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Mucopolysaccharidosis I presenting with endocardial fibroelastosis of infancy
M J Stephan1, E L Stevens, R J Wenstrup
1Department of Pediatrics, Madigan Army Medical Center, Tacoma, Wash 98431.
Insights
Hurler syndrome (mucopolysaccharidosis I) can cause fatal cardiac failure due to endocardial fibroelastosis in infants. Early consideration of this rare genetic disorder is crucial for infants with cardiac abnormalities.
Area of Science:
- Pediatric Cardiology
- Medical Genetics
- Biochemistry
Background:
- Hurler syndrome, a type of mucopolysaccharidosis I (MPS I), is a rare genetic disorder.
- It results from alpha-L-iduronidase deficiency, leading to mucopolysaccharide accumulation.
- Cardiac complications, including endocardial fibroelastosis, are known but not always the primary presenting feature.
Observation:
- Two female infants with Hurler syndrome presented with fatal cardiac failure.
- Autopsy revealed endocardial fibroelastosis in both infants.
- Characteristic clear cells were identified within the myocardium and endocardium.
Findings:
- Alpha-L-iduronidase deficiency was confirmed in one infant.
- Histologic evidence of mucopolysaccharide accumulation and a sibling with Hurler syndrome were noted in the other.
- Mucopolysaccharide accumulation in the myocardium and endocardium is proposed to induce endocardial proliferation.
Implications:
- Cardiac failure may precede other recognized clinical or radiographic signs of Hurler syndrome.
- Mucopolysaccharidosis I should be considered in infants with endocardial fibroelastosis.
- This highlights the importance of considering heritable storage disorders in pediatric cardiac cases.
Abstract:
We describe two female infants with Hurler syndrome (mucopolysaccharidosis I) whose deaths are attributed to cardiac failure with associated, autopsy-confirmed endocardial fibroelastosis. One infant had confirmed alpha-L-iduronidase deficiency in cultured dermal fibroblasts, and the other infant had histologic evidence of tissue mucopolysaccharide accumulation at autopsy and a sibling with confirmed alpha-L-iduronidase deficiency and the Hurler syndrome phenotype. Clear cells ("Hurler" cells) were identified within the myocardium and endocardium of both infants. We propose that the ventricular mural accumulation of mucopolysaccharides induced extensive proliferation of elastic or collagen fibers within the endocardium. Cardiac failure may precede recognition of clinical and roentgenographic features of Hurler syndrome. Our findings and a literature review suggest that certain heritable storage disorders, including mucopolysaccharidosis I, should be considered when infants have clinical electrocardiographic and echocardiographic findings consistent with endocardial fibroelastosis or have autopsy-documented endocardial fibroelastosis.