# Differences in Visual Acuity Among Hermansky-Pudlak Syndrome Subtypes

## TL;DR

This study found that patients with HPS-3 have better visual acuity than those with HPS-1, despite similar eye structures.

## Contribution

The study identifies a significant difference in visual acuity between HPS subtypes in Puerto Rican patients.

## Key findings

- HPS-3 patients had significantly better visual acuity than HPS-1 patients.
- No significant differences were found in refractive error, macular volume, or macular thickness between subtypes.

## Abstract

Background

Patients with Hermansky-Pudlak syndrome (HPS) typically present with a triad comprising tyrosinase-positive oculocutaneous albinism, a tendency to bleed easily, and ceroid accumulation in multiple tissues. Ocular findings in patients with HPS include poor vision, refractive errors, photophobia, periodic alternating nystagmus, iris transillumination, foveal hypoplasia, and albinotic mid-peripheral retina. Among these, foveal hypoplasia and reduced foveal thickness are key structural abnormalities contributing to impaired visual acuity. While HPS is rare worldwide, its prevalence in Puerto Rico is notably high due to founder mutations in HPS1 and HPS3, which account for most cases on the island.

Methodology

A retrospective chart review of 106 Puerto Rican patients with HPS was performed to evaluate differences in ophthalmic findings among patients with HPS subtypes. A comprehensive ophthalmic evaluation, including macular optical coherence tomography, was conducted to assess macular structure and foveal thickness. Genetic testing identified HPS1 (16-bp duplication) and HPS3 (3,904-bp deletion) mutations, leading to HPS-1 and HPS-3, respectively, the most prevalent in Puerto Rico. Descriptive and statistical analyses were used to evaluate genotype-phenotype correlations. The main outcome measures, including visual acuity, refractive error, macular volume, and macular thickness, were measured and compared between HPS-1 and HPS-3 patients.

Results

Among 107 patients, 72.9% had HPS-1, and 26.2% had HPS-3. HPS-3 patients had significantly better visual acuity than HPS-1 (p < 0.005). There were no significant differences between subtypes in refractive error, macular volume, or macular thickness.

Conclusions

HPS remains underdiagnosed, particularly outside Puerto Rico. HPS-1 is the most prevalent subtype, followed by HPS-3. This study identified a significant difference in visual acuity between subtypes. Early ophthalmic evaluation and genetic screening are essential for timely diagnosis and management.