Monitor patients for melanoma, CNS complications
Patients with CMN are at increased risk of neurocutaneous melanosis (NCM) and cutaneous melanoma.
Neurocutaneous melanosis, a complication of giant congenital nevi, is a melanocyte proliferation in the central nervous system (CNS). Between 6% and 11% of patients with giant congenital nevi develop symptomatic NCM in childhood. Thus, any CNS symptoms should be fully evaluated.4,6 NCM can result in seizures, cranial nerve palsy, hydrocephalus, and leptomeningeal melanoma.
Besides giant congenital nevi, risk factors for NCM include male sex, large numbers of satellite nevi, and the presence of nevi over the posterior midline or head and neck.7 The prognosis is poor for patients who develop neurologic symptoms. NCM is associated with other malignancies, including rhadomyosarcoma, liposarcoma, and malignant peripheral nerve sheath tumors.4
Magnetic resonance imaging (MRI) is helpful to exclude NCM. Ideally, an MRI should be ordered before 4 months of age, at which time myelination begins to make the identification of melanin deposits in the CNS more challenging.7 Not all patients with imaging findings that are consistent with NCM will develop symptoms.8