Birdshot Retinochoroidopathy



Fig. 20.1
Characteristic multiple deep cream-colored lesions in a patient with BSRC



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Fig. 20.2
Fluorescein angiography demonstrating retinal vasculitis in a patient with BSRC


A newer criterion for research purposes has been published and includes supportive findings such as the presence of HLA-A29 positivity [19]. It also considers keratic precipitates, posterior synechiae, or the presence of other causes of multifocal choroiditis as exclusion criteria [20].

HLA-A29 positivity is not required for the diagnosis of BSRC, but given the high correlation, one should consider revisiting the diagnosis if the test is negative [21].

Imaging modalities and ancillary tests are helpful in the diagnosis of BSRC. Fluorescein angiography (FA) is used to evaluate retinal vascular leakage and associated CME and disc leakage. Indocyanine green angiography (ICG) demonstrates the presence of multiple hypocyanescent lesions (Fig. 20.3) that are smaller and do not correspond with the lesions seen clinically. Ocular coherence tomography (OCT) testing is useful in the evaluation of CME and also to assess changes in the outer retinal layers consistent with damage to the photoreceptors due to long-standing disease. Electroretinography (ERG) [6] and Goldmann visual field testing [22] demonstrate abnormalities in long-standing disease due to global retinal dysfunction.

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Fig. 20.3
ICG angiography in a BSRC patient demonstrating hypocyanescent lesions



Differential Diagnosis


The clinical features of BSRC are very distinct as the disease involves both the retina and choroid. These findings can be subtle early in the disease and the diagnosis more difficult to establish. Conditions that can be considered in the differential diagnosis of BSRC are sarcoidosis [23], syphilis, tuberculosis, intraocular lymphoma [24], multifocal choroiditis, and other “white dot syndromes” [25]. Demographics, systemic symptoms, ancillary testing, blood work, and sometimes surgery (i.e., diagnostic vitrectomy), are useful in differentiating these conditions from BSRC.


Treatment


Multiple different treatment approaches have been utilized in the management of BSRC but there is no consensus regarding the ideal treatment. Many patients can develop a chronic course leading to vision loss if effective treatment is not started. A small fraction of patients may develop a self-limiting disease but this is uncommon.

Historically, treatment was reserved for patients that developed macular edema but this approach does not take into account loss of vision due to global retinal dysfunction [5].

BSRC responds well to systemic or periocular/intravitreal steroids but in most cases, the disease progresses after steroid taper or discontinuation. Steroids are used acutely and during exacerbations but are usually not enough to maintain control of the disease. It has been reported that more than 50 % of patients treated with steroid monotherapy may experience deterioration in visual acuity over time [26].

A uveitis expert panel published guidelines for the use and monitoring of immunosuppressive drugs in ocular inflammatory diseases in 2000. They suggested that patients with BSRC and other posterior uveitides may benefit from the use of immunosuppressive drugs as they appear to have a poor long-term outcome from steroid therapy alone [27].

Different immunomodulatory therapy (IMT) agents have been reported to control the progression of this disease including antimetabolites, cyclosporine [26], TNF alpha blockers [28], intravenous immunoglobulin [29], etc.

Ideally, the management of a patient with noninfectious uveitis should be based on a step-up or stepladder approach, consisting of intensification of treatment guided by disease severity [30]. One strategy when dealing with BSRC is to start systemic or periocular/intravitreal steroids acutely and discuss the likely need for further therapy. If IMT is initiated, antimetabolites such as mycophenolate or methotrexate are good first line agents [31]. If the disease continues to be active and/or steroids are unable to be tapered, cyclosporine can be added as adjuvant therapy [32]. In patients with persistent inflammation despite the use of these drugs, the transition to a TNF alpha inhibitor [28] or the use of an intravitreal steroid implant such as the fluocinolone acetonide intravitreal implant should be considered [33].


Monitoring of Disease Activity


Multiple imaging modalities and ancillary tests are utilized to follow course and response to treatment of patients with BSRC. FA is used to follow resolution of vascular and disc leakage and CME. ICG can demonstrate involution of choroidal lesions. OCT is useful to evaluate macular changes such as CME or the developing of subretinal fluid associated with choroidal neovascularization. Progressive global retinal dysfunction can be measured by electroretinography (ERG) [6] or by Goldmann visual field testing [22]. Goldmann testing is preferred over Humphreys automated perimetry as it test a broader field and is likely more sensitive to earlier peripheral retinal changes [22].

Annual ERGs can help monitor stability or progression in patient with BSRC [6]. ERG in association with other ancillary testings is a useful tool to establish efficacy of treatment [6].


Prognosis


This disease is often characterized by multiple relapses or chronically active, smoldering inflammation resulting in loss of useful vision in one or both eyes in 40 % of patients [2]. BSRC is a slowly progressive disease with profound dysfunction of vision that may not be reflected in Snellen visual acuity [4]. Loss of visual field defects is due to global retinal dysfunction and loss of central vision is due to CME, or less common CNV.


Conclusion


BSRC is an uncommon, chronic ocular inflammatory condition involving the posterior segment of the eye linked to the presence of the HLA-A29 antigen which is found in 95 % of patients with the disease. Regional and systemic corticosteroids are an effective initial treatment modality, but most patients will require therapy with systemic immunomodulatory therapy to control the disease and prevent loss of vision.


References



1.

Franceschetti A, Babel J. La choriorétinite en taches de bougie, manifestation de la maladie de Besnier-Boeck. Ophthalmologica. 1949;118:701–10.CrossRefPubMed

Aug 17, 2017 | Posted by in OPHTHALMOLOGY | Comments Off on Birdshot Retinochoroidopathy

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