Investigations and treatment
At 3 years of age, the patient was seen at the genetics service of the Child’s Health Specialized Institute (Instituto Especializado de Salud del Niño ) where metabolic screening tests with cetyltrimethylammonium bromide and toluidine blue were positive for GAGs in the urine, and fluorometric quantification of N-acetylgalactosamine 4 sulfatase in blood (carried out in Germany) showed a result of 20.8 µmol/l/h (normal reference values > 50 µmol/l/h).ASB sequencing (preformed at Centogene, Rostock, Germany) showed a homozygous deletion covering exons 7 and 8, which was confirmed by qPCR and corroborates diagnosis of MPS VI.
Based on these findings, a deficiency of N-acetylgalactosamine 4 sulfatase (MPS VI) was diagnosed and the patient was referred to the Central Military Hospital for enzyme replacement treatment with galsulfase. The physical examination showed a patient 3 years and 6 months of age with global growth and developmental delay (z score -0.88 for weight and -2.83 for height); head circumference greater than the 95th percentile; genu valgum associated with generalized joint stiffness and contractures; brachydactyly, claw hands, trigger finger, loss of fine motor skills; corneal opacity; small and spaced-out teeth; reducible umbilical hernia, and hepatomegaly (Figure 2).
Assessment by a multidisciplinary team found mild glaucoma, allergic rhinitis and bilateral otitis media; carpal syndrome-like bilateral median nerve neuropathy, predominantly of the left side; mild obstructive hypopnea; cranial hyperostosis; corrected acetabular dysplasia (history of surgically corrected coxa valga); vertebral narrowing with subluxation and kyphoscoliosis; hepatosplenomegaly; microcephaly with non-communicating hydrocephalus; and spinal cord compression at L1-L2 and C5-C6.
Based on these findings, enzyme replacement therapy with galsulfase (N-acetylgalactosamine 4 sulfatase) 1 mg/kg/week was initiated at 3 years 6 months of age. The patient was followed for 6 years and 4 months at the institution, with no evidence of drug-related adverse events.