Tracheal narrowing in children and adults with mucopolysaccharidosis type IVA: evaluation with computed tomography angiography

Molecular therapy and nucleic acid adeno-associated virus-based gene therapy delivering combinations of two growth-associated genes to MPS IVA mice

Mucopolysaccharidosis type IVA (MPS IVA) is caused by a deficiency of the galactosamine (N-acetyl)-6-sulfatase (GALNS) enzyme responsible for the degradation of specific glycosaminoglycans (GAGs). The progressive accumulation of GAGs leads to various skeletal abnormalities (short stature, hypoplasia, tracheal obstruction) and several symptoms in other organs. To date, no treatment is effective for patients with bone abnormalities. To improve bone pathology, we propose a novel combination treatment with the adeno-associated virus (AAV) vectors expressing GALNS enzyme and a natriuretic peptide C (CNP; NPPC gene) as a growth-promoting agent for MPS IVA. In this study, an MPS IVA mouse model was treated with an AAV vector expressing GALNS combined with another AAV vector expressing NPPC gene, followed for 12 weeks. After the combination therapy, bone growth in mice was induced with increased enzyme activity in tissues (bone, liver, heart, lung) and plasma. Moreover, there were significant changes in bone morphology in CNP-treated mice with increased CNP activity in plasma. Delivering combinations of CNP and GALNS gene therapies enhanced bone growth in MPS IVA mice more than in GALNS gene therapy alone. Enzyme expression therapy alone fails to reach the bone growth region; our results indicate that combining it with CNP offers a potential alternative.

Tracheal Narrowing and Its Impact on Anesthesia Care in Patients With Morquio A (Mucopolysaccharidosis Type IVA): An Observational Study

BACKGROUND

Recently, tracheal narrowing has been recognized as a significant comorbid condition in patients with Morquio A, also known as mucopolysaccharidosis IVA. We studied a large cohort of patients with Morquio A to describe the extent of their tracheal narrowing and its relationship to airway management during anesthesia care.

METHODS

This is an observational study, collecting data retrospectively, of a cohort of patients with Morquio A. Ninety-two patients with Morquio A syndrome were enrolled, among whom 44 patients had their airway evaluated by computed tomography angiography and had undergone an anesthetic within a year of the evaluation. Our hypothesis was that the tracheal narrowing as evaluated by computed tomography angiography increases with age in patients with Morquio A. The primary aim of the study was to examine the degree of tracheal narrowing in patients with Morquio A and describe the difficulties encountered during airway management, thus increasing awareness of both the tracheal narrowing and airway management difficulties in this patient population. In addition, the degree of tracheal narrowing was evaluated for its association with age or spirometry parameters using Spearman's rank correlation. Analysis of variance followed by the Bonferroni test was used to further examine the age-based differences in tracheal narrowing for the 3 age groups: 1 to 10 years, 11 to 20 years, and >21 years.

RESULTS

Patient age showed a positive correlation with tracheal narrowing ( rs= 0.415; 95% confidence interval [95% CI], 0.138-0.691; P = .005) with older patients having greater narrowing of the trachea. Among spirometry parameters, FEF25%-75% showed an inverse correlation with tracheal narrowing as follows: FEF25%-75% versus tracheal narrowing: ( rs = -0.467; 95% CI, -0.877 to -0.057; P = .007). During anesthetic care, significant airway management difficulties were encountered, including cancelation of surgical procedures, awake intubation using flexible bronchoscope, and failed video laryngoscopy attempts.

CONCLUSIONS

Clinically significant tracheal narrowing was present in patients with Morquio A, and the degree of such narrowing likely contributed to the difficulty with airway management during their anesthetic care. Tracheal narrowing worsens with age, but the progression appears to slow down after 20 years of age. In addition to tracheal narrowing, spirometry values of FEF25%-75% may be helpful in the overall evaluation of the airway in patients with Morquio A.

Endoscopic and Image Analysis of the Airway in Patients with Mucopolysaccharidosis Type IVA

Mucopolysaccharidosis (MPS) is a hereditary disorder arising from lysosomal enzymes deficiency, with glycosaminoglycans (GAGs) storage in connective tissues and bones, which may compromise the airway. This retrospective study evaluated patients with MPS type IVA with airway obstruction detected via endoscopy and imaging modalities and the effects of surgical interventions based on symptoms. The data of 15 MPS type IVA patients (10 males, 5 females, mean age 17.8 years) were reviewed in detail. Fiberoptic bronchoscopy (FB) was used to distinguish adenotonsillar hypertrophy, prolapsed soft palate, secondary laryngomalacia, vocal cord granulation, cricoid thickness, tracheal stenosis, shape of tracheal lumen, nodular deposition, tracheal kinking, tracheomalacia with rigid tracheal wall, and bronchial collapse. Computed tomography (CT) helped to measure the deformed sternal angle, the cross-sectional area of the trachea, and its narrowest/widest ratio (NW ratio), while angiography with 3D reconstruction delineated tracheal torsion, kinking, or framework damage and external vascular compression of the trachea. The NW ratio correlated negatively with age (p < 0.01), showing that airway obstruction progressed gradually. Various types of airway surgery were performed to correct the respiratory dysfunction. MPS type IVA challenges the management of multifactorial airway obstruction. Preoperative airway evaluation with both FB and CT is strongly suggested to assess both intraluminal and extraluminal factors causing airway obstruction.

Anesthetic Concerns of Children With Skeletal Dysplasia

Children with skeletal dysplasia present unique challenges for safe anesthetic care including differences in the anatomy of the respiratory system, possibility of cervical spine instability or spinal stenosis, and a unique body habitus. Even seemly routine anesthesia can result in respiratory arrest or spinal cord injury. These complications can largely be avoided by proper planning such as appropriate techniques for the intubation of difficult airways, recognition of cervical instability, neuromonitoring for any anesthesia over an hour in patients with severe spinal stenosis, and preoperative assessment of the trachea and avoidance of neuraxial anesthesia in children with Morquio syndrome.

Activity of daily living in mucopolysaccharidosis IVA patients: Evaluation of therapeutic efficacy

Background

Mucopolysaccharidosis IVA (MPS IVA, also called Morquio A syndrome) is caused by a deficiency of N‐acetylglucosamine‐6‐sulfate sulfatase (GALNS) and results in skeletal dysplasia symptoms such as short stature and abnormal gait. Treatments include enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT), but the effects are limited depending on the age of initiation and clinical phenotype. Thus, this study aims to assess the effects of treatments on MPS IVA patients compared to untreated MPS IVA patients and an age‐matched control group.

Methods

We used activity of daily living (ADL) survey with 4 sections: “movement,” “movement with cognition,” “cognition,” and “other MPS symptoms.” Lower scores indicate more assistance required. This study included 161 patients, 270 total surveys, and 70 patients with longitudinal data.

Results

We describe 134 severe patients and 25 attenuated patients. ERT and HSCT treatment improved only the “other MPS symptoms” section in severe patients. There were no differences between ERT and HSCT severe patient scores. A 19‐year‐old male patient, who had robust physical training, provided a significant increase in “movement” without treatment, suggesting the importance of exercise.

Conclusion

Overall, this ADL questionnaire has demonstrated validation and reliability in assessing the MPS IVA patients and therapeutic efficacy.

Disease Manifestations in Mucopolysaccharidoses and Their Impact on Anaesthesia-Related Complications-A Retrospective Analysis of 99 Patients

Patients with mucopolysaccharidoses (MPS) frequently require anaesthesia for diagnostic or surgical interventions and thereby experience high morbidity. This study aimed to develop a multivariable prediction model for anaesthesia-related complications in MPS. This two-centred study was performed by retrospective chart review of children and adults with MPS undergoing anaesthesia from 2002 until 2018. We retrieved the patients’ demographics, medical history, clinical manifestations, and indication by each anaesthesia. Multivariable mixed-effects logistic regression was calculated for a clinical model based on preoperative predictors preselected by lasso regression and another model based on disease subtypes only. Of the 484 anaesthesia cases in 99 patients, 22.7% experienced at least one adverse event. The clinical model resulted in a better forecast performance than the subtype-model (AICc 460.4 vs. 467.7). The most relevant predictors were hepatosplenomegaly (OR 3.10, CI 1.54–6.26), immobility (OR 3.80, CI 0.98–14.73), and planned major surgery (OR 6.64, CI 2.25–19.55), while disease-specific therapies, i.e., haematopoietic stem cell transplantation (OR 0.45, CI 0.20–1.03), produced a protective effect. Anaesthetic complications can best be predicted by surrogates for advanced disease stages and protective therapeutic factors. Further model validation in different cohorts is needed.

Automated Assessment of Thoracic-Abdominal Asynchrony in Patients with Morquio Syndrome

Morquio syndrome is a rare disease caused by a disorder in the storage of mucopolysaccharides that affects multiple organs, including musculoskeletal, respiratory, cardiovascular, and digestive systems. Respiratory failure is one of the leading causes of mortality in Morquio patients; thus, respiratory function testing is vital to the management of the disease. An automated respiratory assessment methodology using the pneuRIP device and a machine-learning algorithm was developed. pneuRIP is a noninvasive approach that uses differences between thoracic and abdominal movements (thoracic-abdominal asynchrony) during respiration to assess respiratory status. The technique was evaluated on 17 patients with Morquio (9 females and 8 males) between the ages of 2 and 57 years. The results of the automated technique agreed with the clinical assessment in 16 out of the 17 patients. It was found that the inverse cumulative percentage representation of the time delay between the thorax and abdomen was the most critical variable for accurate evaluation. It was demonstrated that the technique could be successfully used on patients with Morquio who have difficulty breathing with 100% compliance. This technique is highly accurate, portable, noninvasive, and easy to administer, making it suitable for a variety of settings, such as outpatient clinics, at home, and emergency rooms.