The dermatan sulfate accumulates in MPS II: this results in substantial thickening, which results in either stenosis or regurgitation of the heart valve. We do see some cardiomyopathy, but it’s primarily valve disease that we’re concerned about in MPS II.

- Professor Joseph Muenzer


Cardiac symptoms in Hunter syndrome arise due to GAG depositions in various parts of the heart, which compromise the response to valve injury; 82% of Hunter syndrome patients suffer from cardiovascular involvement of some form, with valve disease and heart murmur being the most common symptoms, arising at an average age of 6 years old. 1,2 Other less frequent cardiac symptoms of Hunter syndrome include cardiomyopathy, tachycardia, hypertension, arrhythmia, and congestive heart failure. 1


Around 14% of deaths in Hunter syndrome are due to cardiac involvement, so the decision to perform surgical valve repair or replacement should not be unnecessarily delayed, despite an apparent absence of clinical cardiac effects, or the risks associated with general anaesthesia (intubation difficulties and post-procedural airway oedema). Cardiac monitoring and surgery are essential components of the multidisciplinary management of Hunter syndrome patients. 3,4

Regular echocardiography, 12-lead electrocardiography and Holter monitoring (if indicated) are used to monitor cardiac involvement in Hunter syndrome patients, typically every 1–3 years. 3,5 A chest X-ray can be used to monitor right or left ventricular hypertrophy, and a cardiac MRI or CT scan may also be useful to assess this symptom, or valve failure. 3 Before any surgeries are performed on Hunter syndrome patients though (cardiac or non-cardiac), a full cardiac assessment should be conducted. 3

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  1. Wraith JE et al. Initial report from the Hunter Outcome Survey. Genet Med 2008; 10(7): 508–516.
  2. Braunlin EA et al. Cardiac disease in patients with mucopolysaccharidosis: presentation, diagnosis and management. J Inherit Metab Dis 2011; 34(6): 1183–1197.
  3. Scarpa M et al. Mucopolysaccharidosis type II: European recommendations for the diagnosis and multidisciplinary management of a rare disease. Orphanet J Rare Dis 2011; 6: 72.
  4. Burton BK et al. Survival in idursulfase-treated and untreated patients with mucopolysaccharidosis type II: data from the Hunter Outcome Survey (HOS). J Inherit Metab Dis 2017; 40(6): 867–874.
  5. Muenzer J et al. Multidisciplinary management of Hunter syndrome. Pediatrics 2009; 124(6): e1228–e1239.