Morquio A syndrome and effect of enzyme replacement therapy in different age groups of Turkish patients: a case series

Identification of Surrogate Biomarkers for Mucopolysaccharidosis Type IVA

Mucopolysaccharidosis type IVA (MPS IVA, Morquio A syndrome) is a rare inherited disorder characterized by skeletal dysplasia due to deficient N-acetylgalactosamine-6-sulfate sulfatase activity, resulting in glycosaminoglycan (GAG) accumulation. Identifying accurate biomarkers reflecting clinical severity and therapeutic response remains challenging. This study evaluated potential surrogate biomarkers, including N-terminal pro-C-type natriuretic peptide (NT-proCNP), collagen types I and II, mono-sulfated keratan sulfate (KS), di-sulfated KS, and chondroitin-6-sulfate (C6S), in blood and urine samples from 60 patients ranging from 1 to 62 years of age. NT-proCNP levels were significantly elevated in patients of all ages and negatively correlated with growth impairment, especially after 8 years of age. Collagen type I levels significantly increased in adult patients, whereas collagen type II showed age-dependent elevations. Urinary KS, in mono- and di-sulfated forms, demonstrated moderate negative correlations with growth impairment. Moreover, NT-proCNP, mono- and di-sulfated KS in plasma, and urinary di-sulfated KS were not affected by enzyme replacement therapy in patients younger than 12 years, unlike urinary mono-sulfated KS. In conclusion, NT-proCNP has emerged as a promising independent biomarker reflecting the severity of skeletal dysplasia and possibly the near-future growth rate. These findings highlight the potential role of NT-proCNP in clinical assessment and monitoring therapeutic efficacy, addressing current unmet needs in MPS IVA management.

Hearing loss in patients with Morquio A syndrome: A scoping review

BACKGROUND

Hearing impairment is a prevalent clinical feature in Morquio syndrome (mucopolysaccharidosis IVA or MPS IVA) patients, often presenting in diverse forms: conductive, sensorineural, or a combination known as mixed hearing loss. The mixed form entails a blend of both conductive and sensorineural elements, typically exhibiting a progressive trajectory. This scoping review aimed to comprehensively analyze available evidence pertaining to the pathophysiology, classification, epidemiology, and clinical management of hearing loss in individuals with MPS IVA.

METHODS

Targeted literature was searched using MEDLINE, Literatura Latino-Americana e do Caribe em Ciências da Saúde, Web of Science, the Cochrane Library, Trip Medical Database, Embase, ScienceDirect, and Google Scholar, with a second search cycle to identify gray literature. A systematic search strategy using Medical Subject Headings keywords was implemented: "Hearing Disorders" OR "Hearing Loss" AND "Mucopolysaccharidosis IV" or "Hearing Disorders" OR "Hearing Loss" AND "Mucopolysaccharidosis IV." The identified bibliography was uploaded to COVIDENCE platform for information management. Articles were screened by 3 independent reviewers following the eligibility criteria.

RESULTS

Twenty-seven articles met the inclusion criteria, spanning information from 568 patients across 16 different countries. None of the studies had complete epidemiological information. Only 2 studies provided sufficient data to address the pathophysiology, while 3 addressed management and treatment. Hearing loss was reported in 210 of 568 patients. A total of 19.2% of patients reported recurrent ear infections. None of the studies reported vertigo, tinnitus, or dizziness in the patients. Pure-tone audiometry was the primary test used to diagnose and monitor auditory impairment in patients with Morquio syndrome.

CONCLUSIONS

Five hundred sixty-eight patients with MPS IVA were identified, of whom 210 (37%) developed hearing loss, the most common of which was moderate. Despite the lack of information on the diagnosis and management of hearing loss in Morquio syndrome, this study found that approximately one-third of participants exhibited some form of auditory impairment, with the majority of these cases being sensorineural in nature.

Adeno-Associated Virus Gene Transfer Ameliorates Progression of Skeletal Lesions in Mucopolysaccharidosis IVA Mice

Mucopolysaccharidosis type IVA (MPS IVA) is an autosomal congenital metabolic lysosomal disease caused by a deficiency of the N-acetyl-galactosamine-6-sulfate sulfatase (GALNS) gene, leading to severe skeletal dysplasia. The available therapeutics for patients with MPS IVA, enzyme replacement therapy and hematopoietic stem cell transplantation, revealed limitations in the impact of skeletal lesions. Our previous study, a significant leap forward in MPS IVA research, showed that liver-targeted adeno-associated virus (AAV) gene transfer of human GALNS (hGALNS) restored GALNS enzymatic activity in blood and multiple tissues and partially improved the aberrant accumulation of storage materials. This promising approach was further validated in our current study, where we delivered AAV8 vectors expressing hGALNS, under the control of a liver-specific or ubiquitous promoter, into MPS IVA murine disease models. The results were highly encouraging, with both AAV8 vectors leading to supraphysiological enzymatic activity in plasma and improved cytoplasmic vacuolization of chondrocytes in bone lesions of MPS IVA mice. Notably, the ubiquitous promoter constructs, a potential game-changer, resulted in significantly greater enzyme activity levels in bone and improved pathological findings of cartilage lesions in these mice than in a liver-specific one during the 12-week monitoring period, reinforcing the positive outcomes of our research in MPS IVA treatment.

Clinical characteristics and effects of enzyme replacement therapy with elosulfase alfa in Korean patients with mucopolysaccharidosis type IVA

Mucopolysaccharidosis type IVA (MPS IVA) is a rare autosomal recessive disorder caused by a deficiency in N-acetylgalactosamine-6-sulfatase, which results in skeletal and connective tissue abnormalities, as well as various non-skeletal manifestations. Although enzyme replacement therapy (ERT) is recommended as the first-line treatment, the outcomes of ERT on bone pathology remain controversial. We report clinical characteristics and outcomes of ERT in 9 patients with MPS IVA (6 males and 3 females) from 7 unrelated families. During ERT, results from pulmonary function tests, echocardiography, the 6-min walk test, and the Functional Independence Measure were monitored biannually. Anthropometric data were compared with previously reported growth charts of subjects with MPS IVA.

Among the 9 patients (5 severe, and 4 slowly progressive form), 7 patients (5 severe, 2 slowly progressive) commenced ERT at a median age of 3.8 years (range: 0.8–13.7 years) and were treated for a median duration of 1.9 years (range: 1.2–5.7 years). Mean height standard deviation scores using MPS IVA growth charts were + 0.4 (+0.0 in severe phenotypes) at initiation and + 0.7 (+0.2 in severe phenotypes) at the last follow-up. Four patients with severe phenotypes underwent surgery for cervical myelopathy and 1 patient with a slowly progressive phenotype underwent a bilateral pelvic osteotomy for hip pain during ERT. The parameters of pulmonary and heart function, endurance, and Functional Independence Measure scores were maintained or increased after ERT. Overall, ERT was well tolerated without deterioration of cardiorespiratory and functional outcomes during treatment, although skeletal outcomes, including growth, were limited.

Mucopolysaccharidosis Type IVA: Extracellular Matrix Biomarkers in Cardiovascular Disease

Cardiovascular disease (CVD) in Mucopolysaccharidosis Type IVA (Morquio A), signified by valvular disease and cardiac hypertrophy, is the second leading cause of death and remains untouched by current therapies. Enzyme replacement therapy (ERT) is the gold-standard treatment for MPS disorders including Morquio A. Early administration of ERT improves outcomes of patients from childhood to adulthood while posing new challenges including prognosis of CVD and ERT's negligible effect on cardiovascular health. Thus, having accurate biomarkers for CVD could be critical. Here we show that cathepsin S (CTSS) and elastin (ELN) can be used as biomarkers of extracellular matrix remodeling in Morquio A disease. We found in a cohort of 54 treatment naïve Morquio A patients and 74 normal controls that CTSS shows promising attributes as a biomarker in young Morquio A children. On the other hand, ELN shows promising attributes as a biomarker in adolescent and adult Morquio A. Plasma/urine keratan sulfate (KS), and urinary glycosaminoglycan (GAG) levels were significantly higher in Morquio A patients (p < 0.001) which decreased with age of patients. CTSS levels did not correlate with patients' phenotypic severity but differed significantly between patients (median range 5.45-8.52 ng/mL) and normal controls (median range 9.61-15.9 ng/mL; p < 0.001). We also studied α -2-macroglobulin (A2M), C-reactive protein (CRP), and circulating vascular cell adhesion molecule-1 (sVCAM-1) in a subset of samples to understand the relation between ECM biomarkers and the severity of CVD in Morquio A patients. Our experiments revealed that CRP and sVCAM-1 levels were lower in Morquio A patients compared to normal controls. We also observed a strong inverse correlation between urine/plasma KS and CRP (p = 0.013 and p = 0.022, respectively) in Morquio A patients as well as a moderate correlation between sVCAM-1 and CTSS in Morquio A patients at all ages (p = 0.03). As the first study to date investigating CTSS and ELN levels in Morquio A patients and in the normal population, our results establish a starting point for more elaborate studies in larger populations to understand how CTSS and ELN levels correlate with Morquio A severity.