Infantile haemangiomas do not occur more frequently in children with congenital melanocytic naevi

DEAR EDITOR, Infantile haemangioma (IH) is a very common benign vascular tumour with a reported incidence of 4–10% in infants, and no clear genetic basis described as yet. Congenital melanocytic naevi (CMN) are benign melanocytic tumours present in 1% of newborns, which when multiple are caused by post-zygotic mutations in the gene NRAS in the majority of cases, and when single, carry various somatic mutations where causality is difficult to prove. Melanocytic and vascular anomalies can coexist in the condition phakomatosis pigmentovascularis (PPV), and the same genetic mutation is responsible for both cutaneous lesions; however, these do not involve either CMN or IH. Moreover, the vascular lesion in PPV is considered congenital and malformative as CMN, and not proliferative and acquired as IH. A case series of six patients presenting with both CMN and IH has been reported previously, where the authors hypothesized that this co-occurrence might be more common than expected by chance. To test this hypothesis we conducted a systematic evaluation of the presence of IH in the cohort of patients with CMN seen in our tertiary referral service over a 10-year period between March 2006 and February 2016. All children were examined by the same physician, and data were collected prospectively. We included in this analysis only children less than 3 years of age at the examination date, as the natural history of IH is to spontaneously involute during the first few years of life. A total of 244 patients with CMN under the age of 3 years were seen in this time period, with a mean and median age of 0 78 years and 0 53 years, respectively. Of these, 142 were females, giving the same male : female ratio of 1 : 1 4 as has previously been reported for our CMN cohort. Fourteen patients were recorded as having an IH (5 7%), compatible with prevalence figures for the general population. Furthermore, the characteristics of those with an IH mirror those of the general population, as the male : female ratio for those with IH and CMN was 1 : 6. Table 1 shows the clinical characteristics of the patient cohort, comparing those with and without IH. The number of patients with CMN and IH is too small to perform a statistical comparison of the severity of CMN phenotype, but clinical phenotyping data are shown in Table 1. This systematic study of the prevalence of IH in a cohort of patients with CMN has found no increase above that of the normal population, and a sex ratio in line with what we would expect for IH alone. This study does not support a connection at a genetic level between CMN and IH, either at germline predisposition or at somatic mutation level.