MS-1902

A mother brings in her 8-month old child worried about her development. The baby has been having trouble with feeding and cannot sit without support. The mother is anxious because her first child was able to sit without support at 6 months. The child has a history of recurrent respiratory tract infections.

The doctor orders a series of blood tests to help identify potential causes.

After receiving the lab results, the doctor notes an abnormally high concentration of plasma lysosomal enzymes and positive inclusion bodies and peripheral blood lymphocytes.

What deficiency in enzymes is responsible for the symptoms seen in this child?