Glycogen storage diseases Practice Questions

Question 1

A 15-year-old boy is sent from gym class with a chief complaint of severe muscle aches. In class today he was competing with his friends and therefore engaged in weightlifting for the first time. A few hours later he was extremely sore and found that his urine was red when he went to urinate. This concerned him and he was sent to the emergency department for evaluation.

Upon further questioning, you learn that since childhood he has always had muscle cramps with exercise. Physical exam was unremarkable. Upon testing, his creatine kinase level was elevated and his urinalysis was negative for blood and positive for myoglobin.

Thinking back to biochemistry you suspect that he may be suffering from a hereditary glycogen disorder. Given this suspicion, what would you expect to find upon examination of his cells?

Accepted Answer

Normal glycogen structure

Answer

Short outer glycogen chains

Answer

Accumulation of glycogen in lysosomes forming dense granules

Answer

Glycogen without normal branching pattern

Answer

Absence of glycogen in muscles

Question 2

A 10-year-old boy is brought to the emergency department due to vomiting and weakness. He is attending a summer camp and was on a hike with the other kids and a camp counselor. His friends say that the boy skipped breakfast, and the counselor says he forgot to pack snacks for the kids during the hike. The child’s parents are contacted and report that the child has been completely healthy since birth. They also say there is an uncle who would have to eat regularly or he would have similar symptoms. At the hospital, his heart rate is 90/min, respiratory rate is 17/min, blood pressure is 110/65 mm Hg, and temperature is 37.0°C (98.6°F). Physical examination reveals a visibly lethargic child with slight disorientation to time and place. Mild hepatosplenomegaly is observed but no signs of dehydration are noted. A blood sample is drawn, and fluids are started via an intravenous line.
Lab report
Serum glucose 44 mg/dL
Serum ketones absent
    Serum creatinine 1.0 mg/dL
Blood urea nitrogen 32 mg/dL
    Alanine aminotransferase (ALT) 425 U/L
Aspartate aminotransferase (AST)  372 U/L
    Hemoglobin (Hb%) 12.5 g/dL
Mean corpuscular volume (MCV) 80 fl
Reticulocyte count 1%
Erythrocyte count 5.1 million/mm3
Which of the following is most likely deficient in this patient?

Accepted Answer

Acyl-CoA dehydrogenase

Answer

α-glucosidase

Answer

Glucose-6-phosphatase

Answer

Acetyl-CoA carboxylase

Answer

Nicotinic acid

Question 3

A 27-year-old Hispanic G2P1 presents for a routine antepartum visit at 26 weeks gestation. She has no complaints. The vital signs are normal, the physical examination is within normal limits, and the gynecologic examination corresponds to 25 weeks gestation. The oral glucose tolerance test (OGTT) with a 75-g glucose load is significant for a glucose level of 177 mg/dL at 1 hour and 167 mg/dL at 2 hour. The fasting blood glucose level is 138 mg/dL (7.7 mmol/L), and the HbA1c is 7%. Which of the following represents the proper initial management?

Accepted Answer

Insulin

Answer

Sitagliptin

Answer

Dietary and lifestyle modification

Answer

Metformin

Answer

Glyburide

Question 4

A 12-year-old girl comes to the clinic with a grossly enlarged abdomen. She has a history of frequent episodes of weakness, sweating, and pallor that are eliminated by eating. Her development has been slow. She started to walk unassisted at 2 years and was not performing well at school. Physical examination reveals a blood pressure of 100/60 mm Hg, heart rate of 80/min, and temperature of 36.9°C (98.4℉). On physical examination, the liver is enlarged, firm, and palpable up to the pelvis. The spleen and kidney are not palpable. Laboratory investigation reveals low blood glucose and pH with high lactate, triglycerides, ketones, and free fatty acids. The liver biopsy revealed high glycogen content. Hepatic glycogen structure was normal. The enzyme assay performed on the biopsy tissue revealed very low glucose-6-phosphatase levels. What is the most likely diagnosis?

Accepted Answer

Von-Gierke's disease

Answer

Pompe's disease

Answer

Cori's disease

Answer

Hereditary hemochromatosis

Answer

McArdle disease

Question 5

A 49-year-old woman presents to the family medicine clinic with concerns about her weight. She has been constantly gaining weight for a decade now as she has not been able to control her diet. She has tried exercising but says that she is too lazy for this method of weight loss to work. Her temperature is 37° C (98.6° F), respirations are 15/min, pulse is 67/min, and blood pressure is 122/88 mm Hg. Her BMI is 30. Her labs from her past visit show:
Fasting blood glucose: 149 mg/dL
Glycated hemoglobin (HbA1c): 9.1%
Triglycerides: 175 mg/dL
LDL-Cholesterol: 102 mg/dL
HDL-Cholesterol: 35 mg/dL
Total Cholesterol: 180 mg/dL
Serum creatinine: 1.0 mg/dL
BUN: 12 mg/dL
Serum:  
  Albumin: 4.2 gm/dL
  Alkaline phosphatase: 150 U/L
  Alanine aminotransferase:      76 U/L
  Aspartate aminotransferase: 88 U/L
After discussing the long term issues that will arise if her health does not improve, she agrees to modify her lifestyle and diet. Which of the following would be the best pharmacotherapy for this patient?

Accepted Answer

Metformin

Answer

Insulin

Answer

Dietary modification alone

Answer

Sitagliptin

Answer

Glipizide

Question 6

A 15-year-old boy comes to the physician because of severe muscle cramps and pain for 3 months. He first noticed these symptoms while attending tryouts for the high school football team. Since then, he becomes easily fatigued and has severe muscle pain and swelling after 10 minutes of playing. However, after a brief period of rest, the symptoms improve, and he is able to return to the game. Two days ago, he had an episode of reddish-brown urine after playing football. There is no family history of serious illness. He appears healthy. Vital signs are within normal limits. Physical and neurological examinations show no abnormalities. Serum creatine kinase concentration is 333 U/L. Urinalysis shows:
Blood 2+
Protein negative
Glucose negative
RBC negative
WBC 1–2/hpf
Which of the following is the most likely cause of this patient's symptoms?

Accepted Answer

Myophosphorylase deficiency

Answer

CTG repeat in the DMPK gene

Answer

Dystrophin gene mutation

Answer

Thyroid hormone deficiency

Answer

Acid maltase deficiency

Question 7

A newborn infant presents with severe weakness. He was born to a G1P1 mother at 40 weeks gestation with the pregnancy attended by a midwife. The mother's past medical history is unremarkable. She took a prenatal vitamin and folic acid throughout the pregnancy. Since birth, the child has had trouble breastfeeding despite proper counseling. He also has had poor muscle tone and a weak cry. His temperature is 99.5°F (37.5°C), blood pressure is 57/38 mmHg, pulse is 150/min, respirations are 37/min, and oxygen saturation is 96% on room air. Physical exam reveals poor muscle tone. The patient's sucking reflex is weak, and an enlarged tongue is noted. An ultrasound is performed, and is notable for hypertrophy of the myocardium. Which of the following is the most likely diagnosis?

Accepted Answer

Acid maltase deficiency

Answer

Familial hypertrophic cardiomyopathy

Answer

Clostridium tetani infection

Answer

Spinal muscular atrophy type I disease

Answer

Clostridium botulinum infection

Question 8

A 16-year-old boy comes to the physician because of muscle weakness and cramps for 5 months. He becomes easily fatigued and has severe muscle pain and swelling after 15 minutes of playing basketball with his friends. The symptoms improve after a brief period of rest. After playing, he sometimes also has episodes of reddish-brown urine. There is no family history of serious illness. Serum creatine kinase concentration is 950 U/L. Urinalysis shows:
Blood 2+
Protein negative
Glucose negative
RBC negative
WBC 1–2/hpf
Which of the following is the most likely underlying cause of this patient's symptoms?

Accepted Answer

Myophosphorylase deficiency

Answer

Medium-chain acyl-CoA dehydrogenase deficiency

Answer

Low levels of triiodothyronine and thyroxine

Answer

Acid maltase deficiency

Answer

CTG repeat in the DMPK gene

Question 9

A patient presents to the emergency room in an obtunded state. The patient is a known nurse within the hospital system and has no history of any medical problems. A finger stick blood glucose is drawn showing a blood glucose of 25 mg/dL.

The patient's daughter immediately arrives at the hospital stating that her mother has been depressed recently and that she found empty syringes in the bathroom at the mother's home. Which of the following is the test that will likely reveal the diagnosis?

Accepted Answer

C-peptide level

Answer

Fasting blood glucose

Answer

Urine metanephrines

Answer

Genetic testing

Answer

24 hr cortisol

Question 10

A 28-year-old man is brought in by ambulance to the ER, barely conscious, after feeling drowsy and falling to the floor during a presentation several hours ago. His colleague who accompanied him says he has had similar episodes 5 times in the past 3 months. No significant past medical history. His blood pressure is 110/80 mm Hg and pulse is 114/min. His capillary blood glucose is 15 mg/dL. Immediate IV dextrose with thiamine is started, and he rapidly regains consciousness. A contrast CT of the abdomen is performed which reveals a tumor in the pancreas. Which of the following relative laboratory findings would you most likely expect to find in this patient?

Accepted Answer

Glucose: ↓, Insulin: ↑, C-Peptide: ↑, Ketoacidosis: Absent

Answer

Glucose: ↑, Insulin: ↓, C-Peptide: ↓, Ketoacidosis: Present

Answer

Glucose: Normal, Insulin: Normal, C-Peptide: Normal, Ketoacidosis: Absent

Answer

Glucose: ↓, Insulin: ↑, C-Peptide: ↓, Ketoacidosis: Absent

Answer

Glucose: ↑, Insulin: ↑/Normal, C-Peptide: ↑/Normal, Ketoacidosis: Absent

Glycogen storage diseases

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Glycogen structure and metabolism overview

GSD type I (von Gierke disease)

GSD type II (Pompe disease)

GSD type III (Cori disease)

GSD type IV (Andersen disease)

GSD type V (McArdle disease)

GSD type VI (Hers disease)

GSD type VII (Tarui disease)

Clinical manifestations by tissue involvement

Diagnostic approaches to GSDs

Management strategies for GSDs

Genetics and inheritance of GSDs

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About Glycogen storage diseases for USMLE

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