10 USMLE Pathology, Hematology and Genetics Quick Review Questions with Answers (Set 4)

These 10 quick USMLE review questions test high-yield facts that show up again and again on the exam: Lesch-Nyhan syndrome, pemphigus, inheritance patterns, type IV hypersensitivity, osteogenesis imperfecta, liquefactive necrosis, xeroderma pigmentosum, apoptosis, food allergy and giant cells. Each question includes the correct answer.

Written by Dr. Ray Makar, MD, author of the Repeated USMLE Questions eBook series.

Prefer video? Watch daily USMLE case questions on MedFocus by Dr. Ray on YouTube.

How to use this page: read the question, pick your answer, then tap Show Answer and Explanation.

Questions

Question 1. Which one of the following enzymes is associated with Lesch-Nyhan syndrome?

A- Adenosine deaminase
B- Hypoxanthine-guanine phosphoribosyl transferase
C- Ribonucleotide reductase
D- Xanthine oxidase

B- Hypoxanthine-guanine phosphoribosyl transferase- This enzyme is a part of the salvage pathway for purines. A deficiency leads to inability to recycle purines which results in overproduction of uric acid. Individuals with Lesch-Nyhan syndrome are mentally retarded.
The correct answer is B

 

Question 2. Pemphigus is an autoimmune skin disease associated with which of the following structures? ,?

A- Cell matrix junctions
B- Desmosomes
C- Gap junctions
D- Tight junctions

B- Desmosomes- Pemphigus is caused by autoantibodies against the transmembrane glycoproteins. These antibodies bind to proteins and disrupt the desmosomes.
The correct answer is B

 

Question 3. What is the correct match regarding the genetic transmission of the following diseases?

A- Duchenne muscular dystrophy- X-linked dominant
B- Huntington’s disease- Autosomal recessive
C- Hypophosphatemic rickets- X-linked recessive
D- Leber hereditary optic neuropathy- Mitochondrial inheritance

D- Leber hereditary optic neuropathy- Mitochondrial inheritance- Duchenne muscular dystrophy- X-linked recessive- Hypophosphatemic rickets- X-linked dominant- Huntington’s disease- Autosomal dominant-
The correct answer is D

 

Question 4. Which type of hypersensitivity reaction develops from Mycobacterium tuberculosis?

A- Type I
B- Type II
C- Type III
D- Type IV

D- Type IV- A- Anaphylaxis. B- Transfusion reactions, hemolytic anemia and Goodpasture syndrome. C- Serum sickness, Arthus reaction, rheumatoid arthritis and lupus nephritis.
The correct answer is D

 

Question 5. Which one of the following disorders is accompanied by blue sclera?

A- Duchenne muscular dystrophy
B- Neurofibromatosis type 2
C- Osteogenesis imperfecta
D- Systemic lupus erythematosus

C- Osteogenesis imperfecta- it is type 1 collagen defect affects bones and sclera.
The correct answer is C

 

Question 6. Which of the following types of necrosis occurs in abscesses and brain infarcts?

A- Caseous necrosis
B- Coagulative necrosis
C- Fibrinoid necrosis
D- Liquefaction necrosis

D- Liquefaction necrosis- This type occurs also in pancreatic necrosis as well as abscesses and brain infarcts. A- Occurs in TB. B- Occurs in heart, liver and kidney infarction and C- Occurs in acute immunological injuries.
The correct answer is D

 

Question 7. A young boy presents with multiple skin lesions for more than a year. He is sensitive to sun and biopsies of some of his lesions show squamous cell carcinoma. Which of the following mutations is most likely present in this condition?

A- Missense mutation
B- Nonsense mutation
C- Point mutation
D- Thymidine dimers

D- Thymidine dimers- This is most likely a case of xeroderma pigmentosa. It is an autosomal recessive disease characterized by defect in excision repair. Ultraviolet light exposure leads to the formation of thymidine dimers which are not repaired due to this mutation.
The correct answer is D

 

Question 8. Loss of individual cells by fragmentation of nuclei and cytoplasm caused by a chemotherapeutic agent is produced through which one of the following mechanisms?

A- Acute inflammation
B- Apoptosis
C- Mitochondrial poisoning
D- Phagocytosis

B- Apoptosis- This is a process of induction of death of neoplastic cells.
The correct answer is B

 

Question 9. Food allergies typically cause which one of the following immunologic abnormalities?

A- Cell-mediated hypersensitivity
B- Complement activation
C- Immune-complex deposition
D- Localized anaphylaxis

D- Localized anaphylaxis- Food allergy is a form of type 1 hypersensitivity which is characterized by local reaction on the skin and/or gastrointestinal tract. It is caused by a reaction of allergen with IgE bound to mast cells.
The correct answer is D

 

Question 10. Which one of the following types of cells is involved in foreign body reaction?

A- Eosinophil
B- Giant cell
C- Neutrophil
D- Plasma cell

B- Giant cell
The correct answer is B

 

High-yield points from this set

  • Pemphigus vulgaris = antibodies against desmosomes.
  • Leber hereditary optic neuropathy is mitochondrially inherited.
  • Liquefactive necrosis occurs in abscesses and brain infarcts.
  • Xeroderma pigmentosum = failure to repair thymidine dimers.

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