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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