Respiratory complications of metabolic disease in the paediatric population: A review of presentation, diagnosis and therapeutic options

Childhood Interstitial Lung Disease

Childhood interstitial lung disease (chILD) is a heterogeneous group of diseases with various clinical and imaging findings. The incidence and prevalence have increased in recent years, probably due to better comprehension of these rare diseases and increased awareness among physicians. chILDs present with nonspecific pulmonary symptoms, such as tachypnea, hypoxemia, cough, rales, and failure to thrive. Unnecessary invasive procedures can be avoided if specific mutations are detected through genetic examinations or if typical imaging patterns are recognized on computed tomography. Disease knowledge and targeted therapies are improving through international collaboration. Pulmonary involvement in systemic diseases is not uncommon. Pulmonary involvement may be the first finding in connective tissue diseases. This review aims to present a systematic patient-targeted approach to the diagnosis of chILD.

Tracheal Resection for Critical Airway Obstruction in Morquio A Syndrome

Introduction

The primary cause of death in Morquio A syndrome (mucopolysaccharidosis (MPS) IVA) is airway obstruction, brought about by an inexorable and pathognomonic multilevel airway tortuosity, buckling, and obstruction. The relative pathophysiological contributions of an inherent cartilage processing defect versus a mismatch in longitudinal growth between the trachea and the thoracic cage are currently a subject of debate. Enzyme replacement therapy (ERT) and multidisciplinary management continue to improve life expectancy for Morquio A patients by slowing many of the multisystem pathological consequences of the disease but are not as effective at reversing established pathology. An urgent need has developed to consider alternatives to palliation of progressive tracheal obstruction to preserve and maintain these patients' hard-won good quality of life, as well as to facilitate spinal and other required surgery. Case Report. Following multidisciplinary discussion, transcervical tracheal resection with limited manubriectomy was successfully performed, without the need for cardiopulmonary bypass, in an adolescent male on ERT with the severe airway manifestations of Morquio A syndrome. His trachea was found to be under significant compressive forces at surgery. On histology, chondrocyte lacunae appeared enlarged, but intracellular lysosomal staining and extracellular glycosaminoglycan staining was comparable to control trachea. At 12 months, this has resulted in a significant improvement in respiratory and functional status, with corresponding enhancement to his quality of life.

Conclusion

This addressing of tracheal/thoracic cage dimension mismatch represents a novel surgical treatment approach to an existing clinical paradigm and may be useful for other carefully selected individuals with MPS IVA. Further work is needed to better understand the role and optimal timing of tracheal resection within this patient cohort so as to individually balance considerable surgical and anaesthetic risks against the potential symptomatic and life expectancy benefits.

Data in support of the longitudinal characterization of pulmonary function in children with Mucopolysaccharidoses IVA

Mucopolysaccharidoses type IVA (Morquio disease) is a rare, autosomal recessive lysosomal storage disease that causes both obstructive and restrictive airway pathology, with respiratory failure being the primary cause of death. This article provides original data on the longitudinal characterization of pulmonary function changes in children with Mucopolysaccharidoses (MPS) IVA by presenting the data and nuanced trends of changes from sequential spirometry and oximetry. The sample size included 16 subjects, 13 had undergone enzyme replacement therapy (ERT), three had not undergone ERT treatment. A total of 180 individual plots are presented for spirometry variables (FEV1, FEV1 [%Pred] FVC, FVC [%Pred] and FEV1/FVC), 6MWT and oximetry variables (median %Spo2, ODI 3%, mean nadir 3%, ODI 4%, mean nadir 4% and min dip SpO2 [%]); over a nine-year period at a single quaternary paediatric metabolic centre. This data has been made public and has utility to clinicians and researchers due to the following: [1,2] by providing the first comprehensive report of detailed changes in pulmonary function in children with MPS IVA, with and without ERT; [1-3] as well as changes in pulmonary function following the institution of non-invasive ventilation (NIV) and adenotonsillectomy. The data presented is related to the research article by Kenth et al. "The Characterization of Pulmonary Function in Patients with Mucopolysaccharidoses IVA: A Longitudinal Analysis".

The characterisation of pulmonary function in patients with mucopolysaccharidoses IVA: A longitudinal analysis

Introduction

Mucopolysaccharidosis (MPS) type IVA is a rare, autosomal recessive lysosomal storage disease causing substrate accumulation in various organs and tissues. MPS IVA is associated with both obstructive and restrictive airway disease, with the former often resulting in sleep disordered breathing (SDB). Respiratory failure is a primary cause of death in this condition. The aim of this study was to characterise and catalogue the long-term respiratory changes in patients with MPS IVA treated with, or without, enzyme replacement therapy (ERT).

Methods

In this retrospective, longitudinal, repeated-measures cohort study, descriptive statistics and non-parametric correlation were performed for demographic, respiratory function and oximetry variables over a study period from January 2009 to December 2018. Composite clinical endpoints used in this study for evaluating pulmonary function included spirometry variables (FEV₁, FEV₁ [%Pred] FVC, FVC [%Pred] and FEV1/FVC), oximetry variables (median %Spo2, ODI 3%, mean nadir 3%, ODI 4%, mean nadir 4% and min dip SpO2 [%]) and 6MWT to assess functional exercise capacity and thus integrated cardiopulmonary function.

Results

Sequential spirometry and oximetry values were collected from 16 patients, of which 13/16 were ERT treated. In general, during the study period there was a global reduction in static spirometry values in all subjects, as well as cardiorespiratory function as assessed by the 6MWT, with the decline being delayed in the ERT group. Oximetry changed to a minor degree over time in the ERT group, whereas it declined in the non-ERT group. FEV₁, FVC [%predicted] and ODI 3% exhibited a strong, combined positive correlation (r 0.74–95% CI 0.61 to 0.83; p < .0001). Non-invasive ventilation (NIV) and adenotonsillectomy appeared more effective in the ERT group, either improving pulmonary function or attenuating deterioration.

Conclusions

Whilst spirometry values showed a gradual decline across all groups, oximetry showed modest improvement in respiratory function. The amalgamation of FEV₁, FVC [%predicted] and ODI 3% appeared predictive of changes in respiratory function in this study, suggestive as being composite endpoints for monitoring disease progression as well as guiding response to ERT in MPS IVA patients.