ABSTRACT
Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disease caused by deficiency of the lysosomal enzyme alpha-L-iduronidase. This enzyme is involved in the degradation of the glycosaminoglycans (GAGs) dermatan and heparan sulphate and its deficiency results in the accumulation of GAGs and a progressive multisystem disease. Cardiac involvement is common in MPS patients and usually consists of progressive valvular thickening with incompetence and cardiomyopathy. We present an attenuated MPS I patient with a primary apical left ventricular aneurysm not associated with ischemia. We speculate that the defect in GAG catabolism leads not only to the storage of GAGs but also to alterations of the myocardial extracellular matrix. The latter ultimately being responsible for the formation of the aneurysm. This case emphasizes the importance of careful surveillance for cardiac lesions in MPS patients.