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Editor,—Acute retinal necrosis (ARN) is a rapidly progressing, sometimes devastating, retinitis associated with the herpes virus family. First described in 1971,1 it is diagnosed by the clinical triad of progressive peripheral retinal necrosis, occlusive vasculopathy, and vitreous inflammation.2 The association of herpetic encephalitis with ARN has been described in adults.34 Herpes simplex virus type 2 (HSV-2) has also been recognised as one of the causative agents of the ARN syndrome, particularly in Japan.5 It has been suggested that ARN in patients less than 25 years of age is likely to be caused by HSV-2.6 We present a case of bilateral ARN (BARN) in a neonate with HSV-2 encephalitis.
A 25 day old infant presented with a 4 day history of lethargy, poor feeding, and coughing. Examination revealed an injected, blistered pharynx and a solitary red skin lesion on the left upper arm accompanied by a cluster of blisters. A clinical diagnosis of possible viral encephalitis was made, and intravenous aciclovir and cefotaxime were commenced. Computed tomography of the brain showed an area of necrosis in the right thalamus. A scrape from the skin lesion and a sample of cerebrospinal fluid (CSF), obtained by lumbar puncture, were sent for polymerase chain reaction (PCR) analysis. Both specimens were positive for HSV-2. HSV-2 was also isolated in tissue culture from a throat swab. Two days later a bilateral retinitis affecting the superior retina in the right eye and the superonasal retina in the left was identified. A small area of retinal detachment subsequently developed outside the vascular arcades superiorly in the right eye. While in the left eye, an extensive superior retinal detachment occurred, threatening the macula; in the right eye indirect argon laser photocoagulation was used to demarcate the interface between necrotic and healthy retina (Fig 1). In the left, laser was not applied because of the proximity of subretinal fluid to the macula. After 4 days the retinitis was inactive in both eyes; however, a week later the right retina became necrotic posterior to the original laser treatment and further indirect laser was applied. In the left eye massive subretinal haemorrhage involving the macula developed and the child underwent left pars plana vitrectomy, vitreous and retinal biopsy, posterior hyaloid peel, endolaser, air/fluid exchange, and silicone oil tamponade. Analysis of the vitreous sample revealed a non-diagnostic band on PCR. Histology, including electron microscopy, of the retinal biopsy showed only necrotic tissue.
The fundal appearance stabilised and oral aciclovir was commenced which has been maintained to date. A maternal blood sample taken during the second trimester of pregnancy was retrospectively analysed and found to be negative for HSV-2. A sample obtained 2 months post partum was positive for HSV-2.
Neonatal HSV infection is usually symptomatic and has a high mortality. Three quarters of cases are due to HSV-2 and this is most commonly acquired from the maternal genital tract lesion during delivery.7 The maternal HSV titres in this case suggest that the mother acquired a primary infection during the third trimester. A diagnosis of encephalitis was confirmed by the CT scan appearance and a PCR positive for HVS-2 in the CSF. The retinitis was first observed only 6 days after the onset of the systemic symptoms and progressed significantly despite intravenous administration of aciclovir. This treatment was continued for several weeks and was then followed by oral therapy. The fact that HSV was not identified from the vitreous or retinal biopsy may be attributable to the prolonged antiviral treatment.8
HSV encephalitis is a severe infection, especially in the neonate, that carries a potential risk of significant ocular involvement. This case highlights the importance of early diagnosis and active management. Like ARN in adults, this may include the need for prophylactic laser retinal photocoagulation to prevent retinal detachment9and, should this fail, pars plana vitrectomy with silicone oil tamponade.10