A 40-year-old man presents to Ophthalmology clinic with concern for visually significant glare while driving at night. He has also noticed a change in the color of his right eye over the last year. He denies symptoms of eye pain, redness, or discharge. The unaffected iris appears brown with no color irregularity. Significant features of the appearance and slit lamp exam of the right eye are shown in the images below. These findings are absent in the left eye. What is the most likely diagnosis?
A. Posner-Schlossman Syndrome
B. Congenital heterochromia
C. Fuch’s Heterochromic Iridocyclitis
D. Waardenburg’s Syndrome
Correct answer: C. Fuch’s Heterochromic Iridocyclitis
Heterochromia, diffuse endothelial keratic precipitates, and unilateral cataract are all supportive of a diagnosis of Fuch’s Heterochromic Iridocyclitis (FHI). FHI is characterized by chronic low-grade, unilateral inflammation of the iris and generally has a good prognosis. The etiology is unknown but there are associations with HSV, CMV, Rubella virus, and toxoplasmosis infections. Histopathology would demonstrate atrophied iris stroma, melanocytes with depigmentation, and ciliary body fibrosis and atrophy. Patients are typically asymptomatic until noticing iris discoloration or visual symptoms from cataract in the affected eye. Any unilateral cataract in a young patient with absence trauma or steroids should prompt the clinician to strongly consider FHI as the etiology. Iris rubeosis may be seen in FHI as well, where gonioscopy demonstrates tiny bridging vessels traversing the trabecular meshwork. Patients with FHI and iris rubeosis may develop hyphema when the anterior chamber is accessed through paracentesis or surgery, and this is known as Amsler’s sign. Management is generally conservative as the inflammation is low grade and minimally responsive to steroids. If there is a flare, short durations of topical steroids are indicated. Secondary glaucoma may develop in some patients with FHI but is usually responsive to medical management. Most clinical courses involve regular interval follow-up with monitoring for cataract and/or glaucoma.
Posner-Schlossman syndrome (A) is a diagnostic consideration, given that patients with this condition can also present with heterochromia and keratic precipitates. A short course of topical steroids can be useful for distinguishing FHI from PSS. However, heterochromia is a rarer finding in PSS and keratic precipitates are usually inferiorly distributed on the endothelium. Additionally, episodic unilateral blurred vision accompanied by ocular pain would be more consistent with a diagnosis of PSS. Congenital heterochromia (B) and Waardenburg syndrome (D) are congenital disorders, and the ocular findings of heterochromia would have presented at birth.
Sources: Eyewiki, “Fuchs Heterochromic Iridocyclitis and Secondary Glaucoma”; EyeRounds, “Fuchs Heterochromic Iridocyclitis”
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