Answer to CM-01: ( c)
The deficit of debranching enzyme produces the Glycogen Storage Disease Type III, AKA Cori Disease. It is an autosomal recessive disorder characterized by abnormal molecules of glycogen with short branches. The lack of activity of this enzyme in the liver results in hypoglycemia, since the patient can not use the hepatic glycogen to release glucose to blood during the intermeal periods. The lack of the enzyme in the muscles contributes to the patient weakness and fatigue. Accumulation of glycogen in hepatocytes and muscle, including the cardiac muscle, damage the structures and interfere with their function (Note the increased activity of specific enzymes, hepatomegaly and ventricular hypertrophy in this patient). The diagnosis is confirmed when a deficit of debranching enzyme is found in liver or muscle tissue. Fibroblasts and lymphocytes may also show the deficiency.
Deficit of (a), (b) and (e) would not produce an accumulation of glycogen since these enzymes participates in the synthesis. (d) is not related to metabolism of Glycogen, but with metabolism of bilirrubin. If there was a Deficit of (f) glucose 6 phosphatase (Glycogen Storage Disease Type I) the response to glucagon would be very impaired and the hypoglycemia would be very sever, since the conversion of glucose 6 phosphate to glucose catalyzed by this enzyme, is key not only in the use of liver glycogen, but also in gluconeogenesis, so the patient would depend only in the diet glucose for his metabolic requirements.
A very good review about Glycogen Storage Diseases can be found at:
Tegay, D: Glycogen-Storage Disease Type III
…and this is an interesting video that I found in youtube about the Histopathology of Heart and Liver in Glycogen storage Disease:
For those visitors interested in Histology and Histopathology, I suggest to review the videos of WashingtonDeceit’s channel in youtube:
They are great!