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Mucopolysaccharidoses: Complications and management

Author
Robert Wynn, MD, MRCP, FRCPath
Section Editors
Sihoun Hahn, MD, PhD
Marc C Patterson, MD, FRACP
Deputy Editor
Elizabeth TePas, MD, MS

INTRODUCTION

The mucopolysaccharidoses (MPS) are lysosomal storage disorders caused by the deficiency of enzymes required for the stepwise breakdown of glycosaminoglycans (GAGs), also known as mucopolysaccharides. These conditions are differentiated by their clinical features and age of presentation (table 1).

The complications associated with the MPS and their management are reviewed here. The clinical features and diagnosis of these disorders are discussed separately. (See "Mucopolysaccharidoses: Clinical features and diagnosis".)

RESPIRATORY COMPLICATIONS

Respiratory complications affect patients with all types of mucopolysaccharidoses (MPS) and contribute to death and disability as their disease progresses. Respiratory abnormalities result from airway obstruction, excessive secretions, skeletal restriction, organomegaly, frequent infections, and neurologic compromise [1,2]. These problems can lead to progressive respiratory insufficiency, severe sleep apnea, and sudden death from central apnea.

Central apnea from cord compression — MPS IV A and IV B patients are especially prone to high cord compression due to atlantoaxial instability and odontoid dysplasia, although this complication also occurs in other types. This condition may result in depressed respiration or sudden respiratory arrest [3-6]. Prophylactic cervical fusion is recommended in MPS IV patients and in other patients with cervical instability.

Airway obstruction — Patients with MPS I, II, VI, and VII often develop upper airway obstruction due to an enlarged tongue, thickened gums, and engorged soft tissues of the nasopharynx [1,2,7-10]. Increased tonsillar and adenoid size due to storage in lymphatic tissue also contributes to obstruction. Upper airway obstruction may be exacerbated in certain positions (eg, raising the arms may result in obstruction of the thoracic inlet, causing facial plethora, distension of the neck veins, and shortness of breath) [11]. Airway problems may be worsened by excessive thick secretions due to chronic or recurrent ear and sinus infections. Progressive obstruction can result in sleep apnea with severe hypoxemia and right heart failure [1,2,12,13]. (See "Mechanisms and predisposing factors for sleep related breathing disorders in children" and "Evaluation of suspected obstructive sleep apnea in children".)

                                         

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