1 Dear readers,

2 Are you ready to brush up your dermatological English? It is our very great pleasure to present the twenty-third English corner based on the giant congenital melanocytic nevus (GCMN). Don’t forget you can use a dictionary to help you with the text, and of course, you should visit our website at http://anglaismedical.u-bourgogne.fr/ to work on your pronunciation or build your medical vocabulary. The site also includes a talking dictionary, medical videos, exercises, clinical cases, words and expressions for specialists…

3 Agiant congenital melanocytic nevus (GCMN) is a dark-coloured patch of skin¹ that is present at birth² and gets larger as the child grows older. It affects roughly³ one in 20,000 infants⁴ worldwide⁵. It frequently occurs on the trunk⁶ or limbs⁷, hence⁸ the name bathing trunk⁹ nevus. The nevus is considered giant if it is more than 20cm in diameter by adulthood. These giant nevi can occur in people of any racial or ethnic background¹⁰ and on any area of the body; they are often hairy¹¹. GCMN is generally not inherited but arises from¹² a somatic (post-conception) mutation in the body's cells leading to¹³ excessive growth of melanocytes, the cells in the skin that are responsible for skin colour. People with giant congenital nevi may have no other symptoms or may have several symptoms such as fragile, dry, or itchy skin. In about 5% to 10% of cases, the giant congenital nevus is associated with neurocutaneous melanocytosis, which means excess pigment cells in the brain or spinal cord¹⁴. These cells may be spread out¹⁵ or grouped together in clusters¹⁶. Their growth can cause increased pressure in the brain, leading to headache, vomiting, irritability, seizures¹⁷, and movement problems. GCMN is also associated with an increased risk of developing malignant melanoma, especially if the nevus is sited¹⁸ on the vertebral column or when there are numerous associated lesions (satellites).

4 Treatment for GCMN depends on the age of the affected individual as well as the size¹⁹, location, and thickness²⁰ of the nevus.

5 The treatment consists mainly of surgery to remove²¹ the nevus. When this is not possible, other treatments, including dermabrasion, chemical peels, ablative laser therapy, curettage or facial excision can be used. In most cases, when there are no neurological problems, the prognosis is good, but the lesions must be examined regularly to look for signs of benign or malignant tumours.

6 Surgery is particularly recommended if there is any likelihood²² that the GCMN may develop into a melanoma. When small nevi are removed, the surrounding skin can often be pulled together with stitches²³. Larger nevi may need to be removed in several stages²⁴ and full-thickness skin grafts may be needed to help the skin heal²⁵ following surgery.

7 Procedures such as dermabrasion and laser therapy may be used to lighten²⁶ the skin or remove hair, but they cannot completely remove the nevus and the effects may only be temporary.

8 Concerning the genetic aspects, mutations in the NRAS gene cause most cases of GCMN. In rare cases, mutations in the BRAF gene cause this condition. Somatic NRAS or BRAF gene mutations cause the altered²⁷ protein in affected cells to be permanently turned on²⁸. The overactive protein may allow cells that develop into melanocytes to grow and divide uncontrollably thus causing GCMN. A somatic mutation in one copy of the NRAS or BRAF gene is sufficient to cause this disorder.

Exercice 1. Trouver la forme complète des acronymes suivants fréquemment utilisés en dermatology :

9 Ex. GCMN → Giant congenital malanocytic nevus

Exercice 2. Trouver le pluriel irrégulier des noms suivants :

11 Ex. nevus → nevi prognosis → prognoses