The parents of a 2-year-old girl, recent immigrants from Guatemala, bring their child to you for the first time. The child was born at term after an uncomplicated pregnancy and deliv¬ery, and her neonatal course was uneventful. She sat without support at 6 months of age, pulled to a stand at 10 months, and began walking at 14 months. She has a 10-word vocabulary, and she can drink from a cup and feed herself with a spoon. You also learn that a previous child in the family died at the age of 5 years from “heart trouble.” On physical examination, you note contractures of the lower extremities, stiffness of the hands, somewhat coarse facial features, and an enlarged liver and spleen. The child’s growth is within normal limits, and her ex¬amination is otherwise normal. What is the most appropriate next step to diagnose this child’s condition?
A. Abdominal computerized tomography
B. A brain MRI (magnetic resonance imaging)
C. Tests for a storage disorder
D. Chromosomes
E. Thyroid function studies