Neurocutaneous melanosis: Criteria for diagnosis

Sir, We read with great interest the case report by Ahuja et al of a child, 6 weeks old, with multiple giant congenital melanocytic nevi and central nervous system melanosis. Neurocutaneous melanosis has been reported to manifest itself most commonly within the first two years of life and children with this entity have been born as still births or have been reported at as early as one month of age. However we agree that such a young age has not been probably reported before in Indian literature. We are very impressed at the fact that the authors suspected the entity of neurocutaneous melanosis in view of the fact that the child had multiple giant nevi located on the scalp, neck and posterior axilla (which are said to be risk factors for CNS melanosis) and proceeded to a MRI of the brain even though the baby was neurologically normal. However, if one goes through the two landmark articles on this entity by Kadonaga et al and Fox et al one would come to the conclusion that this case reported would only qualify as a ‘provisional’ case of neurocutaneous melanosis. Both Fox and Kadonaga have laid down criteria for the diagnosis of neurocutaneous melanosis which are as follows : 1. Unduly large or unusually numerous pigmented cutaneous nevi in association with CNS melanosis or melanoma. This patient qualified this criteria. 2. No incidence of malignant change in any of the cutaneous lesions, except in patients in whom the examined areas of the CNS lesions are histologically benign. This criteria is very important because a significant percentage of patients with large congenital melanocytic nevi develop cutaneous melanoma and when cutaneous melanoma is present, the estimated incidence of CNS metastases is about 40%. Therefore if the CNS lesions have not been proved to be benign the cutaneous lesions have to be proved benign to rule out the possibility of the CNS lesions arising just out of metastases from a cutaneous melanoma. Letter to Editor