# Two case reports and a literature review of hyperphosphatasia with intellectual disability syndrome 2 caused by a PIGO mutation

## TL;DR

This paper reports two new cases of a rare genetic disorder caused by mutations in the PIGO gene and expands understanding of its symptoms and genetic variations.

## Contribution

The study identifies novel PIGO gene mutations and expands the phenotypic spectrum of HPIDS2 through two new clinical cases.

## Key findings

- Compound heterozygous PIGO gene mutations were found in two HPIDS2 patients.
- Novel mutations c.[2510T>A] and c.[693C>G] were identified in the PIGO gene.
- Alkaline phosphatase levels may indicate disease severity and prognosis in HPIDS2.

## Abstract

This study investigates the clinical features and genetic mutations associated with hyperphosphatasia with impaired intellectual development syndrome-2 (HPIDS2).

A retrospective analysis was performed on two HPIDS2 cases treated at the Department of Rehabilitation, Nanjing Children's Hospital, from 2019 to 2023. Clinical features and genetic characteristics were summarized through a literature review.

Genetic testing showed compound heterozygous variations in the PIGO gene for both patients (Patient 1: c.[2612A>C];[2361dup]; Patient 2: c.[2510T>A];[693C>G]), with c.[2510T>A] and c.[693C>G] identified as novel mutations.

Global developmental delay, with or without hyperphosphatemia, may indicate HPIDS2. The level of alkaline phosphatase elevation could reflect disease severity and prognosis. Our cases expand the known pathogenic variations in the PIGO gene and phenotypic spectrum of HPIDS2.