Differential diagnosis of leukocoria and strabismus Figure 3 (a) Coats’ disease: right leukocoria in a 2 year-old boy. (b) Coats’ disease: yellowish exudates covering the whole macular area. (c) Coats’ disease: extensive peripheral telangiectatic vessels and partial retinal detachment. (d) Coats’ disease: total bullous retinal detachment posterior to the clear lens and vascular telangiectasias. In the hereditary form of retinoblastoma there is also a risk of trilateral involvement, this the association of retinoblastoma, usually bilateral (90%) but not exclusively, with an intracranial neuroblastic tumor, commonly in the region of the pineal gland (pinealoblastoma), these cells being linked to the RB1 gene and of the same phylogenic origin as retinal tissues (De Potter et al 1994; Kivelä 1999). The vital prognosis for these cerebral tumors is very poor. Furthermore, children carrying the RB1 gene suffer life-long exposure to other non-ocular primary malignancies, in particular osteosarcoma of the orbit or elsewhere (Moll et al 1997, 2001; Abramson 1999; Abramson et al 2001). The risk is 1% per year of evolution and is particularly high in children having received radiotherapy before the age of one year (Abramson 1999). Coats’ disease (primary retinal telangiectasia) Coats’ disease, or primary (congenital) retinal telangiectasia, is a rare exudative retinopathy (Coats 1908; Balmer 2005; Shields et al 2001) (Figure 3). Unilateral in 90% of cases, the Clinical Ophthalmology 2007:1(4) disease habitually affects young males (80%) between 5 and 10 years old, although it can appear much earlier, before one year of age. It is non hereditary, probably congenital, with no known associated systemic diseases. Clinical characteristics include three major features: retinal telangiectasia in the form of strings of fusiform dilatations of the retinal vessels, usually peripheral; massive yellowish exu- dates within and underlying an edematous retina, sometimes giving a pseudo-tumoral appearance with a predilection for the macular area; exudative, sometimes total, retinal detachment (Figures 4b, 4c, and 4d). The exudates may be responsible for a luminous leukocoria (Figure 3a) but, in the presence of retinal detachment, this will take on a greyer hue. The evolution of Coats’ disease is variable. It may stabilize, although often with loss of central vision due to macular lipid deposits, or deteriorate with total exudative retinal detachment (Figure 3d), iridis rubeosis, neovascular glaucoma, cataract, uveitis, phthisis bulbi and, ultimately, total and deﬁnitive loss of vision. 435