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Micro & Immunology · patient case with 3 questions

Patient with a history of hepatitis C

Patient: 48-year-old man.

Chief complaint: Worn-down back teeth and jaw soreness in the mornings.

History: Hepatitis C diagnosed eight years ago, currently under hepatology follow-up. Reports morning jaw fatigue and has been told he grinds his teeth.

Findings: Generalized attrition with flattened cusps. Hypertrophy of the masticatory musculature bilaterally. No mucosal lesions.

Question 1

What type of genome does the hepatitis C virus carry?

  1. Single-stranded RNA
  2. Double-stranded RNA
  3. Single-stranded DNA
  4. Double-stranded DNA
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Correct answer: A. Single-stranded RNA

  • A. CORRECT. Hepatitis C is a Flaviviridae virus with a positive-sense SINGLE-STRANDED RNA genome. Its high mutation rate and multiple genotypes are why no vaccine exists, in contrast to hepatitis B.
  • B. Double-stranded RNA describes rotavirus.
  • C. Single-stranded DNA viruses include parvovirus B19.
  • D. Hepatitis B is the partially DOUBLE-STRANDED DNA hepatitis virus — a useful contrast point, since HBV is vaccine-preventable and HCV is not.

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Question 2

All of the following are true of hepatitis C EXCEPT:

  1. Infection is frequently asymptomatic for years
  2. It can progress to cirrhosis and hepatocellular carcinoma
  3. An effective vaccine is available
  4. It is a bloodborne pathogen
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Correct answer: C. An effective vaccine is available

  • A. Most acute infections are silent, which is why people can carry HCV for decades before it is detected. This is a true statement, not the exception.
  • B. Chronic infection leads to cirrhosis in a substantial proportion of patients, and cirrhosis carries a real annual risk of hepatocellular carcinoma.
  • C. CORRECT — this is the exception. There is NO vaccine for hepatitis C. The virus mutates rapidly and exists as multiple genotypes and quasispecies, which has defeated vaccine development. Hepatitis A and B are vaccine-preventable; C is not. It is, however, curable with direct-acting antivirals.
  • D. HCV is transmitted through blood — shared needles, transfusion before screening, and needlestick injury. This is why standard precautions apply to every patient.

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Question 3

Which muscle is most affected in bruxism?

  1. Masseter
  2. Buccinator
  3. Digastric
  4. Lateral pterygoid
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Correct answer: A. Masseter

  • A. CORRECT. The MASSETER is the most powerful elevator and takes the greatest load in clenching and grinding. Chronic parafunction produces masseteric hypertrophy, tenderness on palpation at the angle of the mandible, and the characteristic morning jaw fatigue this patient describes. The temporalis is the second most involved.
  • B. The buccinator is a muscle of facial expression that keeps the bolus between the teeth. It does not generate closing force.
  • C. The digastric is a depressor, active in opening rather than clenching.
  • D. The lateral pterygoid protrudes and depresses the mandible and is often tender in TMD, but it is not the principal force generator in bruxism.

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