# Juvenile Paget disease with unique compound heterozygous sequence variants in the TNFRSF11B gene

## TL;DR

This paper reports a rare case of Juvenile Paget disease in the Czech Republic with unique genetic variants in the TNFRSF11B gene, contributing to understanding of the disease and its treatment.

## Contribution

The study identifies unique compound heterozygous variants in TNFRSF11B in a JPD patient, expanding the genetic spectrum of this rare disease.

## Key findings

- A patient with JPD was found to have unique compound heterozygous TNFRSF11B variants.
- Early diagnosis and treatment improved the patient's quality of life and prevented further skeletal deformities.
- The findings enhance understanding of osteoprotegerin's role in skeletal and non-skeletal systems.

## Abstract

Juvenile Paget disease (JPD) is a rare autosomal recessive bone disease characterized by escalated bone metabolism leading to skeletal deformities, susceptibility to fractures, and some extraskeletal findings. This genetic disease is associated with changes in the TNFRSF11B gene encoding osteoprotegerin, an important regulator of osteoresorption. Most published JPD cases have been found to carry homozygous TNFRSF11B variants, while compound heterozygous variants in this gene have been reported only twice.

We report the first case of JPD diagnosed in the Czech Republic, who presented with a mild phenotype of this disease. The first bone fractures, appeared at 3 years of age. Other clinical manifestations included typical skeletal deformities, macrocephaly, arched chest, lower extremity valgosity, lateral bowing of the thighs, and anterior bowing of the shins. Minor mixed hearing impairment, angioid stripes of the choroidea, and temporary immunodeficiency were present among extra-skeletal findings. Sanger sequencing was performed on both the patient and the parents to test for the presence of TNFRSF11B sequence variants. Molecular genetic analysis showed unique compound heterozygous sequence variants in TNFRSF11B: a paternally inherited variant c.30 + 5G > A, p.(?) and a maternally inherited variant c.329G > T, p.(Gly110Val). Both of the variants were analyzed by several in silico predictive tools indicating, for their strongly supported pathogenicity according to American College of Medical Genetics and Genomics standards. Furthermore, we present diagnostic findings, their treatment, and follow-up care.

The newly described variants of TNFRSF11B extend knowledge of this very rare disease. Early diagnosis and antiresorption treatment prevent further fractures and deformity progression, and improve the patient’s quality of life. This example of osteoprotegerin deficiency may help us better understand its role in skeletal and non-skeletal systems.