Song and co-workers report a striking clinical picture, which they named “multifocal vitelliform paravascular retinopathy” (MVPR), and state that this is a unique and novel disorder within the vitelliform spectrum. The authors note that toxicity of mitogen-activated protein kinase kinase (MEK) inhibitor medication was excluded as a cause of serous/vitelliform lesions. Of note, the use of hair dye containing MEK-inhibitor–like aromatic amines can cause a similar picture, and this could be considered as a potential disease cause. , However, the lesions in the aforementioned conditions are generally more variable in their appearance on follow-up, whereas the patients reported by Song et al had a comparatively stable aspect of the lesions. Also, in contrast to some of the patients described in the paper, the electro-oculogram (EOG), as a reflection of the function of the entire retinal pigment epithelium, is often abnormal in MEK-inhibitor–associated retinopathy, supposedly due to toxicity of the MEK inhibitor to the retinal pigment epithelium.
The authors may have introduced selection bias because they included only patients with paravascular small vitelliform lesions who did not have vitelliform lesions in the central macular area. In the cases of which images were provided, there still seems to be variability in the number of lesions, and some patients also had vitelliform lesions in the peripheral macula outside the vascular arcades. In a previous study, we described 15 patients with multifocal vitelliform dystrophy who all had bilateral vitelliform satellite lesions in addition to a central vitelliform lesion. Nine of these 15 patient carried disease-causing variants in the BEST1 gene; 7 of 9 had an autosomal-dominant inheritance pattern for macular disease, and all 9 patients had an abnormally low or absent EOG light rise. These patients can thus be considered to have a multifocal variant of autosomal dominant Best vitelliform dystrophy. ,
Interestingly, the remaining 6 patients in our study did not have a disease-causing variant in the BEST1 gene; 2 of 6 patients had an abnormally low (but not absent) light rise on EOG, and these 6 non– BEST1 -associated patients had a higher number satellite vitelliform lesions compared to the BEST1 -associated cases, often along the vascular arcades and above the optic disc. This subgroup may actually be quite similar to the MVPR phenotype described by Song et al, apart from the fact that the patients in their paper did not have a central vitelliform lesion; but this was part of the authors’ selection criteria. In addition, analysis of potentially associated genetic risk factors such as BEST1, PRPH2 , and IMPG1/2 was performed in only a minority of their cases, as was EOG. It is therefore not clear whether the patients constitute a clinically (and genetically) homogeneous group, apart from the localization of their vitelliform lesions. To enable a better assessent of the homogeneity and phenotypic spectrum of the clinical picture that the authors describe as MVPR, larger patient cohorts, also including patients who have central vitelliform lesions, with comprehensive genetic testing, and electrophysiological testing including EOG, can provide further insight.
CRediT authorship contribution statement
CAMIEL J.F. BOON: Conceptualization, Investigation, Writing – original draft, Writing – review & editing.
FUNDING: None.
FINANCIAL DISCLOSURE: None reported.
CONFLICT OF INTEREST: None.
REFERENCES
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