Information for Cardiologists

Because MPS I can affect many different organ systems, patients typically see several specialists before getting a diagnosis. Clinical complications related to heart disease occur in some patients with MPS I, particularly those with a more severe form of the disease. Heart disease may not develop or cause any problems until later in the patient’s life. Below are symptoms encountered by cardiologists that may lead to clinical suspicion of MPS I and warrant further testing.


In severe MPS I patients, as Glycosaminoglycan (GAG) storage continues in the heart, cardiomyopathy (weak heart muscle) may trigger sudden death related to arrhythmia, coronary artery disease and cardiovascular collapse. Hypertrophic cardiomyopathy may be diagnosed by echocardiography.

Endocardial Fibroelastosis

Although rare, patients with severe MPS I may present with fatal endocardial fibroelastosis, also known as stiff heart. This symptom can manifest early, between 6 to 12 months.

Mitral and aortic regurgitation

Patients with severe and attenuated form of MPS I may develop problems with the aortic or mitral valves. Storage of glycosaminoglycans (GAGs) within and around the valve leaflets results in their thickening and stiffening which can lead to progressive mitral and aortic regurgitation.[1] In patients on the attenuated end of the disease spectrum, valvular disease does not usually lead to hemodynamic effects until the later stages of disease. People with attenuated disease who have moderate-to-severe symptoms can also develop valve disease and may need mitral or aortic valve replacement in their teens and twenties.

Pathological specimen showing thickened and deformed valvular leaves. Credit: Courtesy of J.E. Wraith


Glycosaminoglycan (GAG) storage in the heart blood vessels can lead to stenosis and lead to death. Coronary artery disease caused by GAG storage is like that seen in older people.

Stenosis Credit: Illustration courtesy of the National MPS Society

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