Retinal pigment epithelium (RPE) humps have recently been described as inward elevations of the RPE over large choroidal vessels in eyes with pathologic myopia (PM).1,2 These humps can be found in about 50% of highly myopic eyes in at least one macular optical coherence tomography (OCT) scan. RPE humps are benign findings, typically not related to any retinal damage or pathologic sub-RPE material; the majority of cases are asymptomatic and do not require any treatment.3 In the first descriptive report, RPE humps were not directly associated with any sign of retinal pathology. With the prospective collection of these cases, an association between RPE humps and several sight-threatening retinal complications has been found. These cases have been named “complicated RPE humps.”
Here we report a series of complicated RPE humps, imaged by multimodal imaging. These associations are novel, and we deem they might represent relevant diagnostic findings in dealing with patients featuring PM.
Classic RPE humps have been described as oval-flat or pyramidal-shaped RPE elevations, corresponding to large choroidal vessels. Due to the lack of choroidal stromal tissue in highly elongated myopic eyes, these vessels lift the RPE, determining a hump-like profile on structural OCT scans.2 The choriocapillaris and other large choroidal vessels are usually absent around the RPE humps; however, the RPE is regular and continuous over these lesions, and areas of myopia-induced RPE atrophy or degeneration are generally distant from the hump location. The OCT bands corresponding to the inner retinal layers, albeit distorted, appear normally represented in simple, benign RPE humps. Differently from pigment epithelium detachments, classic RPE humps do not present any pathological material or deposit between the RPE and the BM, whereas contrary to myopic CNV, these lesions do not feature any sign of pathologic blood flow on OCT angiography or dye hyperpermeability on fluorescein angiography (FA).
On the contrary, in this series, we presented a set of complications occurring over RPE humps associated with high myopia. These complications included active multifocal choroiditis inflammatory lesions, BM rupture with subretinal simple bleeding, and myopic CNV, which are all part of the clinical spectrum of high myopia and can be associated with a tomographic profile very similar to the one seen in RPE humps.1–4 Because RPE humps usually do not require any treatment, it is important to distinguish the features of uncomplicated RPE humps from those of complicated lesions, which underlie other potential sight-threatening pathological conditions, claiming timely therapeutic interventions.2 In this setting, multimodal imaging, including OCT, FA, and OCT angiography, plays a relevant role.5–7
Hemorrhagic BM ruptures are often associated with the onset of new lacquer cracks, which are prone to form over perforating scleral vessels.8,9 Large choroidal remnants, indenting the overlying RPE, may contribute to raising the risk of cracks in the stretched Bruch's membrane.
Although the prevalence of myopic CNV in eyes with RPE humps was not significantly different from eyes without humps in the original study, the development of myopic CNV over a hump was still not observed.2 As myopic CNVs are sometimes associated with perforating scleral vessels, we can speculate that these perforating scleral vessels deform the BM, giving an RPE hump appearance as observed in our case.10,11
PM is a predisposing factor of several inflammatory eye diseases that involve the posterior segment of the eye known as inflammatory choriocapillaropathies and including multifocal choroiditis and punctate inner choroidopathy.12 The most useful complementary investigation is indocyanine green angiography, which shows hypofluorescent dots indicating chorioretinal scars or capillary nonperfusion, that correspond to late hyperfluorescent nondiffusing spots on FA. Multifocal choroiditis inflammatory lesions have some peculiar features also on OCT, including sub-RPE material and choroidal hyperreflectivity.12 The development of active inflammatory lesions over RPE humps may hinder the recognition of these precious features. On careful examination of the RPE humps characteristic of our case, we observed the presence of quite peculiar “volcano-like” apertures of the RPE associated with vertical hyperreflective material, which can serve as a useful OCT clue to differentiate uncomplicated RPE humps from active inflammatory lesions in the setting of multifocal choroiditis. Additional imaging modalities, including OCT angiography, allowed to exclude the presence of an underlying secondary CNV.
In these small series, we also observed that complications over RPE humps responded well to traditional therapies used in each scenario. Additional and more powerful studies are needed to assess if these complications may have a different prognosis when occurring over RPE humps.
In conclusion, different complications can occur over myopic RPE humps. Regular follow-up with appropriate examinations can help to recognize these events and offer the most proper treatment timely.