# A Case of Knobloch Syndrome With Lens Dislocation Resembling Homocystinuria

## TL;DR

A 39-year-old woman with lifelong visual issues was diagnosed with Knobloch syndrome, a rare genetic disorder, after presenting symptoms similar to homocystinuria.

## Contribution

This case highlights an adult presentation of Knobloch syndrome with retinal changes and lens dislocation mimicking homocystinuria.

## Key findings

- A homozygous frameshift mutation in COL18A1 confirmed Knobloch syndrome type 1.
- Lens dislocation and retinal degeneration mimicked homocystinuria but were linked to a genetic cause.
- Early genetic diagnosis is crucial for management and family counseling in such cases.

## Abstract

We report a 39‐year‐old woman with lifelong visual impairment who presented in June 2024 with progressive visual deterioration in her right eye. Ophthalmologic evaluation revealed severe high myopia, vitreoretinal degeneration, phthisis bulbi of the left eye, and downward lens dislocation of the right eye. Neurological workup revealed bilaterally blurred optic discs, an elevated cerebrospinal fluid opening pressure of 31 cm H2O that normalized on repeat lumbar puncture, nonspecific white matter signal changes on MRI, and bilateral frontal polymicrogyria. Initial mild homocysteine elevation prompted consideration of homocystinuria; however, whole‐exome sequencing identified a homozygous frameshift mutation in COL18A1 (c.2824_2831del, p.Gly942Argfs*142), confirming Knobloch syndrome type 1. This case illustrates an adult presentation of Knobloch syndrome with retinitis pigmentosa‐like retinal changes and lens dislocation mimicking homocystinuria.

Knobloch syndrome (KNO) should be considered in adults with congenital visual impairment, lens dislocation, and retinal degeneration, especially with a positive family history and consanguinity. Differentiation from homocystinuria and Marfan syndrome relies on detailed ocular examination and genetic testing. Early genetic diagnosis guides management and family counseling.