Spontaneous central retinal artery occlusion in a teenager with sickle cell trait.

Sickle cell trait (SCT) is traditionally considered a benign condition by ophthalmologists. Several studies have reported ocular complications in SCT, but these complications have been described as a consequence of trauma, exertion, and associated systemic disorders. We here in the report a case of an Arab teen boy, who presented with a sudden loss of vision in his left eye of 1 h duration. The ocular examination revealed acute central retinal artery occlusion. He underwent a series of laboratory and radiological investigations. The blood investigations revealed SCT and abnormal partial thromboplastin time. The fundus fluorescein angiography revealed abnormal retinal vascular perfusion. Marked blood rheological impairment and activation of the coagulation pathway can occur without any contributing factors in SCT leading to severe ocular complications. This is one of the young patients with spontaneous vascular occlusion in SCT.

INTRODUCTION

Sickle cell trait (SCT) is traditionally considered a benign condition by ophthalmologists.1 Several studies have reported ocular complications in SCT, but these complications have been described as the consequence of trauma,2 exertion,3 and associated systemic disorders.4 This case report describes an unusual occurrence of spontaneous central retinal artery occlusion in a teenage boy with SCT. This article also highlights that marked blood rheological impairment and activation of the coagulation pathway that can occur in SCT without any precipitating cause and can lead to potential blinding ocular complications without other risk factors.

CASE REPORT

A 14-year-old Arab Asian boy, presented to Dubai Hospital emergency with a sudden loss of vision in left eye of 1 h duration. He was on a short visit to emirates. He did not give a history of trauma, exercise or any systemic illness proceeding to visual loss. There was no known hematological abnormality in the family. On clinical examination, vision in the left eye vision was only perception of light and intraocular pressure was 14 mmHg. Anterior segment examination showed relative afferent papillary defect, clear and quiet anterior chamber. Fundus examination showed clear vitreous, mild hyperemic optic disc with few flame shaped hemorrhages. Posterior pole showed opaque retinal edema with cherry red spot. There was mild dilatation of veins with box-carrying of the flow in nasal vessels. There were few peripheral retinal hemorrhages. Fundus photograph after 1 week showing whitish-yellow appearance of the posterior pole with macular edema [Figure 1]. Right eye vision was 20/20. Anterior segment and fundus examination were unremarkable. He was treated with immediate ocular massage, anterior chamber paracentesis and topical timolol maleate 0.5% eye drops instillation. He underwent laboratory blood investigations, carotid Doppler, magnetic resonance imaging brain with orbits, fundus fluorescein angiography (FA), optical coherence tomography, chest X-ray and cardiac evaluation (echocardiography and electrocardiography).

Figure 1

Fundus photograph after 1 week showing whitish yellow appearance of the posterior pole with macular edema

All the investigations were within normal limits except hemoglobin electrophoresis and partial thromboplastin time (PTT). Hemoglobin electrophoresis showed, SCT: HBA - 58%, HBA2 - 3.86 (range: 1.5-3.5), HBS - 38.23%, PTT - 46 s (range 28-41 s). Over the ensuing week, there was no improvement in his vision. At this stage, fundus examination revealed opaque macular edema. FA frames of left eye (After 10 s of injection of dye), during the early arteriovenous (A-V) phase shows normal filling of the retinal arterioles with patchy choroidal fluorescence [Figure 2a]. Figure 2b showing complete filling of arterioles with lamellar flow of dye in the veins. There is absence of fluorescence in the macular region, corresponding to the area with most marked retinal swelling. Temporal arcades still showing lamellar flow of fluorescence in the veins and hypo-fluorescence at the macula [Figure 2c]. Figure 2d shows complete filling of arterioles and veins. A-V transit time was increased (25 s). There was persistent absence of fluorescence at macula due to obliteration of vessels. FA late frames of the periphery of temporal, nasal and superior quadrants respectively showing complete vascular filling defects. There are focal areas of blocked fluorescence in the temporal quadrant corresponding to the area of retinal hemorrhages [Figure 3a–d]. FA of right eye showing normal study [Figure 4a]. FA frame 5 min after injection of the dye still shows complete absence of filling in the macular region and faint perivascular and optic disc leak [Figure 4b]. Further follow-up of this patient was not possible since patient went back to his native country.

Figure 2

(a) Fluorescein angiography frames of left eye (10 s after injection), during the early arteriovenous (A-V) phase shows normal filling of the retinal arterioles. (b) Complete filling of arterioles with lamellar flow of dye in the veins. There is hypo-fluorescence in the macular region, corresponding to the area with most marked retinal swelling. (c) Temporal arcades still showing lamellar flow in veins. (d) Complete filling of arterioles and veins. A-V transit time was increased (25 s). There was persistent absence of fluorescence at macula due to obliteration of vessels

Figure 3

(a-d) Fluorescein angiography late frames of the periphery of temporal, nasal, and superior quadrants respectively showing complete vascular filling defects. There are focal areas of blocked fluorescence in the temporal quadrant corresponding to the area of retinal hemorrhages

Figure 4

(a) Fluorescein angiography (FA) of right eye showing normal study. (b) FA frame 5 min after injection of the dye still shows complete absence of filling in the macular region and faint perivascular and optic disc leak

DISCUSSION

Sickle cell trait (also known as being a carrier) occurs when a person has one gene for sickle hemoglobin and one gene for normal hemoglobin. Approximately 1 in 10 African-Americans carries SCT. It is known that people who are carriers generally do not have any medical problems. Recent studies have shown that SCT is probably associated with complicated hyphema, venous thromboembolic events, fetal loss, neonatal deaths, and preeclampsia, and possibly associated with acute chest syndrome, asymptomatic bacteriuria, and anemia in pregnancy.5 Unilateral central retinal artery occlusion has been reported in sickle cell hemoglobinopathes6(i.e. SS, S-thal, sickle trait, and sickle cell), but the association with SCT with no precipitating factors is rare. Most reports have described additional contributing factors, such as trauma2 or concomitant systemic illness,4 to account for the central retinal artery occlusion. The risk of vascular collapse occurs with extreme exercise particularly in association with heat, altitude, hypoxia, and dehydration. Under these extreme conditions SCT cells may “sickle” or polymerize transforming silent SCT into a syndrome with risk of organ damage from vaso-occlusion crises. Therefore, the clinical consequences of SCT are rare and unpredictable or probably genetically predetermined.

This case report of spontaneous central retinal artery occlusion (CRAO) in a SCT suggests that, marked blood rheological impairment and activation of the coagulation pathway can occur without any precipitating cause. The presence of superficial retinal hemorrhages also suggests concomitant venous occlusion in this case. Therefore, SCT could be considered as a risk factor for significant ocular complications even without contributing factors. The need for close observation under retina specialist care was explained to our patient since there was a risk of development of ocular neovascularization and its complications. Peripheral laser photocoagulation ablating the peripheral ischemic areas could probably prevent severe complications although the visual prognosis was poor in this case. The present report is one of the young patients with CRAO with SCT and only case reported in the literature so far, where there is spontaneous CRAO leading to severe blindness in SCT.