Importance of Long-Term Follow-Up in the Prognosis of Mucopolysaccharidosis IV-A: A Case Report from Southwestern of Colombia

Abstract Mucopolysaccharidosis IV-A (MPS IV-A) is an autosomal recessive genetic disorder caused by a deficiency in the enzyme N-acetylgalactosamine-6-sulfatase, leading to the accumulation of chondroitin-6-sulfate (C6S) and keratan sulfate (KS). This is a rare disease, and, in Colombia, it is classified as an orphan disease under Resolution 023 of 2023. Notably, its incidence in Colombia is higher than that reported in other countries worldwide. Genomic analysis of the GALNS gene has identified more than 400 variants in affected individuals, enabling genotype-phenotype correlations. We report the case of a patient who was initially presented at the age of 5 with short stature, lower limb dysmetria, and genu valgum. Physical examination revealed coarse facial features, a short neck, pectus carinatum, multiple joint deformities, and ligamentous hyperlaxity. Enzymatic activity of GALNS was reported at 0.06 mmol/mL/hour, and complete sequencing of the GALNS gene was performed using next-generation sequencing (NGS) technology, identifying the homozygous variant c.239C>T (p.Ser80Leu), which is associated with MPS IV-A. A bioinformatic analysis classified this variant as pathogenic. This case underscores the importance of clinical presentation, the use of diagnostic methodologies, and confirmation through molecular and bioinformatic studies for an accurate and timely diagnosis, as well as the critical value of appropriate clinical follow-up.