# Genotype-phenotype correlations in PSACH/EDM1 patients with COMP gene variants: a comprehensive review of 830 cases

## TL;DR

This study reviews 830 cases of PSACH and EDM1 to understand how COMP gene variants correlate with disease severity and symptoms.

## Contribution

The study provides a comprehensive analysis of genotype-phenotype correlations in PSACH/EDM1, identifying specific COMP gene variant hotspots and their clinical associations.

## Key findings

- PSACH shows earlier onset, shorter stature, and more severe skeletal features compared to EDM1.
- Missense variants in T3–4 and T3–5 are more common in EDM1, while in-frame variants like p.Asp473del are specific to PSACH.
- Exon 13 and the T3 repeat domain are the most frequently affected regions in COMP gene variants.

## Abstract

Pseudoachondroplasia (PSACH) and multiple epiphyseal dysplasia-1 (EDM1) are two rare skeletal diseases that represent distinct endpoints of a continuous phenotypic spectrum with substantial clinical overlap, caused by variants in the gene coding cartilage oligomeric matrix protein (COMP).

To summarize the clinical characteristics of PSACH/EDM1 and variants of COMP gene, as well as to explore the correlations between them.

PubMed, China National Knowledge Infrastructure, and Wanfang were searched for case reports and case series of patients with genetic diagnosis of PSACH/EDM1 from the inception to 24 March 2025. The clinical characteristics and gene variants of enrolled patients were analyzed and compared to explore genotype-phenotype correlation.

A total of 830 PSACH/EDM1 patients (471probands) harboring 224 different variants of COMP gene were enrolled from 106 articles, with missense variants accounting for the majority (80.8%). Exon 13 (183 probands, 38.9%) and type III (T3) repeat domain (413 probands, 87.7%) were the most commonly affected regions, with c.1417_1419del (p.Asp473del) being the most common hotspot variant. Compared with EDM1, PSACH manifested earlier age of onset (p < 0.001), shorter stature (p < 0.001), higher rates of lower limb deformity (p < 0.001), joint laxity (p = 0.041), anterior beaking of the vertebra and irregular/flared metaphysis (p < 0.001), while lower rate of joint pain/osteoarthritis (p < 0.001) and abnormal femoral head (p = 0.008). Missense variants in T3–4 and T3–5 were more likely to cause EDM1 (all p < 0.001), while those in T3–1 and T3–6 to T3–8 were associated with a greater frequency of PSACH (p = 0.002 to 0.023). Majority of in-frame variants were found in PSACH, as c.1417_1419del (p.Asp473del) being PSACH specific.

PSACH exhibits more severe phenotypes than EDM1, even with phenotypic overlap. In-frame variants are more strongly associated with PSACH, as the hotspot variant p.Asp473del exclusively identified in PSACH. In contrast, missense variants in T3–4 and T3–5 show a stronger association with EDM1.