The natural course and the impact of therapies of cardiac involvement in the mucopolysaccharidoses

Objective: To analyze cardiac involvement and its progression in mucopolysaccharidoses, and to assess the short term impact of new therapeutic strategies. Patients and methods: We studied echocardiographically 57 patients with various types of mucopolysaccharidoses, specifically types I, II, III, IV and VI, with a median age at the diagnosis of cardiac involvement of 5 years, following them for a median of 4.6 years, with a range from 0.9 to 21.2 years. We used a scoring system, along with the so-called delta score, to quantify the severity of involvement at baseline and at last examination, and to chart their progression over time. Results: Cases with cardiac involvement increased from 59.6% to 87.3% at the last examination. The scores increased with age, and were significantly different according to the specific type of mucopolysaccharidosis. Involvement of the mitral valve was most common, often associated with an aortic valvar anomaly and/or left ventricular hypertrophy. Patients with the first and second types had more severe involvement than those with the third or fourth types. Patients undergoing transplantation of haematopoietic stem cells seem to stabilize after an initial worsening while, in contrast, we were unable to demonstrate an effect of enzyme replacement therapy on the progression of the cardiac disease, possibly because those receiving such treatment had a higher median age, more severe cardiac disease and shorter follow-up. Conclusions: Cardiac involvement was present early in more than a half of the patients identified as having mucopolysaccharidosis, and generally progressed, being more frequent and severe in the first and second types of the disease. Longer follow-up is needed to demonstrate any significant improvement induced by new therapies.