**Core Concept**
Interstitial keratitis is a corneal inflammation characterized by a diffuse, non-purulent, and non-suppurative infiltration of the corneal stroma, often associated with congenital syphilis. This condition is part of Hutchinson's triad, a classic clinical manifestation of congenital syphilis.

**Why the Correct Answer is Right**
Hutchinson's triad consists of interstitial keratitis, sensorineural hearing loss, and Hutchinson's teeth (notched incisors). Interstitial keratitis occurs due to the immune-mediated response to the treponemal infection, leading to inflammation of the corneal stroma. This condition is often bilateral and can result in corneal scarring, vision impairment, and potentially blindness if left untreated. The pathogenesis involves the activation of the immune system, which releases various cytokines and chemokines, resulting in the recruitment of inflammatory cells to the cornea.

**Why Each Wrong Option is Incorrect**
**Option A:** Disciform keratitis is a type of corneal inflammation characterized by a localized, non-purulent, and non-suppurative infiltration of the corneal stroma, often associated with herpes simplex keratitis. It is not typically associated with congenital syphilis.
**Option C:** Phlyctenular keratitis is an immune-mediated condition characterized by the formation of small, nodular lesions on the cornea, often associated with staphylococcal blepharitis or atopic dermatitis. It is not a characteristic feature of congenital syphilis.
**Option D:** Mooren ulcer is a type of non-infectious, autoimmune corneal ulceration characterized by a rapidly progressive, non-healing ulcer on the cornea. It is not typically associated with congenital syphilis.

**Clinical Pearl / High-Yield Fact**
It is essential to recognize the classic clinical manifestations of congenital syphilis, including Hutchinson's triad, to diagnose and manage this condition promptly. Early diagnosis and treatment can prevent long-term complications, such as interstitial keratitis, sensorineural hearing loss, and Hutchinson's teeth.

**✓ Correct Answer: B. Interstitial keratitis**