Novel mutation in HPRT1 causing a splicing error with multiple variations

Case report: Whole exome sequencing identifies a novel variant in the HPRT1 gene in a male with developmental delay

Lesch-Nyhan syndrome (LNS, OMIM #300322) is a rare X-linked genetic disorder caused by variants in the HPRT1 gene, which codes for the Hypoxanthine-guanine phosphoribosyltransferase (HGPRT). HPRT1 gene variants disrupt normal purine metabolism, leading to the involvement of multiple organ systems, primarily characterized by hyperuricemia, dystonia, and neurological abnormalities, which makes LNS clinically heterogeneous and diagnostically challenging. Here, we report a rare case of a 27-year-old Chinese male exhibiting severe lower limb motor disorders, hyperuricemia, and intellectual development delay. Blood tests showed hyperuricemia and whole exome sequencing (WES) identified a novel hemizygous variant in the HPRT1 (NM-000194.3) gene: c.104T > C in exon 2, respectively. Bioinformatics techniques indicated that the variant may disrupt the activity of HGPRT. According to the clinical presentation, diagnostic examination, and WES results, the patient was finally diagnosed with LNS. This study identified a previously unreported pathogenic variant in the HPRT1 gene. Although no curative therapy is currently available for HPRT1 gene variants at present, a definite diagnosis of its genetic etiology is of great significance for genetic counseling and family planning.

Catching the Culprit: How Chorea May Signal an Inborn Error of Metabolism

Background

Movement disorders, particularly chorea, are uncommon in inborn errors of metabolism, but their identification is essential for improved clinical outcomes. In this context, comprehensive descriptions of movement disorders are limited and primarily derived from single cases or small patient series, highlighting the need for increased awareness and additional research in this field.

Methods

A systematic review was conducted using the MEDLINE database and GeneReviews. The search included studies on inborn errors of metabolism associated with chorea, athetosis, or ballismus. The review adhered to PRISMA guidelines.

Results

The systematic review analyzed 76 studies out of 2350 records, encompassing the period from 1964 to 2022. Chorea was observed in 90.1% of the 173 patients, followed by athetosis in 5.7%. Various inborn errors of metabolism showed an association with chorea, with trace elements and metals being the most frequent. Cognitive and developmental abnormalities were common in the cohort. Frequent neurological features included seizures, dysarthria, and optic atrophy, whereas non-neurological features included, among others, facial dysmorphia and failure to thrive. Neuroimaging and biochemical testing played crucial roles in aiding diagnosis, revealing abnormal findings in 34.1% and 47.9% of patients, respectively. However, symptomatic treatment efficacy for movement disorders was limited.

Discussion

This study emphasizes the complexities of chorea in inborn errors of metabolism. A systematic approach with red flags, biochemical testing, and neuroimaging is required for diagnosis. Collaboration between neurologists, geneticists, and metabolic specialists is crucial for improving early detection and individualized treatment. Utilizing genetic testing technologies and potential therapeutic avenues can aid in the improvement of patient outcomes.