Low-grade “benign” birdshot retinochoroiditis: prevalence and characteristics

The appraisal of BRC, after its first reports [1, 2] in the early nineteen–eighties, has evolved over the years. The first two reports indicated that systemic corticosteroid therapy was not very efficient [1, 2] and BRC became to be perceived as a relatively benign disease probably not needing aggressive treatment [5, 19, 30, 31]. This opinion also prevailed because visual acuity remained conserved for long periods. This is explained by the fact that, although profuse macular and retinal edema was present, peculiarly the fovea was relatively spared in a large proportion of cases [3]. When longer follow-up data became available, it was shown that morbidity and complications were in fact of substantial importance, including severe visual field impairment, retinal thinning and atrophy with pseudo-retinitis pigmentosa evolution in some cases [32], epiretinal membranes as well as choroidal atrophy [16]. Numerous reports began to demonstrate that steroidal and non-steroidal immunosuppression was needed to improve the outcome of BRC in the long run and this became the standard of care [21, 22, 33]. It was further shown that, when considering visual field as the functional parameter to decide upon treatment for BRC cases, treatment was started earlier [23]. The grade of early activity could also be determined clearly thanks to ICGA showing choroidal foci and choroidal vasculitis, two signs of activity [34‐38]. On the other hand, it became clear that oval depigmented birdshot fundus lesions, representing stromal scars, were not influenced by therapy and were not a sign of disease activity [12]. ICGA signs and the presence of visual field disturbances allowed both an early diagnosis and an early treatment, before oval depigmented BRC fundus lesions were noted [23]. It was even shown that, when treated early and before appearance of oval depigmented BRC lesions, those lesions never developed [23]. The belief, in the nineteen–eighties, that BRC was a benign disease was possibly also based on the fact that early reports certainly included benign cases. Such mild cases certainly exist and are important to identify such cases in order not to overtreat patients who do not need it. Data on such patients are reported in our study. At presentation, in case of unilateral functional involvement, an attempt was made to treat locally, delaying systemic treatment until disease progression was documented. In half of the patients, an attempt was made to start treatment with sub-Tenon’s injections of triamcinolone acetonide (40 mg). In 5/8 patients, periocular treatment did not halt progression and systemic treatment had to be introduced. In the 3/20 patients (15%) reported here, progression was halted by periocular therapy and they could be termed mild cases, whereas 85% of patients needed systemic treatment. In our three mild patients, as expected, BRC fundus lesions did not progress nor regress as they are choroidal scars and not active lesions. FA signs were minimal and remained stable. In contrast, ICGA lesions, a witness of disease activity, did regress indicating that there was no active disease progression until the last follow-up. In this group, the disease resulted from a minimally aggressive process. OCT and EDI-OCT showed that both retinal and choroidal structures were preserved without significant thinning after a mean follow-up of more than 9 years.

Our survey shows indeed that there is a small proportion (15%) of low-grade BRC cases that never go over to a stage where systemic therapy is needed. In contrast, when systemic therapy is needed, an aggressive and quasi-lifelong therapy has to be applied, mostly consisting of a combination of two immunosuppressive agents [3, 12, 21, 22, 32]. Therefore, it is important to identify those cases without massive involvement at presentation to try to sort out the patients who do not need systemic therapy, as we know that, in that case, treatment is going to be heavy and prolonged.