1. A 24-year-old woman presents with rectal bleeding, urgency, and tenesmus. Flexible sigmoidoscopy shows inflammation limited to the rectum (proctitis), extending about 10 cm from the anal verge. She has no prior inflammatory bowel disease treatment. Which initial regimen delivers the highest mucosal drug concentration to the affected segment with the least systemic exposure?
A) Oral mesalamine multi-matrix (MMX) tablet alone
B) A mesalamine suppository
C) Oral prednisone 40 mg daily
D) Intravenous methylprednisolone
E) Oral sulfasalazine alone
ANSWER: B
Rationale:
For proctitis confined to the distal 10 to 15 cm, a mesalamine suppository delivers a high concentration of active 5-aminosalicylic acid directly to the rectal mucosa with minimal systemic absorption, making it the most appropriate and best-tolerated first-line therapy. Topical rectal 5-aminosalicylic acid is superior to oral therapy alone for distal disease because it achieves far higher local mucosal levels.
Option A: Option A is incorrect: an oral MMX tablet releases drug throughout the colon and achieves comparatively low concentrations in the rectum, so it is less effective than a suppository for isolated proctitis.
Option C: Option C is incorrect: systemic prednisone exposes the patient to corticosteroid toxicity and has no maintenance role; it is not appropriate first-line therapy for mild proctitis that responds to topical 5-aminosalicylic acid.
Option D: Option D is incorrect: intravenous methylprednisolone is reserved for severe acute colitis, not limited proctitis, and carries substantial systemic risk.
Option E: Option E is incorrect: oral sulfasalazine delivers drug less effectively to the distal rectum than a topical agent and adds sulfapyridine-related toxicity.
2. A 29-year-old man with ulcerative colitis maintained on sulfasalazine reports nausea, headaches, and—after attempting conception with his partner—a semen analysis showing low sperm count. He is otherwise well. What is the most appropriate explanation and management step?
A) These effects are caused by the 5-aminosalicylic acid moiety and will persist regardless of formulation
B) The low sperm count is irreversible and unrelated to his medication
C) He should stop all 5-aminosalicylic acid therapy permanently because the effects indicate a hypersensitivity reaction
D) These effects are attributable to the sulfapyridine carrier, the oligospermia is reversible on discontinuation, and switching to a sulfapyridine-free mesalamine formulation is appropriate
E) He should continue sulfasalazine unchanged because these symptoms are unrelated to the drug
ANSWER: D
Rationale:
Nausea, headache, and reversible oligospermia are classic sulfapyridine-related adverse effects of sulfasalazine; the therapeutic activity resides in the 5-aminosalicylic acid moiety, while the sulfapyridine carrier accounts for most of the toxicity. The oligospermia reverses after discontinuation, and switching to a sulfapyridine-free mesalamine formulation preserves anti-inflammatory therapy while removing the offending carrier—an appropriate step for a man attempting conception.
Option A: Option A is incorrect: these effects derive from the sulfapyridine carrier, not the 5-aminosalicylic acid moiety, and they resolve when a sulfa-free formulation is used.
Option B: Option B is incorrect: sulfasalazine-associated oligospermia is characteristically reversible and is drug-related.
Option C: Option C is incorrect: these are dose-related carrier effects, not a hypersensitivity reaction, and sulfa-free mesalamine remains an appropriate option.
Option E: Option E is incorrect: the symptoms are drug-related, so continuing sulfasalazine unchanged ignores a remediable cause of his infertility concern.
3. A 35-year-old man of Mediterranean descent with newly diagnosed ulcerative colitis is started on sulfasalazine. Ten days later he presents with fatigue, jaundice, dark urine, and a hemoglobin drop; peripheral smear shows bite cells and the reticulocyte count is elevated. Which underlying condition best explains this reaction, and what is the correct response?
A) Glucose-6-phosphate dehydrogenase (G6PD) deficiency, in which the oxidant sulfapyridine carrier precipitates acute hemolytic anemia; stop sulfasalazine and switch to a sulfapyridine-free mesalamine formulation
B) Thiopurine S-methyltransferase deficiency, requiring a thiopurine dose reduction
C) An anti-drug antibody response to the biologic component of sulfasalazine
D) Folate deficiency causing megaloblastic anemia, treated by increasing the dose
E) Methemoglobinemia from the 5-aminosalicylic acid moiety, treated by continuing the drug
ANSWER: A
Rationale:
The clinical picture—jaundice, dark urine, falling hemoglobin, bite cells, and reticulocytosis—is acute hemolytic anemia. In a patient of Mediterranean descent this strongly suggests glucose-6-phosphate dehydrogenase (G6PD) deficiency, in which red cells cannot defend against oxidative stress. Sulfasalazine's sulfapyridine carrier is an oxidant sulfonamide that can precipitate hemolysis in such patients. The correct response is to stop sulfasalazine and switch to a sulfapyridine-free mesalamine formulation, which lacks the offending oxidant.
Option B: Option B is incorrect: thiopurine S-methyltransferase deficiency relates to thiopurine myelosuppression, not sulfasalazine-induced hemolysis.
Option C: Option C is incorrect: sulfasalazine is not a biologic and the reaction is oxidative hemolysis, not an anti-drug antibody response.
Option D: Option D is incorrect: the smear and reticulocytosis indicate hemolysis, not megaloblastic anemia, and increasing the dose would worsen the reaction.
Option E: Option E is incorrect: the hemolysis arises from the sulfapyridine carrier, not the 5-aminosalicylic acid moiety, and continuing the drug would be dangerous.
4. A 41-year-old woman with ileocecal Crohn's disease has been well controlled on oral budesonide controlled-ileal-release with no Cushingoid features. Three weeks after starting itraconazole (an azole antifungal that potently inhibits the liver enzyme CYP3A4) for onychomycosis, she develops moon facies, acne, and new glucose intolerance. What is the most likely explanation?
A) Budesonide has lost efficacy because the antifungal accelerated its clearance
B) The antifungal directly caused Cushing syndrome independent of budesonide
C) The new findings are unrelated to either drug and reflect undiagnosed primary adrenal disease
E) Itraconazole inhibited CYP3A4-mediated first-pass metabolism of budesonide, raising its systemic exposure and producing systemic corticosteroid effects
ANSWER: E
Rationale:
Budesonide's low systemic exposure depends on extensive first-pass metabolism by CYP3A4. Itraconazole is a potent CYP3A4 inhibitor; by blocking that first-pass clearance, it allows more intact budesonide to reach the systemic circulation, producing systemic corticosteroid effects such as moon facies, acne, and glucose intolerance. Recognizing this interaction—and reducing or stopping budesonide or choosing a non-interacting antifungal—is the appropriate response.
Option A: Option A is incorrect: CYP3A4 inhibition reduces clearance and raises exposure, so efficacy is not lost through accelerated clearance.
Option B: Option B is incorrect: the Cushingoid features result from elevated budesonide levels, not a direct steroidogenic effect of the antifungal.
Option C: Option C is incorrect: the temporal link to itraconazole and the known interaction make primary adrenal disease an unnecessary explanation.
Option D: Option D is incorrect: systemic budesonide exposure rose, not fell; a fall would not produce steroid excess.
5. A 33-year-old man is hospitalized with severe acute ulcerative colitis: 10 bloody stools daily, tachycardia, fever, and elevated inflammatory markers. He is started on intravenous methylprednisolone 60 mg daily. On day 3, validated indices show no meaningful improvement and he continues to have frequent bloody stools. What is the most appropriate next step?
A) Continue intravenous methylprednisolone unchanged for another 10 days before reassessing
B) Switch to oral budesonide and plan discharge
C) Initiate rescue therapy with infliximab or intravenous cyclosporine
D) Start azathioprine monotherapy to induce remission over the next few days
E) Add adrenocorticotropic hormone (ACTH) to augment endogenous cortisol production
ANSWER: C
Rationale:
In severe acute ulcerative colitis, response to intravenous corticosteroids is assessed formally at day 3. A patient without meaningful response should move to rescue therapy—infliximab or intravenous cyclosporine—rather than continuing ineffective steroids beyond roughly 5 to 7 days, because delay increases the risk of complications and colectomy.
Option A: Option A is incorrect: prolonging unchanged intravenous steroids in a day-3 non-responder is precisely what should be avoided.
Option B: Option B is incorrect: oral budesonide is a topically acting agent for mild to moderate disease and is wholly inadequate for steroid-refractory severe colitis; discharge would be unsafe.
Option D: Option D is incorrect: thiopurines take months to act and cannot induce remission in an acute severe flare.
Option E: Option E is incorrect: ACTH has been abandoned in favor of direct corticosteroids and is not appropriate rescue therapy.
6. A 47-year-old woman with Crohn's disease is started on standard-dose azathioprine without prior pharmacogenomic testing. Three weeks later she presents with fever, mouth ulcers, and profound pancytopenia (white cells, hemoglobin, and platelets all severely depressed). Which mechanism best explains this catastrophic reaction, and what is the immediate action?
A) She is almost certainly a thiopurine S-methyltransferase (TPMT) poor metabolizer, so loss of the methylation pathway drove 6-mercaptopurine into producing very high active 6-thioguanine nucleotide levels and severe myelosuppression; stop the thiopurine immediately and provide supportive care
B) She has developed a 5-aminosalicylic acid hypersensitivity reaction; switch to sulfasalazine
C) The pancytopenia reflects xanthine oxidase overactivity generating excess thiouric acid; increase the azathioprine dose
D) This is expected dose-independent toxicity that occurs in all patients and requires no dose change
E) The reaction is methotrexate-induced mucositis; administer leucovorin
ANSWER: A
Rationale:
Profound early pancytopenia after starting standard-dose azathioprine without testing is the classic presentation of an undetected thiopurine S-methyltransferase (TPMT) poor metabolizer. With the methylation exit largely absent, 6-mercaptopurine is channeled into the anabolic HPRT pathway, producing very high active 6-thioguanine nucleotide concentrations and severe, potentially life-threatening myelosuppression. The immediate action is to stop the thiopurine and provide supportive care; this scenario is exactly why TPMT (and NUDT15) testing is performed before initiation.
Option B: Option B is incorrect: this is thiopurine-induced marrow suppression, not 5-aminosalicylic acid hypersensitivity, and sulfasalazine would not address it.
Option C: Option C is incorrect: xanthine oxidase produces inactive thiouric acid and does not cause this picture; increasing the dose would be lethal.
Option D: Option D is incorrect: the toxicity is dose- and genotype-dependent, not an unavoidable universal effect, and continuing dosing would be dangerous.
Option E: Option E is incorrect: the patient received azathioprine, not methotrexate, and leucovorin does not rescue thiopurine myelosuppression.
7. A 28-year-old man of Korean ancestry with Crohn's disease has a documented normal thiopurine S-methyltransferase (TPMT) genotype and is started on weight-based azathioprine. Within two weeks he develops severe leukopenia and early alopecia. TPMT testing is rechecked and confirmed normal. What is the most likely explanation?
A) A laboratory error in the TPMT assay, since myelosuppression cannot occur with normal TPMT
B) Non-adherence, since adherent patients with normal TPMT never develop cytopenias
C) Acute 5-aminosalicylic acid toxicity from a concurrent mesalamine product
D) A loss-of-function NUDT15 (nudix hydrolase 15) variant allowing thioguanine triphosphate metabolites to accumulate and cause myelosuppression independent of TPMT, a mechanism especially common in East Asian patients
E) Folate deficiency causing the leukopenia, correctable with folic acid alone
ANSWER: D
Rationale:
NUDT15 (nudix hydrolase 15) inactivates thiopurine triphosphate metabolites; a loss-of-function NUDT15 variant lets these metabolites accumulate and cause myelosuppression and alopecia even when TPMT activity is entirely normal. Such variants are substantially more common in East Asian populations, fitting this patient of Korean ancestry. This is the prototypical case for which both TPMT and NUDT15 are tested before thiopurine therapy.
Option A: Option A is incorrect: a normal TPMT does not exclude myelosuppression precisely because NUDT15 acts independently, so it is not evidence of a lab error.
Option B: Option B is incorrect: NUDT15-mediated toxicity occurs in adherent patients with normal TPMT, so non-adherence is not required.
Option C: Option C is incorrect: the picture is thiopurine-induced myelosuppression, not 5-aminosalicylic acid toxicity.
Option E: Option E is incorrect: folate deficiency does not explain rapid severe leukopenia with alopecia after azathioprine, and folic acid alone would not address NUDT15-mediated toxicity.
8. A 39-year-old woman with Crohn's disease on azathioprine has persistent disease activity despite dose escalation. Metabolite testing shows markedly elevated 6-methylmercaptopurine with low active 6-thioguanine nucleotides, and her transaminases are twice the upper limit of normal. Which intervention best addresses both her therapeutic failure and her hepatotoxicity?
A) Double the azathioprine dose to overcome therapeutic failure
B) Add low-dose allopurinol (a xanthine oxidase inhibitor) while reducing the azathioprine dose to roughly 25 to 33 percent, shifting metabolism toward active 6-thioguanine nucleotides and away from the hepatotoxic methylated metabolite
C) Stop azathioprine and start full-dose allopurinol alone as monotherapy for Crohn's disease
D) Continue the current azathioprine dose unchanged and add a hepatoprotective supplement
E) Add full-dose allopurinol without changing the azathioprine dose
ANSWER: B
Rationale:
This metabolite pattern—high 6-methylmercaptopurine with low 6-thioguanine nucleotides—is preferential methylation, which causes both hepatotoxicity (from the methylated metabolite) and therapeutic failure (from inadequate active metabolite) despite escalating doses. Adding low-dose allopurinol inhibits xanthine oxidase and redirects metabolism toward the active 6-thioguanine nucleotide pathway, correcting the pattern; because this sharply increases active metabolite formation, the azathioprine dose must be reduced to roughly 25 to 33 percent with intensified monitoring.
Option A: Option A is incorrect: doubling the dose worsens 6-methylmercaptopurine-driven hepatotoxicity without correcting the underlying shunting.
Option C: Option C is incorrect: allopurinol is not a treatment for Crohn's disease and cannot serve as monotherapy.
Option D: Option D is incorrect: leaving the dose unchanged ignores the correctable metabolic problem and the ongoing hepatotoxicity.
Option E: Option E is incorrect: adding allopurinol without reducing the azathioprine dose risks fatal 6-thioguanine nucleotide accumulation and myelosuppression.
9. A 45-year-old man with moderate-to-severe Crohn's disease previously discontinued azathioprine because of intolerance. He is now starting infliximab. The team wants to reduce the chance of anti-drug antibody formation that could shorten the biologic's durability. Which strategy is best supported by the evidence, including the SONIC trial (which showed combination azathioprine plus infliximab superior to either agent alone in Crohn's disease)?
A) Use infliximab alone, because combining it with any immunomodulator offers no benefit
B) Restart full-dose azathioprine despite his documented intolerance
C) Use a corticosteroid as the long-term companion to the biologic to suppress antibody formation
D) Withhold the biologic until the patient has been in steroid-free remission for one year
E) Combine infliximab with low-dose methotrexate as the immunomodulator companion, since the principle from SONIC—an immunomodulator reduces anti-drug antibody formation and improves durability—applies, and methotrexate is the reasonable choice given his thiopurine intolerance
ANSWER: E
Rationale:
The principle established by SONIC (trial showing combination azathioprine plus infliximab superior to either agent alone in Crohn's disease) is that pairing an immunomodulator with an anti-tumor necrosis factor biologic reduces anti-drug antibody formation and improves durability of response. Because this patient cannot tolerate a thiopurine, low-dose methotrexate is the reasonable immunomodulator companion, transferring the SONIC principle to an agent he can take.
Option A: Option A is incorrect: combination therapy does provide benefit by lowering immunogenicity, so biologic monotherapy is not the best antibody-reduction strategy.
Option B: Option B is incorrect: restarting a drug he is documented to be intolerant of is inappropriate when an alternative immunomodulator exists.
Option C: Option C is incorrect: corticosteroids have no maintenance role and are not the immunomodulator companion that reduces biologic immunogenicity.
Option D: Option D is incorrect: withholding the biologic for a year contradicts the need to treat moderate-to-severe disease and offers no immunogenicity advantage.
10. A 31-year-old woman with Crohn's disease maintained on weekly methotrexate presents for a routine visit. She reports a missed period, and a urine pregnancy test in clinic is positive. She had not been using reliable contraception. What is the most appropriate immediate management?
A) Continue methotrexate at the current dose because the anti-inflammatory effect protects the pregnancy
B) Reduce the methotrexate dose by half and continue through the first trimester
C) Stop methotrexate immediately and arrange urgent obstetric evaluation, because methotrexate is teratogenic and abortifacient and is absolutely contraindicated in pregnancy
D) Continue methotrexate but add high-dose folic acid, which neutralizes its teratogenic risk
E) Switch methotrexate to sulfasalazine today and assume the pregnancy is unaffected
ANSWER: C
Rationale:
Methotrexate is teratogenic and abortifacient and is absolutely contraindicated in pregnancy; it inhibits trophoblast proliferation and fetal folate metabolism and has caused spontaneous abortion, fetal death, and major malformations at therapeutic doses. On discovering pregnancy, the correct action is to stop methotrexate immediately and arrange urgent obstetric evaluation.
Option A: Option A is incorrect: methotrexate does not protect the pregnancy—it endangers it—so continuing is dangerous.
Option B: Option B is incorrect: dose reduction does not make methotrexate safe in pregnancy; it must be stopped.
Option D: Option D is incorrect: folic acid mitigates certain maternal toxicities but does not neutralize methotrexate's teratogenicity, so continuing the drug is unacceptable.
Option E: Option E is incorrect: although switching off methotrexate is correct in principle, assuming the pregnancy is unaffected is inappropriate; urgent obstetric assessment is required given the exposure.
11. A 58-year-old man with Crohn's disease has taken weekly methotrexate for several years (estimated cumulative dose exceeding 1.5 g). He has type 2 diabetes and obesity. Routine monitoring shows alanine aminotransferase and aspartate aminotransferase persistently above twice the upper limit of normal on two consecutive checks. What is the most appropriate management?
A) Reduce the methotrexate dose and recheck liver enzymes; if elevations persist despite dose reduction, discontinue methotrexate and obtain hepatology evaluation, recognizing his cumulative dose and metabolic risk factors for hepatic fibrosis
B) Continue the current dose unchanged, since transaminase elevations on methotrexate are never clinically meaningful
C) Increase the methotrexate dose to improve disease control, accepting the transaminase rise
D) Stop monitoring liver enzymes, since fibrosis cannot be detected biochemically
E) Switch to high-dose methotrexate to overcome apparent resistance
ANSWER: A
Rationale:
Methotrexate causes dose-dependent hepatic fibrosis, and this patient carries multiple risk factors—cumulative dose exceeding 1.5 g, obesity, and type 2 diabetes. Persistent transaminase elevation above twice the upper limit of normal on consecutive measurements warrants dose reduction with rechecking; if elevations persist despite reduction, methotrexate should be discontinued and hepatology evaluation obtained, with non-invasive fibrosis assessment as appropriate.
Option B: Option B is incorrect: persistent elevations in a high-risk patient are clinically meaningful and require action.
Option C: Option C is incorrect: increasing the dose would worsen hepatotoxicity.
Option D: Option D is incorrect: liver enzyme monitoring remains a key surveillance tool and should not be stopped; non-invasive fibrosis markers supplement it rather than replace monitoring.
Option E: Option E is incorrect: escalating to high-dose methotrexate is inappropriate and dangerous in the setting of hepatotoxicity.
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