CMV is the most common congenital and perinatal viral infection and the fetus may become infected as a consequence of primary and recurrent maternal infections [
2]. Five percent of all congenitally infected children have severe disease, another 5 % have mild involvement, and 90 % are born with subclinical but chronic CMV infections [
4]. Long-term sequelae occur in 40–58 % of symptomatic children and in 13.5 % of asymptomatic children at birth [
4]. The most characteristic neurological problems include a mild increase in cerebrospinal fluid protein, sensorineural hearing loss and chorioretinitis. Active CMV infection is confirmed by virus isolation from the urine, saliva, washings, breast milk, cervical secretions and tissues obtained by biopsy using PCR for the detection of CMV-DNA. CMV retinitis is known to occur in immunosuppressed individuals, and its incidence has increased over the last few years as a result of acquired immunodeficiency syndrome (AIDS) [
5]. However, congenital CMV infection-associated retinitis may occur in patients with no systemic immune dysfunction [
6]. The present patient was referred to us at 1 day of age, and he showed remarkable dilation of the retinal vessels and arterio-venous anastomoses in both eyes associated with congenital symptomatic CMV infection. Although the extent of immunosuppression was not determined, the diagnosis was made by clinical findings and cultures of blood and urine, from which the virus was isolated. These findings strongly suggested an active, systemic CMV infection. However, retinal arterio-venous anastomosis has not been previously described in conjunction with congenital CMV infection [
7] except for one German article that reported aplasia of retinal vessels in a patient with congenital CMV infection [
8]. As a differential diagnosis, we considered ROP due to FGR. However, it is unlikely that retinal vessel abnormalities due to ROP would promptly regress in a few days with only oral valgancyclovir. The present case showed retinal vessel abnormalities at 1 day of age after 36 weeks’ gestation. A previous report demonstrated severe retinitis and optic neuritis at 1 day of age in an infant born at 35 weeks’ gestation weighing 1180 g [
9]. Interestingly, rapid and dramatic improvement of retinitis and optic neuritis was observed three days after an intravitreal injection of ganciclovir in that case; a similar rapid improvement was found in the present case. Therefore, we speculated that the fundus manifestations might be affected by the underlying state (including duration) of the ocular CMV infection although the details remain unclear. However, it is possible that our case also had mild retinitis and optic neuritis since chorioretinal atrophy at the macula and around the optic disc was subsequently found at three months of age. The mechanism describing how CMV influences retinal vascular structure is largely unknown, but previous studies showed that CMV induces proinflammatory and angiogenic cytokines in retinal pericytes [
10,
11] and induces an anti-migratory and anti-angiogenic endothelial cell phenotype. These two changes could have a detrimental effect on vasculature development.