Hunter Syndrome (Mucopolysaccharidosis Type II) Follow-up

Updated: Apr 18, 2018
  • Author: Germaine L Defendi, MD, MS, FAAP; Chief Editor: Maria Descartes, MD  more...
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Follow-up

Further Outpatient Care

The Hunter Outcome Survey (HOS), funded by Shire HGT (Shire Human Genetics Therapies, Inc.), was established to better understand the variability and progression of Hunter syndrome (MPS II) and to monitor the long-term treatment effects of Elaprase. This ongoing study encourages patient participation in order to gather data regarding clinical response to ERT. Both MPS II patients receiving treatment and those who are not are encouraged to participate. As of May 2007, 263 patients from 16 countries were enrolled; 24% were being treated with ERT. [12]

Annual follow-up includes the following:

  • Echocardiography and ECG
  • Pulmonary function tests
  • Liver and spleen volume (MRI)
  • Skeletal survey
  • 6-minute walk test (every 6 mo)
  • Quality of life and pain assessment
  • Urinary glycosaminoglycan (GAG) level and iduronate sulfatase (IDS) antibody measurement
  • Audiography
  • Baseline sleep study, repeated as needed
  • CBC count, comprehensive metabolic panel, and routine urinalysis
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Complications

Various complications may arise in the severe form of MPS II, including valvular heart disease and neurological complications. [42] Thickening of the tracheal walls may cause obstructive airway disease. Progression of abdominal organomegaly causes the abdominal wall to become markedly distended and hernias more prominent.

A study published in the Journal of Pediatrics evaluated the prevalence of cardiovascular manifestations in patients with Hunter syndrome. Using data from echocardiographic and electrocardiographic results from 102 patients who were enzyme replacement therapy–naïve in the Hunter Outcome Survey, the study found that, while valvular heart disease was the most common finding, left ventricular hypertrophy, elevated blood pressure, abnormal heart frequency, arrhythmia, and congestive heart failure were also noted. [43] The Hunter Outcome Survey (HOS) reports that 33% of patients develop hypertension.

Bone involvement occurs in MPS II, which may lead to short stature. All major joints, including the hips, knees, wrists, elbows, shoulders, and finger joints, become involved. This causes a decreased ability to pick up small objects, and, over time, walking becomes more difficult. The wrist is prone to carpal tunnel syndrome (CTS), which further decreases hand function.

A study published in the American Journal of Medical Genetics evaluated the prevalence, clinical manifestation, and nerve conduction profiles in 45 male patients with CTS and Hunter syndrome. A significant difference was noted in age between patients’ hands with normal, mild, moderate, and severe grades of CTS. It was also noted that the compound muscle action potential and sensory nerve action potential amplitudes of the median nerves decreased with age. These results suggest that Hunter syndrome may contribute to CTS in children. [44]

The Hunter Outcome Survey (HOS) reports that 84% of patients have neurological involvement (primarily behavioral and cognitive abnormalities). [12] Using data from neurobehavioral standardized assessments of patients with MPS II evaluated at the Program for Neurodevelopmental Function in Rare Disorders, one study sought to identify early clinical markers of neurologic involvement in MPS II. The study results noted that subsequent cognitive dysfunction was strongly associated with sleep disturbance, hyperactivity, behavior difficulties, seizurelike behavior, perseverative chewing behavior, and an inability to achieve bowel and bladder training; a new severity score was also developed, with a score greater than or equal to 3 indicating a high likelihood of developing CNS disease. [45]

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Prognosis

The life expectancy in patients with the severe form (MPS IIA) is only about 10-15 years; however, those with the milder form (MPS IIB) may live well into the seventh or eighth decades of life with supportive care and management.

Following hematopoietic stem cell transplant (HSCT), the characteristic cutaneous papules tend to regress, and most are gone 3 months posttransplant.

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Patient Education

Support groups serve as excellent resources for families and caregivers. Some of these support organizations include the following:

National Organization for Rare Disorders, Inc (NORD)

55 Kenosia Ave

PO Box 1968

Danbury, CT 06813-1968

Phone: (203) 744-0100

Toll-free: (800) 999-6673

Fax: (203) 798-2291

The Society for Mucopolysaccharide Diseases

46 Woodside Road

Amersham

Buckinghamshire, HP6 6AJ

United Kingdom

Phone: 0845 389 9901

Fax: 0845 389 9902

National MPS Society

PO Box 14686

Durham, NC 27709-4686

Phone; (919) 806-0101 or (877) MPS-1001

Email: info@mpssociety.org

Children Living with Inherited Metabolic Diseases (CLIMB)

The Quadrangle, Crewe Hall

Weston Road

Crewe

Cheshire, CW1-6UR

England, United Kingdom

(127) 0 2 50221

Mucopolysaccharide & Related Diseases Society Australia Ltd. 

PO Box 623

Hornsby, NSW 2077

Australia

Phone: 612.9476.8411

Fax: 612.9476.8422

Email: info@mpssociety.org.au

The Canadian Society for Mucopolysaccharide and Related Diseases Inc.

PO Box 30034 RPO Parkgate

North Vancouver BC, V7H 2YB

Phone: (604) 924-5130

Toll-free: (800) 667-1846

Fax: (604) 924-5131

Email: kirsten@mpssociety.ca

Other sources of information include the following:

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