Description

Osteogenesis imperfecta is a group of inherited disorders, usually inherited as an autosomal dominant trait, characterised by quantitative and qualitative defects in type I collagen.1 2 Osteogenesis imperfecta is characterised by increased bone matrix mineralisation resulting in increased bone stiffness and brittleness, making them prone to fracture (figure 1A,B). Similarly, excessive mineralisation of the elastin-rich Bruch’s membrane can lead to ruptures in the membrane with or without concurrent disruption of the overlying layers of the retina and the underlying choriocapillaris.3 Mineralisation of Bruch’s membrane in this way is responsible for the formation of angioid streaks (figure 1C,D). This localised defect can lead to the formation of choroidal neovascularisation—as seen in the left eye (figure 1D), which can result in the formation of a disciform scar with a detrimental effect on visual acuity—as observed in the right eye.

• Download figure
• Open in new tab
• Download powerpoint

Figure 1

(A–B) A clinical photograph of a short-statured male with bowing of the legs and bruising of the knee joint, features characteristic of osteogenesis imperfecta. (C–H) Depicts bilateral, radially arranged, angioid streaks, a spray of comets and comet-tails giving the appearance of ‘comet-rain’ (white arrow (C, D), with a choroidal neovascular scar in the right eye (C), and active choroidal neovascularisation in the left eye with an active bleed (yellow arrow, D). Optical coherence tomography through the macula depicts the breach in Bruch’s membrane—Retinal pigment epithelium (RPE) in both eyes (E, F). Resolution of the foveal bleed in the left eye following antivascular endothelial growth factor injection (G, H).

Comet lesions are solitary, nodular, crystalline or white spots of chorioretinal atrophy, with a tapered tail of retinal pigment epithelium atrophy, oriented towards the optic disc, irrespective of their location.4 These lesions are more commonly appreciated in pseudoxanthoma elasticum-related retinopathy. A spray of comet lesions creates an appearance of ‘comet rain’, typically arranged between the main vascular arcades. We could appreciate the comet rain appearance inferiorly between the inferotemporal and inferonasal arcades in our patient (figure 1C,D). These lesions are thought to form due to focal interruption of Bruch’s membrane with consequent degeneration or absence of the underlying retinal pigment epithelium, triggering an attempt to repair the overlying photoreceptors.5

Visual loss from the complications of choroidal neovascular membrane formation, depicted by the breach in the Bruch’s membrane—RPE in both eyes on Optical Coherence Tomography (OCT) (figure 1E,F) can be delayed by antivascular endothelial growth factor therapy. Therefore, it is imperative that patients with osteogenesis imperfecta have regular retinal evaluation, so as to enable timely diagnosis and treatment (figure 1G,H). The presence of a macular scar at the time of initial presentation in this patient can be attributed to the failure of retinal screening.