Bilateral persistent hyperplastic primary vitreous.

A case of bilateral persistent hyperplastic primary vitreous (PHPV) in a 3-month-old male infant, who had bilateral leukokoria, is presented. The child was referred for imaging with a clinical suspicion of retinoblastoma. Gray-scale ultrasound evaluation revealed an echogenic band in the posterior segment of both globes, extending from the posterior surface of the lens capsule to the optic disc. Doppler examination revealed the presence of arterial flow in the band in both globes. Associated echogenic hemorrhage was also seen, which was confirmed by computed tomography. Most cases of PHPV are sporadic and unilateral, and bilateral PHPV is rare. The imaging features in this case suggest the diagnosis of bilateral PHPV and differentiate it from retinoblastoma. This entity, although infrequent, should be considered in the differential diagnosis while evaluating bilateral leukokoria.

Persistent hyperplastic primary vitreous (PHPV) is an uncommon condition, presenting clinically as leukokoria (white pupillary reflex), micro-ophthalmia, and cataract. Bilateral PHPV is rare. Most important differential diagnosis is retinoblastoma, which can be differentiated by imaging features.

Case Report

A 3-month-old male infant presented with bilateral leukokoria. Birth history of the child was unremarkable. On initial examination, the size of the cornea looked smaller. The child was referred for ocular ultrasound examination, with a clinical suspicion of retinoblastoma. An ultrasound study was performed with a high-frequency transducer operating at 10 MHz (L5, GE Medical Systems, USA). Gray scale evaluation revealed an echogenic band in the posterior segment of both globes extending from the posterior surface of the lens capsule to the optic disc. The axial length of the globes was 16 mm, which was suggestive of micro-ophthalmia. Color doppler examination revealed the presence of blood flow in the band [Fig. 1A]. Spectral analysis of this blood vessel showed arterial waveforms [Fig. 1B]. Hyperechoic foci were seen in both the posterior segments adjacent to the artery, suggestive of associated vitreous hemorrhage [Fig. 1B]. No calcification was seen.

Figure 1

A 3-month-old infant who presented with bilateral leukokoria. (A) Axial ultrasound image with color Doppler shows a vessel running through the vitreous of both globes, from the posterior surface of the lens capsule to the optic disc (arrowhead). Echogenic foci suggesting hemorrhage are also seen (arrows). (B) On pulsed Doppler examination, the vessel shows arterial flow

Computed tomography (CT) of the orbits (Lightspeed, GE Medical Systems, USA) revealed diffusely hyperdense vitreous in both globes, suggestive of hemorrhage [Fig. 2]. No solid mass or calcification was seen on either side. Subtle linear densities were seen in the vitreous of both globes, representing hyaloid artery in Cloquet's canal [Fig. 2].

Figure 2

A 3-month-old infant who presented with bilateral leukokoria. Axial CT image shows diffusely hyperdense attenuation of vitreous in both globes, suggesting hemorrhage. Subtle linear structures are also seen (arrowheads), representing hyaloid artery in Cloquet's canal

Based on the above findings, the patient was diagnosed with bilateral PHPV. Further investigation failed to reveal any history of similar disorder in the family of the patient. The parents were advised to get him examined under general anesthesia, so that appropriate management could be decided. However, the parents were unwilling for a procedure under anesthesia and refused for the examination. Leukokoria was thought to be due to vitreous hemorrhage.

Discussion

PHPV occurs because of an incomplete regression of the embryonic vitreous and hyaloid vasculature. The primary vitreous is formed during the first month of development and contains branches of the hyaloid artery. This hyaloid artery begins to regress during the formation of the avascular secondary vitreous at 9 weeks. By the third month, the secondary vitreous, which ultimately forms the adult vitreous, fills most of the developing vitreous cavity. The primary vitreous becomes condensed into a narrow band (Cloquet's canal), running from the optic disc to the posterior aspect of the lens.[12] PHPV is classified into three types: anterior, posterior, or a combination of the two.[2]

Bilateral leukokoria in a child may be due to a number of causes, of which retinoblastoma, congenital cataract, retinopathy of prematurity (ROP), severe intermediate uveitis, and retinal dysplasias are the most frequent.[2] PHPV usually presents with unilateral leukokoria.[12] Bilateral PHPV is rare. While analyzing patients presenting with PHPV, Pollard found two of 83 (2.4%) cases to be bilateral,[3] while Haddad et al. found seven of 62 (11%) cases to be bilateral.[4] It is important to exclude retinoblastoma in all cases of leukokoria.

Persistent hyperplastic primary vitreous has a typical imaging appearance, which allows reliable differentiation from retinoblastoma. In PHPV, gray-scale ultrasonography shows an echogenic band extending from the posterior surface of the lens capsule to the optic disc. Doppler may show arterial flow within this band representing a persistent hyaloid artery[2] [Fig. 1].

CT findings of PHPV are absence of calcification, increased density of the entire vitreous, tubular intravitreal density (Cloquet's canal or nonattached retina) [Fig. 2], decubitus positioning showing a gravitational effect on fluid-fluid level, micro-ophthalmia, enhancement of abnormal intravitreal tissue, and small or irregular lens.[1]

Magnetic resonance imaging (MRI) findings of PHPV consist of a tubular structure, representing the hyaloid vessel; a funnel-shaped retinal detachment, with the subretinal fluid hyperintense on both T1- and T2-weighted images; fluid-fluid level due to the presence of hemorrhage in the subretinal space; a retrolental mass; micro-ophthalmia, and vitreous hemorrhage.[5]

PHPV can be differentiated from retinoblastoma by the absence of a calcified mass, artery running through Cloquet's canal, and typical signal characteristics of retinoblastoma on MRI, i.e., hyperintense on T1-weighted images and hypointense on T2-weighted images.[1] A patent hyaloid artery, as noted in this case, is not a feature of vitreoretinal dysplasias.[2] Differentiation from advanced retinopathy of prematurity (ROP) can be difficult on imaging alone. History of a premature, low birth weight infant undergoing prolonged supplemental oxygen therapy helps to distinguish it from bilateral PHPV.[1]

Complications of PHPV include rupture of the lens capsule, cataract formation, intraocular hemorrhage, secondary glaucoma, tractional retinal folds, and subsequent phthisis bulbi. The friability of the hyaloid vasculature predisposes to vitreous hemorrhage, which was noted in both globes in the present case. Majority of patients with posterior PHPV never obtain useful vision.[23]

The imaging features in this case point toward the diagnosis of bilateral PHPV. This entity, although rare, should be considered in the differential diagnosis of retinoblastoma while evaluating bilateral leukokoria.