Activated protein C resistance in patients with central retinal vein occlusion

Pediatric Retinal Detachment in Homozygous Protein C Deficiency: Genetic and Phenotypic Description of a Single Family

Homozygous protein C deficiency is a rare hypercoagulability disorder. This study describes the ocular manifestations and the genetic background in a family with two affected children. This is a retrospective review of ophthalmic examinations, investigations, genetic testing, and blood work-up of two children with homozygous protein C deficiency from a single family. A family with a positive history of consanguineous marriage was found to have two affected children with homozygous protein C deficiency. Abnormal visual behavior was the presenting symptom. Both children had bilateral total tractional retinal detachments at presentation. Skin manifestations included episodes of discoloration and bruising. Laboratory work-up revealed absent protein C activity. Genetic testing confirmed the presence of a homozygous pathogenic mutation in protein C gene (NM_000312.3: c.1297G>A: p.Gly433Ser). Homozygous protein C deficiency should be considered in the differential diagnosis of early-onset tractional retinal detachment in infancy. Although rare, the ophthalmologist may be the first to encounter the condition, and treatment with protein C replacement or anticoagulants may be life-saving. Examination under anesthesia with fluorescein angiography and laser treatment early in life may be warranted to preserve vision. [Ophthalmic Surg Lasers Imaging Retina. 2022;53:293-296.].

Risk Factors in Central Retinal Vein Occlusion and Activated Protein C Resistance

Introduction

Central retinal vein occlusion (CRVO) tends to be a disease of older individuals, with some known major risk factors, and activated protein C resistance seems to be one of the causes in younger patients. In this study, we reviewed risk factors including activated protein C resistance in a series of patients with CRVO.

Methods

Twenty-four patients with a diagnosis of CRVO presenting either acutely or for a follow-up visit during the study period, were enrolled. Ages ranged between 31 and 83 years (mean 59.7). The risk factors, presence of ischemia, the results of biochemical serological and hematological tests, especially activated protein C resistance (APC-R), were analysed.

Results

In 17 patients (71%) one or more of the following risk factors existed: hypertension, diabetes, oral contraceptive usage, family history of thrombosis, and previous operation. In 40% of the eyes, there were ischemic changes. Serum triglycerides were high in 4 of 21 patients (19%) and cholesterol and urea were high in 10 of 21 patients (19%). APC-R was found in 6 out of 24 patients (25%).

Conclusions

Besides known predisposing factors like hypertension, diabetes, glaucoma and hyperlipidemia, APC-R seems to be a risk factor for CRVO at all ages.

Factor V G1691A is associated with an increased risk of retinal vein occlusion: a meta-analysis

We performed a meta-analysis to investigate the association between the Factor V G1691A polymorphism and the risk of retinal vein occlusion (RVO). This analysis included 37 studies involving 2,510 cases and 3,466 controls. Factor V G1691A was associated with an increased risk of RVO in the allele, heterozygote, dominant, and carrier models (PA < 0.001, odds ratios >1), but not the homozygote or recessive models (PA > 0.05). Similar results were observed in a meta-analysis of central retinal vein occlusion (CRVO) and when comparing Caucasian subgroups to population-based controls. These data demonstrate that the G/A genotype of Factor V G1691A is associated with an increased risk of RVO/CRVO in a Caucasian population.

Branch retinal vein occlusion: pathogenesis, visual prognosis, and treatment modalities

In branch retinal vein occlusion (BRVO), abnormal arteriovenous crossing with vein compression, degenerative changes of the vessel wall and abnormal hematological factors constitute the primary mechanism of vessel occlusion. In general, BRVO has a good prognosis: 50-60% of eyes are reported to have a final visual acuity (VA) of 20/40 or better even without treatment. One important prognostic factor for final VA appears to be the initial VA. Grid laser photocoagulation is an established treatment for macular edema in a particular group of patients with BRVO, while promising results for this condition are shown by intravitreal application of steroids or new vascular endothelial growth factor inhibitors. Vitrectomy with or without arteriovenous sheathotomy combined with removal of the internal limiting membrane may improve vision in eyes with macular edema which are unresponsive to or ineligible for laser treatment.

Influence of factor V Leiden on the development of neovascularisation secondary to central retinal vein occlusion

AIMS

To investigate if the presence of factor V Leiden has an influence on the prognosis in central retinal vein occlusion (CRVO).

METHODS

166 patients with CRVO were studied retrospectively. They were tested for factor V Leiden using DNA analysis. The presence of the mutation was studied in correlation with the development of neovascular complications 1 year after the thrombotic event.

RESULTS

56 of 166 patients (34%) developed neovascular complications after 1 year. In the patients who had the studied mutation 11 of 20 (55%) had developed neovascular complications after 1 year, compared to 45 of 146 patients (31%) in the group without factor V Leiden (p=0.04).

CONCLUSION

The presence of factor V Leiden seems to enhance the risk of developing neovascular complications in CRVO.

Central retinal vein occlusion and thrombophilia

Central retinal vein occlusion is one of the commonest vascular diseases of the eye. The pathogenesis is multifactorial with both local factors and systemic diseases being aetiologically important. Many thrombophilic conditions have recently been identified and studies looking at their potential role in CRVO have been undertaken. The aim of this review is to critically appraise these studies as to date many have given conflicting results, making it far from clear what role thrombophilic conditions play in CRVO. It appears that hyperhomocysteinaemia and antiphospholipid syndrome are causes of CRVO and there is evidence that disorders causing hypofibrinolysis may also be important. The common hereditary thrombophilic conditions however do not appear to be strong risk factors but larger studies are needed for a definitive answer.

Is activated factor VII associated with retinal vein occlusion?

AIM

To determine whether a newly identified thrombophilia factor, activated factor VII (FVIIa), is associated with retinal vein occlusion (RVO).

METHODS

54 consecutive cases with RVO seen between March and September 1999 were included in the study. 22 cases had central retinal vein occlusion (CRVO) and 32 had branch retinal vein occlusion (BRVO). Ophthalmoscopic examination with detailed medical history was followed by blood analyses for liver and renal functions, cholesterol, triglycerides, complete blood count, and coagulation factors including protein C activity, free protein S, antithrombin III, fibrinogen, and factor VIIa (FVIIa). Data were compared with those of the control group, composed of 19 cases under ophthalmological follow up for refractive errors, presbyopia, or senile cataract.

RESULTS

Hypertension was highly prevalent in cases with BRVO. Complete blood count, and liver and kidney function tests were within normal limits in the study group. Two cases had low protein C activity, and one had low free protein S. FVIIa levels were significantly higher in the RVO group than in the control group (p=0.0004). There was no significant difference in FVIIa levels between the CRVO and BRVO groups (p=0.51).

CONCLUSION

No haematological parameter except FVIIa differed significantly from that of the control group. Elevation of FVIIa level may play a part in the pathophysiology of both CRVO and BRVO.

Familial thrombophilia and retinal vein occlusion

PURPOSE

To perform a pilot study on the prevalence of familial thrombophilia in all cases of retinal vein occlusion with no known risk factors.

METHODS

Over the 1 year study period 71 patients presented with a new diagnosis of retinal vein occlusion (age 28-90 years). Fifty-five (77%) were excluded because of local predisposing factors. The remaining 16 (23%) had a full risk factor history taken and blood investigations of rheological factors and thrombophilia including tests for the factor V Leiden mutation, prothrombin G20210A allele and hyper-homocystinemia.

RESULTS

Of those with no local predisposing factors, 3 patients had antiphospholipid antibodies, 3 had raised fibrinogen levels, 4 had hyper-homocystinemia and 1 was heterozygous for the Leiden mutation. Other lifestyle risk factors such as obesity, smoking and a positive family history of venous thrombosis were not uncommon. No patient had the prothrombin G20210A variant.

CONCLUSIONS

It seems likely that several risk factors, both genetic and acquired, need to be present for thrombosis to occur. In investigating a new patient with a retinal vein occlusion one should test for hypertension, glaucoma and diabetes mellitus. Estimation of plasma viscosity and a full blood count are cheap investigations which may reveal neoplasia or vasculitis, and lipid levels should be estimated. In a young patient or one with an unexpected vein occlusion and a personal or family history of thrombosis, a hypercoagulable state may rarely be identified. This additional testing should include testing for antiphospholipid antibodies and a full thrombophilia screen including the factor V Leiden mutation, homocysteine and the prothrombin variant as part of a clinical trial. Until the role of these markers in thrombosis is better defined in relation to causation of retinal vein occlusion and treatment has been shown to improve outcome, we can not recommend them for routine testing. If a hereditary defect is found, referral should be made to a hematologist and consideration given to anticoagulation and screening of family members to prevent further thrombotic episodes. Retinal vein occlusions are multifactorial in origin except in rare cases.

Central retinal vein occlusion: review of management

Central retinal vein occlusion is usually a disease of the elderly and is often associated with systemic vascular disease, e.g., hypertension, diabetes mellitus, arteriosclerotic vascular disease. Younger patients, especially those less than 45 years of age, with retinal vein occlusion should be evaluated carefully for the possibility of an underlying thrombotic tendency. The authors describe the ocular manifestations, pathogenesis, associated conditions, patient evaluation, and treatment of patients with central retinal vein occlusion.