Mucopolysaccharidosis VII in Brazil: natural history and clinical findings

BACKGROUND: Mucopolysaccharidosis type VII (MPS VII), also known as Sly syndrome, caused by deficiency of the lysosomal enzyme β-glucuronidase, is an ultra-rare disorder with scarce epidemiological data and few publications about natural history and clinical spectrum. METHODS: We conducted a case series report which included retrospective data from all MPS VII patients diagnosed through the “MPS Brazil Network” who were known to be alive in 2020 in Brazil (N = 13). Clinical data were obtained from a review of the medical records and descriptive statistics and variables were summarized using counts and percentages of the total population. RESULTS: The majority of the patients were from the Northeast region of Brazil. Among the signs and symptoms that raised the clinical suspicion of MPS, coarse face was the most frequent; 58% of the patients had a history of non-immune hydrops fetalis. All the subjects presented short neck and trunk. The majority presented typical phenotypical signs of MPS disorders. They all presented neurodevelopmental delay and cognitive impairment. About half of this cohort had knees deformities. Dysostosis multiplex was identified in almost all patients and cardiomyopathy was less frequent than observed in other types of MPSs. The mean age at diagnosis was 5 years, ranging from 1 to 14 years. Almost all patients (12/13) were homozygous for the c.526C>T (p.Leu176Phe) mutation. A novel variant of the GUSB gene was found, the c.875T>C (p.Leu292Pro), in a compound heterozygous with the c.526C>T (p.Leu176Phe) variant. CONCLUSIONS: This case series is the biggest data collection of MPS VII patients alive in Latin America. The overall clinical picture of the MPS VII patients is very similar to other MPS disorders, including a spectrum of severity and delayed diagnosis.