Diagnostic Quest of a Patient with a Mild Form of Mucopolysaccharidosis, Type I (Scheie Syndrome): Case Study

Background. Diagnosis of mild forms of mucopolysaccharidosis (MPS) causes significant difficulties, and its untimely recognition delays pathogenetic therapy initiation. Case description . Girl Ya., was consulted by neurologist at the age of 6 months due to delayed motor development. Umbilical hernia was diagnosed at the age of 1 year, appearance of fine motor disorders, adenoid hypertrophy and hearing impairment were noted at the age of 3 years, elbow and knee stiffness, gait disturbance, fatigue, exertional dyspnea, and corneal opacity — at 4 years, myelopathy of cervical spinal cord with flail hands paraparesis, external hydrocephalus, flexion elbow contractures, varus feet deformity, and bilateral tubotitis were diagnosed in the hospital at the age of 5. She was examined by a geneticist for а first at the age of 8, disease from the MPS group was suspected. Decreasein arylsulfatase B activity (1.8 nM/mg/h) (reference values 42.8–129.8 nM/mg/h) and dermatan sulfate excretion were revealed, thus, MPS, type VI was suspected. Full sequencing of the ARSB gene was performed, no pathogenic or probably pathogenic variants were revealed. Arylsulfatase activity was within the reference values during the next analysis, however dramatic decrease in a-L-iduronidase activity was detected — up to 0.001 μM/L/h (reference values 1–25 μM/L/h). Pathogenic variant c.208C> T (p.Gln70*) was revealed in exon 2 of the IDUA gene, as well as variant of unknown clinical value c.1505G> C (p.Arg502Pro) in exon 10, both in a heterozygous state. The patient was diagnosed with mucopolysaccharidosis, type I (Scheie syndrome). Pathogenetic (enzyme replacement) therapy was initiated, its results were followed-up until the age of 17 years old. Conclusion . Early diagnosis of MPS is crucial for timely pathogenetic treatment initiation, as it can significantly improve the prognosis for mild forms of the disease.