Year : 2000 | Volume
: 48 | Issue : 2 | Page : 135--7
Osseous choristoma of the choroid
L Verma, P Venkatesh, NC Lakshmaiah, SP Garg, HK Tewari
Rajendra Prasad Centre for Ophthalmic Sciences, All Institute of Medical Sciences, New Delhi, India
Rajendra Prasad Centre for Ophthalmic Sciences, All Institute of Medical Sciences, New Delhi
|How to cite this article:|
Verma L, Venkatesh P, Lakshmaiah N C, Garg S P, Tewari H K. Osseous choristoma of the choroid.Indian J Ophthalmol 2000;48:135-7
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Verma L, Venkatesh P, Lakshmaiah N C, Garg S P, Tewari H K. Osseous choristoma of the choroid. Indian J Ophthalmol [serial online] 2000 [cited 2021 Sep 18 ];48:135-7
Available from: https://www.ijo.in/text.asp?2000/48/2/135/14889
Osseous choristoma of the choroid, also called choroidal osteoma, is a very rare and unusual form of intraocular ossification. We report a case of choroidal osteoma in a young healthy male that to the best of our knowledge is the first report from India.
Indian J Ophthalmol 2000;48:135-37
So far, only about 20 cases of choroidal osteoma (osseous choristoma) have been reported in the literature. Although this benign tumour has characteristic clinical, fluorescein angiographic and imaging features, it is known to simulate several other conditions such as amelanotic choroidal melanoma and nevus, metastatic choroidal carcinoma, choroidal haemangioma, metastatic and dystrophic intraocular calcification.
A 37-year-old male patient was referred to the Uvea Services with a diagnosis of choroidal granuloma in his left eye. The history revealed that the patient had incidentally noticed a decreased vision in his left eye for about two months. He had no other ocular or systemic complaints and no history of ocular trauma or symptoms suggestive of any past intraocular inflammation.
On ocular examination, the best corrected visual acuity was 6/6 and 6/18 in the right and left eye respectively. In both eyes projection of rays was accurate and ocular adnexa and anterior segment examination did not show any abnormalities. Applanation intraocular pressure was 16mmHg in both eyes.
Fundus examination of the left eye showed a clear media and a normal optic nerve head. There was a subretinal, ovoid, slightly elevated yellowish mass measuring about two disc diameters in size (3mm x 2.5mm) and situated 1 disc diameter away from the temporal edge of the optic nerve head. The margins of the mass were well defined and its lower margin extended into the foveal zone superiorly. A crescentric subretinal haemorrhage along the lower margin of the mass and a shallow sensory detachment of the macula were also present [Figure:1]. The overlying retinal vessels seemed partially obscured. Contact fundus biomicroscopy did not show any cells in the posterior vitreous.
We considered the possibility of a non-inflammatory mass lesion because of an absence of retinal oedema and vitreous reaction. A presumptive diagnosis of osteoma of the choroid with a choroidal neovascular membrane was made. A-Scan ultrasonography showed a high reflectivity spike persisting up to 40dB. Behind this there was a rapid attenuation of echoes. B-Scan ultrasonography showed a focal, slightly elevated, highly echo-reflective lesion merging with the retino-choroidal complex. The mass persisted at lower scanning sensitivity. B-scan ultrasonography also showed a distinct acoustic shadowing of the retro-ocular structures posterior to the mass giving the classical appearance of a pseudo-optic nerve [Figure:2a] and [Figure:2b].
Fluorescein angiography demonstrated a patchy hyperfluorescent lesion in the early phases with diffuse intense hyperfluorescence in the late phases. A lacy pattern of hyperfluorescence indicative of subretinal neovascular membrane was evident in the early phases on fluorescein angiography [Figure:3]. Indocyanine green imaging (ICG) revealed a diffuse hypofluorescence in the early frames with the normal choroidal vessels stopping abruptly at the margin of the mass. A few subtle, barely visible intrinsic vessels were seen next followed in the late frames by a diffuse leakage into the mass [Figure:4].
Computed tomography (CT) showed a characteristic, well defined homogeneously radio-opaque plaque of bone density corresponding to the lesion in the left eye [Figure:5]. On Magnetic resonance imaging (MRI), the mass appeared only as a hypointense T2W image.
The choroidal neovascular membrane was treated using diode red laser. At two months follow up the lesion did not show an increase in size. Fluorescein angiography performed at this time did not show any change compared to the pre-laser fluorescein angiogram [Figure:6]. A post-laser ICG study could not be done as the patient left for another country for further consultation.
Intraocular calcification and ossification has been known to develop in several clinical conditions. However choroidal osteoma was recognized as a distinct entity only in 1978 when it was first described by Gass and coworkers. it is a choroidal tumour composed of mature bone in various stages of calcification. Histopathologically the choroid is replaced by a plaque-like bony lesion. The bone is mature, and cancellous in nature with a hypocellular marrow lacking haemopoeitic tissue.
Choroidal osteoma has been reported to occur typically in healthy young females in their second to third decade. However, it is also reported in males, in children and in older adults. So far there have been only three such reports from people of oriental descent, all from Japan.
Clinically, choroidal osteoma is unilateral in 75% of patients and tends to be located in the peripapillary or juxtapapillary area and may extend into the macular region. The size of the lesion may range from 2 - 22mm and the elevation, 0.5 - 2.5mm. Early in its evolution it may appear orange in colour, to a choroidal haemangioma. It later turns yellow due to degeneration of the overlying retinal pigment epithelium. The sharp border helps distinguish an osteoma from a haemangioma. Complications that have been reported in association with choroidal osteoma include sensory detachment and choroidal neovascular membrane.[5-7] It has been reported that about a third of patients with choroidal osteoma develop choroidal neovascular membrane. Because of thinning and degeneration of the overlying retinal pigment epithelium, treating such choroidal neovascular membranes might require multiple sessions.
In our patient a diagnosis of choroidal osteoma was made based on the characteristic clinical and ultrasonographic features. Findings on fluorescein angiography, ICG imaging, computed tomography and MRI were also consistent with the descriptions of choroidal osteoma in the literature.[5-
Accurate diagnosis of this rare tumour is important for two reasons. Firstly, it is benign unlike other lesions such as amelanotic choroidal melanoma, choroidal granuloma and metastatic choroidal carcinoma which it may simulate; hence it does not require any treatment. Secondly, these patients have to be kept under periodic observation as treatable choroidal neovascular membranes are known to develop.
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