Maroteaux-Lamy syndrome (MPS-VI) is a rare autosomal-recessive disorder with a wide spectrum of clinical manifestations, ranging from an attenuated to a rapidly progressive disease. It is caused by variants in ARSB, which encodes the lysosomal arylsulfatase B (ARSB) enzyme, part of the degradation process of glycosaminoglycans in lysosomes. Over 220 variants have been reported so far, with a majority of missense variants. We hereby report two siblings of Bedouin origin with a diagnosis of MPS-VI. Western blots in patient fibroblasts revealed total absence of ARSB protein production. Complete sequencing of the coding region of ARSB did not identify a candidate disease-associated variant. However, deep sequencing of the noncoding region of ARSB by whole genome sequencing (WGS) revealed a c.1142+581A to G variant. The variant is located within intron 5 and fully segregated with the disease in the family. Determination of the genetic cause for these patients enabled targeted treatment by enzyme replacement therapy, along with appropriate genetic counseling and prenatal diagnosis for the family. These results highlight the advantage of WGS as a powerful tool, for improving the diagnostic rate of rare disease-causing variants, and emphasize the importance of studying deep intronic sequence variation as a cause of monogenic disorders.

MPS disorders are associated with a wide spectrum of neurocognitive effects, from mild problems with attention and executive functions to progressive and degenerative neuronopathic disease. Studies of the natural history of neurocognition are necessary to determine the profile of abnormality and the rates of change, which are crucial to select endpoints for clinical trials of brain treatments and to make clinical recommendations for interventions to improve patients' quality of life. The goal of this paper is to review neurocognitive natural history studies to determine the current state of knowledge and assist in directing future research in all MPS disorders. There are seven different types of MPS diseases, each resulting from a specific enzyme deficiency and each having a separate natural history. MPS IX, will not be discussed as there are only 4 cases reported in the literature without cognitive abnormality. For MPS IH, hematopoietic cell transplant (HCT) is standard of care and many studies have documented the relationship between age at treatment and neurocognitive outcome, and to a lesser extent, neurocognitive status at baseline. However, the mortality and morbidity associated with the transplant process and residual long-term problems after transplant, have led to renewed efforts to find better treatments. Rather than natural history, new trials will likely need to use the developmental trajectories of the patients with HCT as a comparators. The literature has extensive data regarding developmental trajectories post-HCT. For attenuated MPS I, significant neurocognitive deficits have been documented, but more longitudinal data are needed in order to support a treatment directed at their attention and executive function abnormalities. The neuronopathic form of MPS II has been a challenge due to the variability of the trajectory of the disease with differences in timing of slowing of development and decline. Finding predictors of the course of the disease has only been partially successful, using mutation type and family history. Because of lack of systematic data and clinical trials that precede a thorough understanding of the disease, there is need for a major effort to gather natural history data on the entire spectrum of MPS II. Even in the attenuated disease, attention and executive function abnormalities need documentation. Lengthy detailed longitudinal studies are needed to encompass the wide variability in MPS II. In MPS IIIA, the existence of three good natural history studies allowed a quasi-meta-analysis. In patients with a rapid form of the disease, neurocognitive development slowed up until 42 to 47 months, halted up to about 54 months, then declined rapidly thereafter, with a leveling off at an extremely low age equivalent score below 22 months starting at about chronological age of 6. Those with slower or attenuated forms have been more variable and difficult to characterize. Because of the plethora of studies in IIIA, it has been recommended that data be combined from natural history studies to minimize the burden on parents and patients. Sufficient data exists to understand the natural history of cognition in MPS IIIA. MPS IIIB is quite similar to IIIA, but more attenuated patients in that phenotype have been reported. MPS IIIC and D, because they are so rare, have little documentation of natural history despite the prospects of treatments. MPS IV and VI are the least well documented of the MPS disorders with respect to their neurocognitive natural history. Because, like attenuated MPS I and II, they do not show progression of neurocognitive abnormality and most patients function in the range of normality, their behavioral, attentional, and executive function abnormalities have been ignored to the detriment of their quality of life. A peripheral treatment for MPS VII, extremely rare even among MPS types, has recently been approved with a post-approval monitoring system to provide neurocognitive natural history data in the future. More natural history studies in the MPS forms with milder cognitive deficits (MPS I, II, IV, and VI) are recommended with the goal of improving these patients' quality of life with and without new brain treatments, beyond the benefits of available peripheral enzyme replacement therapy. Recommendations are offered at-a-glance with respect to what areas most urgently need attention to clarify neurocognitive function in all MPS types.

Mucopolysaccharidosis type VI, also known as Maroteaux-Lamy syndrome, is an autosomal recessive lysosomal disorder, due to the deficiency of the enzyme arylsulfatase B that leads to the accumulation of dermatan sulfate in the tissues and its urinary excretion. Mucopolysaccharide deposition leads to a progressive disorder affecting multiple organs that often results in death at a young age. This disease has several oral manifestations, among which dental complications can be serious and include follicles similar to dentigerous cysts, malocclusions, condylar defects and gingival hyperplasia, in addition to a short neck, corneal opacity, macroglossia, skull enlargement, anteroposterior dimension long, claw hand is some of the clinical features. A case of a 14-month-old patient is presented, who attended a pediatric dentistry consultation for episodes of fever, low weight, severe gingival hyperplasia. Physical examination revealed coarse facies, short neck, pectus excavatus, hands with decreased grip, and neurodevelopmental delay. On intraoral examination, dental eruption delayed, generalized gingival hyperplasia, palate with little transverse growth. On radiographic examination, dental organs included and poor position in the anterior sector, upper molars within the maxillary sinus, rotated lower canines. He is referred to medicine for biochemical tests and genetics for diagnosis. Detailed biochemistry MPS type VI, confirmed by molecular testing. The clinical manifestations in this case correspond to the clinical form of rapid progression reported in these patients. They report: short stature, skeletal malformations and alterations at the oral level. Children with severe MPS VI start early and progress rapidly, bone radiographs and urine GAG measurement are helpful for diagnosis with genetic and ARSB enzyme activity. It is necessary to strengthen the knowledge in dentistry and the general population about the clinical characteristics of type VI mucopolysaccharides in order to have an early diagnosis and management of pathologies in these patients. La mucopolisacaridosis tipo VI, también conocida como síndrome de Maroteaux-Lamy, es un trastorno lisosómico autosómico recesivo, causado por la deficiencia de la enzima arilsulfatasa B, lo que conduce a la acumulación de dermatán sulfato en los tejidos y su excreción urinaria. La deposición de mucopolisacáridos genera un trastorno progresivo que afecta a múltiples órganos y que, a menudo, resulta en la muerte a temprana edad. Esta enfermedad tiene varias manifestaciones orales, entre las que destacan las complicaciones dentales, que pueden ser graves e incluir folículos similares a quistes dentígeros, maloclusiones, defectos condilares e hiperplasia gingival, además de características clínicas como cuello corto, opacidad corneal, macroglosia y agrandamiento del cráneo, dimensión anteroposterior larga y mano en garra. Se presenta el caso de un paciente de 14 meses de edad que acudió a consulta de odontopediatría por episodios de fiebre, bajo peso e hiperplasia gingival severa. El examen físico evidenció facies tosca, cuello corto, pectus excavatus, manos con disminución en agarre y retardo en el neurodesarrollo. El examen intraoral halló retardo de la erupción dental, hiperplasia gingival generalizada y paladar con poco crecimiento transversal. El examen radiográfico detectó órganos dentarios incluidos y mala posición en el sector anterior, molares superiores dentro del seno maxilar y caninos inferiores rotados. El paciente fue remitido a medicina para exámenes bioquímicos y genéticos para definir el diagnóstico. La bioquímica reveló MPS tipo VI, lo que fue confirmado mediante prueba molecular. Las manifestaciones clínicas en este caso corresponden a la forma clínica de progresión rápida reportada en estos pacientes: talla baja, malformaciones esqueléticas y alteraciones a nivel oral. Los niños con MPS VI grave comienzan temprano y progresan rápidamente, las radiografías óseas y la medición de GAG en orina son útiles para el diagnóstico con actividad de la enzima ARSB y genética. Es necesario fortalecer el conocimiento en odontología y la población en general sobre las características clínicas de mucopolisacáridos tipo VI para tener un diagnóstico temprano y un mejor manejo de patologías en estos pacientes.

Patients with mucopolysaccharidosis type VI (MPS VI) present with a wide range of disease severity and clinical manifestations, with significant functional impairment and shortened lifespan. Enzyme replacement therapy (ERT) with galsulfase has been shown to improve clinical and biochemical parameters including patient survival, quality of life and growth. The present study is a resurvey of 34 Brazilian MPS VI patients with rapidly progressive disease (classical phenotype) who initiated ERT with galsulfase under five years of age and had been on ERT until data collection in 2019, with few exceptions (n = 4 patients who died before 2019). Anthropometric measures, urinary glycosaminoglycans, and data regarding cardiac, orthopedic, neurologic, sleep apnea, hearing and ophthalmologic outcomes were filled in by specialists. Pubertal development, clinical complications, hospitalizations, and surgeries were also assessed. In this resurvey study, treatment with galsulfase has shown to be safe and well tolerated in MPS VI patients who initiated ERT under the age of 5 years and who have been undergoing ERT for approximately 10 years. Mortality rate suggests that early initiation of ERT may have a positive impact on patients' survival, improving but not preventing disease progression and death. MPS VI patients on ERT also showed improved growth velocity and the pubertal development was normal in all surviving patients. Follow-up data on pneumonia and hospitalization suggest that early ERT may have a protective effect against major respiratory complications. Cardiac valve disease progressed since their prior evaluation and spinal cord compression was observed in a large number of patients, suggesting that these disease complications were not modified by ERT.

The Mucopolysaccharidosis type VI (MPS VI), also known as Maroteaux-Lamy syndrome (OMIM 253200) is an autosomal recessive lysosomal disorder, caused by the deficiency of the enzyme N-acetylgalactosamine 4-sulfatase (also known as arylsulfatase B) due to mutations of the ARSB gene. Cardiologic features are well recognized, and are always present in MPS VI patients. Generally, the onset and the progression of the cardiologic symptoms are insidious, and just a few patients have developed a rapidly progressive disease. Cardiac involvement in MPS VI is a common and progressive feature. For MPS patients, cardiac evaluations are recommended every 1 to 2 years, including blood pressure measurement, electrocardiography and echocardiography. However, congestive heart failure and valvular surgical repair are not frequently seen, and if so, they are performed in adults. Here we report on an atypical MPS VI case with ascites fetalis and a rapidly progressive cardiac disease. A 6-month-old Brazilian male, only child of a Brazilian healthy non-consanguineous couple. During pregnancy, second trimester ultrasonography observed fetal ascites and bilateral hydrocele. Physical exam at 6 months-old revealed a typical gibbus deformity and MPS was suspected. Biochemical investigation revealed a diagnosis of MPS type VI, confirmed by molecular test. Baseline echocardiogram revealed discrete tricuspid regurgitation and a thickened mitral valve with posterior leaflet prolapse, causing moderate to severe regurgitation. The patient evolved with mitral insufficiency and congestive heart failure, eventually requiring surgical repair by the first year of age. We report the first case of MPS VI whose manifestations started in the prenatal period with fetal ascites, with severe cardiac valvular disease that eventually required early surgical repair. Moreover, in MPS with neonatal presentation, including fetal hydrops, besides MPS I, IVA and VII, clinicians should include MPS VI in the differential diagnosis.