Cardiovascular System

Clinical complications related to heart disease occur in all individuals with MPS I, particularly during the later stages of MPS I disease.^[2] Evidence of cardiovascular involvement by echocardiography can be demonstrated much earlier than that derived from clinical observations.

Mildly affected people with the attenuated form of MPS I may develop problems with the aortic or mitral valves. Storage of GAGs within and around the valve leaflets results in their thickening and stiffening which can lead to progressive mitral and aortic regurgitation (Image 1).^[1] The 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 (Hurler-Scheie syndrome) can also develop valve disease and may need mitral or aortic valve replacement in their teens and twenties.^[2]

Image 1 - Pathological specimen showing thickened and deformed valvular leaves
Courtesy of J.E. Wraith, MD

In severe patients, as GAG storage continues in the heart, cardiomyopathy may trigger sudden death related to arrhythmia, coronary artery disease and cardiovascular collapse. A small subset of severe MPS I patients exhibit early onset of fatal endocardiofibroelastosis, presenting in the first year of life. Mitral regurgitation is the more common valvular disease in severe MPS I.^[1]

Valve replacement surgery may be considered early in association with a general assessment of a patient’s clinical condition. Cardiac evaluation through serial monitoring of ventricular size, wall thickness and function at regular intervals (at least annually) with echocardiography is useful in the treatment of patients. Bacterial endocarditis prophylaxis may be advised for MPS I patients with cardiac abnormalities.^[2]

Next: Ocular System

References:

1. Wippermann CF, Beck M, Schranz D, Huth R, Michel-Behnke I, Jungst BK. Mitral and aortic regurgitation in 84 patients with mucopolysaccharidoses. Eur J Pediatr 1995;154(2):98-101.

2. Neufeld, E.F., and Muenzer, J. (2001) The mucopolysaccharidoses. In: The Metabolic and Molecular Bases of Inherited Disease. Scriver, C.R., Beaudet, A.L., Sly, W.S., Valle, D., Childs, B., Kinzler, K.W., and Vogelstein, B. (eds.). 8th edition, Vol. III. McGraw- Hill, Medical Publishing Division, p. 3421.