A 4-year-old boy is brought to the pediatrician for a follow-up examination. He has course facial features, joint contractures, and hepatomegaly. Molecular analysis determines an inability to phosphorylate the sixth position on mannose. Which of the following is most likely to be seen in this patient?
Cherry red spot on the macula
Deficiency of myophosphorylase
Dilation of the rough endoplasmic reticulum (RER)
Increased serum enzyme levels
Misfolded protein retained in the RER
