MFDS Human Disease 2 — Questions and Answers
Question 1: Which cardiac condition most significantly increases the risk of prolonged QT syndrome with erythromycin?
- Mitral valve prolapse
- Pre-existing QT prolongation or concurrent QT-prolonging drugs (Correct answer)
- Atrial fibrillation
- Left bundle branch block
Correct answer: Pre-existing QT prolongation or concurrent QT-prolonging drugs
Erythromycin prolongs the cardiac QT interval by blocking hERG potassium channels; this risk is greatly amplified in patients with a pre-existing long QT interval or on other QT-prolonging drugs.
Question 2: Behçet's disease is characterised by the triad of:
- Oral ulcers, genital ulcers and uveitis (Correct answer)
- Oral ulcers, arthritis and psoriasis
- Xerostomia, arthritis and keratoconjunctivitis
- Oral ulcers, skin lesions and hepatitis
Correct answer: Oral ulcers, genital ulcers and uveitis
Behçet's disease is a systemic vasculitis characterised by the classic triad of recurrent oral ulcers, genital ulcers and uveitis (International Study Group criteria).
Question 3: Which liver disease most significantly impairs drug metabolism in dental practice?
- Hepatitis A (acute)
- Severe cirrhosis (Correct answer)
- Non-alcoholic fatty liver disease
- Primary biliary cholangitis (early stage)
Correct answer: Severe cirrhosis
Severe cirrhosis markedly reduces hepatic drug-metabolising capacity (cytochrome P450 activity) and can impair clotting factor synthesis, both clinically relevant in dental prescribing.
Question 4: A patient with chronic renal failure presents for extraction. The main concern regarding drug prescribing is:
- Increased hepatic clearance of drugs
- Accumulation of renally excreted drugs and metabolites (Correct answer)
- Resistance to local anaesthetics
- Reduced need for antibiotics
Correct answer: Accumulation of renally excreted drugs and metabolites
In chronic renal failure, renally excreted drugs (e.g. some penicillins, NSAIDs) accumulate to toxic levels, requiring dose reduction or alternative agents.
Question 5: Which immune deficiency syndrome most significantly predisposes to invasive oral candidiasis?
- IgA deficiency
- Common variable immunodeficiency
- HIV/AIDS (CD4 <200) (Correct answer)
- Chronic granulomatous disease
Correct answer: HIV/AIDS (CD4 <200)
Severe CD4 lymphocytopenia in HIV/AIDS (particularly CD4 <200 cells/μL) profoundly impairs cell-mediated immunity, predisposing to invasive and oropharyngeal candidiasis.
Question 6: Which feature distinguishes Crohn's disease from ulcerative colitis in oral manifestations?
- Aphthous ulcers are exclusive to UC
- Cobblestone buccal mucosa and lip swelling occur in Crohn's (Correct answer)
- Pyostomatitis vegetans is only in Crohn's
- Geographic tongue is specific to UC
Correct answer: Cobblestone buccal mucosa and lip swelling occur in Crohn's
Oral Crohn's disease produces characteristic cobblestone (polypoid) buccal mucosa, lip swelling (orofacial granulomatosis) and linear ulcers not seen in UC.
MFDS Human Disease 2
Which cardiac condition most significantly increases the risk of prolonged QT syndrome with erythromycin?