CMN between 1.5 to 19.9 cm, and large CMN 20 cm or greater. CMN measuring 50 cm or larger in PAS have been referred to as ‘giant congenital melanocytic nevi'.

CMN can be light brown to black patches or plaques, can present in variable ways, and cover nearly any size surface area or any part of the body. The incidence of CMN seems to be independent of skin color or other ethnic factors. Small to medium CMN are predicted to occur in more than one in a hundred births. Large and especially giant CMN, exceeding a predicted diameter at adult age of at least 20 cm on the body, form a much rarer subset, with prevalence estimated at around 1 in 50,000 births. Non-pigmented or small incipient congenital lesions can also be present - these are known as "tardive"; the emergence of so-called "satellite" nevi throughout the first few years of life in conjunction with larger CMN probably reflects the postnatal maturation of such precursors. On occasion, even a primary CMN can appear in a tardive manner. Treatment options currently are exclusively surgical. Neurocutaneous melanocytosis, cited in earlier literature as neurocutaneous melanosis (NCM), is a neurological and cutaneous disorder characterized by abnormal aggregations of nevomelanocytes within the central nervous system and the skin. NCM is a complication of the larger forms of CMN, or multiple smaller CMN, in a fraction of patients. Recent studies find the incidence of symptomatic and asymptomatic NCM together to range between 5 and 15 % of all persons with large and giant CMN. Melanoma develops in an estimated 1-2% of patients with LCMN or NCM, more frequently and at earlier ages than in the general population.

Introduction
The first recorded descriptions of children with large CMN date from observations published by the Count of Buffon before the French Revolution. Other giant, sometimes rugous CMN were described in the early 19th century.

CMN tend to grow in a proportional fashion to the child's growth; occasionally growth appears out of proportion to the child during periods of particularly rapid growth such as early infancy. A new size/color/texture classification, recently developed by Marghoob, Krengel and other experts in the field, may eventually help in better predicting patients at the greatest risk for developing melanoma or neurological disease by more reproducibly classifying similar patients. Nomograms can assist clinicians in easily determining the PAS of a nevus examined at any point during childhood.

Resources

Nevus Network
PO Box 305
West Salem, NC 44287
USA
Tel: (419)853-4525
Fax: (405)377-3403
Email: info@nevusnetwork.org
Internet: http://www.nevusnetwork.org/

Nevus Outreach, Inc.
600 SE Delaware Ave., Suite 200
Bartlesville, OK 74003
USA
Tel: (918)331-0595
Fax: (281)417-4020
Tel: (877)426-3887
Email: mbeckwith@nevus.org
Internet: http://www.nevus.org

For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders (NORD). A copy of the complete report can be downloaded free from the NORD website for registered users. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational therapies (if available), and references from medical literature. For a full-text version of this topic, go to www.rarediseases.org and click on Rare Disease Database under "Rare Disease Information".

The information provided in this report is not intended for diagnostic purposes. It is provided for informational purposes only. NORD recommends that affected individuals seek the advice or counsel of their own personal physicians.

It is possible that the title of this topic is not the name you selected. Please check the Synonyms listing to find the alternate name(s) and Disorder Subdivision(s) covered by this report

This disease entry is based upon medical information available through the date at the end of the topic. Since NORD's resources are limited, it is not possible to keep every entry in the Rare Disease Database completely current and accurate. Please check with the agencies listed in the Resources section for the most current information about this disorder.

For additional information and assistance about rare disorders, please contact the National Organization for Rare Disorders at P.O. Box 1968, Danbury, CT 06813-1968; phone (203) 744-0100; web site www.rarediseases.org or email orphan@rarediseases.org

Last Updated:  2/14/2013
Copyright  2013 National Organization for Rare Disorders, Inc.

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