1. A 58-year-old man with rheumatoid arthritis has been on tofacitinib 5 mg twice daily for 14 months. He presents with a painful vesicular rash in a dermatomal distribution over his left thorax consistent with herpes zoster (shingles — reactivation of varicella-zoster virus from dorsal root ganglia). His primary care physician asks whether the patient should have received a zoster vaccine before starting tofacitinib, and which vaccine would have been appropriate. Which response is correct?

• A) Herpes zoster reactivation is not associated with tofacitinib; it is a well-known complication of TNF-alpha inhibitors due to their suppression of granulomatous containment of varicella-zoster virus in sensory ganglia, and the patient's zoster episode is therefore unrelated to his tofacitinib therapy and does not require a change in management.
• B) Zostavax, the live attenuated zoster vaccine, should be administered now during tofacitinib therapy to reduce the risk of future zoster episodes; live attenuated vaccines are safe during tofacitinib treatment because tofacitinib's JAK3 selectivity spares innate immune function and does not impair the vaccine-induced T-cell response to the attenuated viral antigen.
• C) Zoster vaccination is not recommended for patients on JAK inhibitors because the vaccine produces subclinical varicella-zoster virus viremia that the immunosuppressed patient cannot control; if zoster reactivation occurs during tofacitinib therapy, the appropriate response is to increase the dose of tofacitinib to suppress the inflammatory component of the zoster episode.
• D) The preferred approach is to administer the live attenuated zoster vaccine (Zostavax) at least two weeks before starting tofacitinib; Zostavax provides equivalent protection to the recombinant subunit vaccine and is the only option approved for use prior to JAK inhibitor initiation.
• E) Herpes zoster reactivation is a recognized class-wide risk of JAK inhibitors including tofacitinib, attributed in part to impairment of IL-15-dependent and IL-2-dependent maintenance of CD8 memory T cells that normally suppress varicella-zoster virus reactivation; the preferred zoster vaccine before or during JAK inhibitor therapy is Shingrix (recombinant zoster vaccine, adjuvanted), a non-live subunit vaccine that can be given safely even during immunosuppression; Zostavax (live attenuated) is contraindicated during active JAK inhibitor therapy and should be administered, if used at all, at least four weeks before starting immunosuppression.

2. A 34-year-old woman is referred jointly to a dermatologist and gastroenterologist. She has moderate-to-severe plaque psoriasis covering approximately 25% of her body surface area and active Crohn's disease with ileocolonic involvement that has failed mesalamine. She requires a single biologic agent that will address both conditions. Which agent and rationale represent the most appropriate selection?

• A) Secukinumab (anti-IL-17A monoclonal antibody) is the most appropriate choice because IL-17A drives both the keratinocyte hyperproliferation in psoriatic plaques and the intestinal epithelial inflammation in Crohn's disease; blocking IL-17A therefore addresses both conditions through a single shared pathogenic cytokine with robust clinical evidence in both indications.
• B) Risankizumab (selective IL-23 p19 inhibitor) is the most appropriate choice; it is approved for both moderate-to-severe plaque psoriasis and Crohn's disease, and its selective blockade of IL-23 — which drives Th17 expansion in both skin and gut — addresses both conditions while preserving IL-12-driven Th1 immunity; IL-17A inhibitors such as secukinumab and ixekizumab carry a class-specific risk of new-onset or exacerbated IBD and are contraindicated or used with extreme caution in patients with active Crohn's disease.
• C) Adalimumab (fully human anti-TNF-alpha IgG1 monoclonal antibody) is the most appropriate choice because TNF-alpha is the single cytokine most central to both psoriatic and intestinal inflammation; as a fully human antibody, adalimumab avoids the anti-drug antibody formation associated with chimeric biologics such as infliximab, making it the preferred TNF inhibitor for long-term dual-indication use in a young woman of childbearing age.
• D) Upadacitinib (selective JAK1 inhibitor) is the most appropriate choice; it is approved for both psoriatic arthritis and Crohn's disease and provides oral administration, which this patient may prefer over subcutaneous injections; because upadacitinib's JAK1 selectivity spares the JAK2-dependent hematopoietic growth factor pathways, it carries a more favorable safety profile for long-term use than broader JAK inhibitors.
• E) Methotrexate combined with a biologic is required for both conditions; monotherapy with any single biologic is pharmacologically insufficient to control both moderate-to-severe psoriasis and active Crohn's disease simultaneously, and current guidelines mandate methotrexate co-administration to prevent anti-drug antibody formation and maintain biologic drug levels in patients requiring dual-indication treatment.

3. A 67-year-old man with a myocardial infarction 18 months ago remains on high-intensity rosuvastatin with LDL 58 mg/dL but has persistently elevated high-sensitivity C-reactive protein (hsCRP) of 3.4 mg/L. His cardiologist considers adding canakinumab (anti-IL-1 beta monoclonal antibody) for residual inflammatory cardiovascular risk based on CANTOS trial data. Before initiating canakinumab, which pre-treatment evaluation is mandatory regardless of the patient's apparent good health?

• A) Latent tuberculosis screening using either a tuberculin skin test (TST/PPD) or an interferon-gamma release assay (IGRA such as QuantiFERON-TB Gold), and hepatitis B serology including hepatitis B surface antigen (HBsAg) and total hepatitis B core antibody (anti-HBc), are both required before initiating canakinumab; these screens are mandatory before any immunosuppressive biologic because IL-1 beta blockade — like all biologic immunosuppression — can permit reactivation of latent Mycobacterium tuberculosis and latent hepatitis B virus in patients with prior unrecognized exposure, with potentially life-threatening consequences.
• B) Echocardiography and coronary angiography are required before initiating canakinumab because the drug's anti-inflammatory mechanism may mask ischemic symptoms by reducing CRP-driven anginal pain signaling; baseline cardiac imaging is therefore mandatory to document any subclinical ischemia that might be clinically silent during canakinumab therapy.
• C) Complete blood count with differential is the only mandatory pre-treatment test; canakinumab's selective IL-1 beta blockade does not impair T-cell or macrophage function, so infectious screening is unnecessary; the CBC is required because IL-1 beta promotes hematopoiesis and its blockade may cause neutropenia during the first 4 weeks of therapy.
• D) HIV serology and CD4 T-lymphocyte count are the only required pre-treatment screens; IL-1 beta blockade specifically impairs HIV viral load containment because IL-1 beta drives CD8 cytotoxic T-lymphocyte expansion against HIV-infected cells, and pre-existing undiagnosed HIV infection combined with canakinumab therapy can result in rapid CD4 cell depletion.
• E) No specific pre-treatment infectious screening is required before canakinumab in a cardiovascular indication; while tuberculosis and hepatitis B screening are required before TNF-alpha inhibitors and JAK inhibitors used for autoimmune diseases, the cardiovascular indication for canakinumab involves lower doses that do not produce sufficient immunosuppression to pose reactivation risk, and the FDA label does not mandate infectious screening for the MACE-reduction indication.

4. A 45-year-old woman with PNH has been on eculizumab for 3 years. Before starting eculizumab she received MenACWY (quadrivalent meningococcal conjugate vaccine). She now presents to the emergency department with fever, severe headache, neck stiffness, and photophobia. Lumbar puncture confirms bacterial meningitis, and blood cultures grow Neisseria meningitidis serogroup B. A review of her vaccination history reveals she never received a meningococcal serogroup B vaccine. Which statement most accurately identifies the preventable gap in her pre-treatment management?

• A) The vaccination gap is not clinically relevant; N. meningitidis serogroup B meningitis in a PNH patient on eculizumab reflects an expected limitation of all complement inhibitors, and the FDA label requires only MenACWY vaccination before eculizumab initiation; serogroup B vaccination is listed as optional in guidelines because MenB vaccines were not widely available when eculizumab was first approved.
• B) The preventable gap was failure to check serum complement levels (CH50 — total hemolytic complement activity) before initiating eculizumab; a low CH50 prior to therapy would have identified this patient as having pre-existing terminal complement pathway dysfunction and therefore at higher risk for encapsulated organism infection even before drug therapy began.
• C) The preventable gap was the dose interval of eculizumab; the standard every-2-week infusion schedule allows transient recovery of C5 activity in the final 48–72 hours before each dose, creating a window during which meningococcal invasion can occur; more frequent dosing or switching to ravulizumab's every-8-week schedule would have eliminated this vulnerability.
• D) The preventable gap was failure to administer meningococcal serogroup B vaccine (MenB) before initiating eculizumab; the FDA-labeled black box warning for eculizumab requires vaccination with BOTH MenACWY (which covers serogroups A, C, W, and Y) AND a meningococcal serogroup B vaccine (such as MenB-FHbp or MenB-4C) at least two weeks before the first eculizumab dose, because N. meningitidis serogroup B is the predominant cause of meningococcal disease in many developed countries and is not covered by MenACWY; many centers also prescribe indefinite penicillin prophylaxis throughout eculizumab therapy.
• E) The preventable gap was failure to obtain pre-treatment nasopharyngeal culture for N. meningitidis carrier state; patients who are asymptomatic meningococcal carriers at the time eculizumab is initiated are at dramatically higher risk for invasive meningococcal disease, and mandatory eradication therapy with rifampin should have been completed before beginning eculizumab regardless of vaccination status.

5. A 29-year-old woman with rheumatoid arthritis has been on adalimumab 40 mg subcutaneously every two weeks throughout her pregnancy. She delivers a healthy male infant at 36 weeks gestation. The neonatology team is preparing a discharge vaccination plan. The family recently emigrated from a country where BCG vaccination (bacille Calmette-Guérin, a live attenuated Mycobacterium bovis vaccine) is given at birth, and the parents request it be administered. Which recommendation regarding BCG vaccination is most appropriate, and what pharmacological property of adalimumab drives this recommendation?

• A) BCG vaccination can be safely administered at birth because adalimumab does not cross the placenta; as a large molecular weight IgG1 antibody, adalimumab is excluded from placental transfer by size exclusion at the syncytiotrophoblast barrier, and cord blood adalimumab concentrations are negligible at delivery regardless of gestational age at last dose.
• B) BCG vaccination should be delayed until 4 weeks of age because adalimumab's half-life in the neonate is approximately 3–4 days; waiting 4 weeks allows at least 6 half-lives for drug clearance, restoring sufficient immune function for safe live vaccine administration to the infant.
• C) BCG vaccination should be withheld for at least 6 months after birth because adalimumab, an IgG1 Fc-containing monoclonal antibody, undergoes active placental transfer via FcRn (neonatal Fc receptor) on syncytiotrophoblasts, with transfer increasing substantially in the third trimester; cord blood adalimumab concentrations may equal or exceed maternal levels at delivery, creating a state of TNF-alpha blockade in the neonate that persists for weeks to months; live attenuated vaccines including BCG are contraindicated during this period because the immunosuppressed infant may develop disseminated BCGosis — a potentially fatal complication of disseminated vaccine-strain mycobacterial infection.
• D) BCG can be administered immediately because the infant is premature at 36 weeks and premature infants have immature Fc receptor expression in the gut and reticuloendothelial system; this immaturity prevents the infant from absorbing or systemically distributing any maternally transferred IgG including adalimumab, making the neonate functionally free of drug regardless of maternal exposure timing.
• E) BCG should be given at birth because adalimumab's mechanism — TNF-alpha neutralization — specifically protects against BCGosis; TNF-alpha is required for the excessive inflammatory response that causes tissue damage in disseminated BCG infection, and blocking TNF-alpha with maternally transferred adalimumab would prevent the pathological inflammatory cascade if vaccine-strain dissemination occurred, making BCG vaccination safer, not less safe, in this setting.

6. A 52-year-old woman with severe atopic dermatitis started dupilumab 6 weeks ago with excellent skin improvement. She now returns with bilateral eye redness, irritation, and a mucoid discharge. Slit-lamp examination shows conjunctival injection and mild papillary changes without corneal involvement. She asks whether she must stop dupilumab. Which response most accurately identifies the nature of this complication and its management?

• A) This presentation is consistent with dupilumab-associated conjunctivitis, which occurs because dupilumab blocks IL-4Ralpha and inadvertently suppresses the IL-4-dependent secretory IgA production in the conjunctival mucosa; the resulting secretory IgA deficiency allows bacterial overgrowth on the ocular surface; treatment requires dupilumab discontinuation and a 2-week course of topical antibiotic drops.
• B) Dupilumab-associated conjunctivitis is the most common adverse effect of dupilumab, occurring in approximately 10 to 25% of atopic dermatitis patients, and is thought to involve altered IL-4 and IL-13 signaling in the ocular mucosal environment — potentially affecting goblet cell function, conjunctival mucin composition, or Demodex mite colonization; dupilumab discontinuation is not required for this complication; management includes topical ophthalmic cyclosporine or tacrolimus, lubricating eye drops, and ophthalmology referral if severe, while continuing dupilumab with monitoring.
• C) This is a hypersensitivity reaction to the dupilumab excipient polysorbate 80 affecting the ocular mucosa; it develops predictably 4 to 8 weeks after injection initiation as delayed-type hypersensitivity responses mature; dupilumab must be permanently discontinued and the patient should be switched to an alternative IL-4Ralpha blocking agent with a different excipient formulation.
• D) The conjunctivitis reflects paradoxical worsening of atopic disease in the eye driven by the shift in type 2 cytokine balance induced by skin-targeted dupilumab therapy; by suppressing IL-4 and IL-13 in skin, dupilumab causes compensatory upregulation of these cytokines at other mucosal surfaces including the conjunctiva, and dose reduction to every-4-week injection intervals reduces the compensatory cytokine surge and resolves ocular symptoms.
• E) This represents viral conjunctivitis unrelated to dupilumab; dupilumab's IL-4Ralpha blockade impairs conjunctival secretory IgA-mediated antiviral defense, and adenoviral conjunctivitis is the expected infectious complication; the patient requires antiviral eye drops and temporary isolation, and dupilumab should be held until the adenoviral infection resolves.

7. A 41-year-old woman with rheumatoid arthritis has been on baricitinib 4 mg daily for 8 months with good disease control. She presents with right calf pain and swelling; duplex ultrasound confirms acute deep vein thrombosis (DVT) of the right popliteal vein. She has no prior VTE history, no inherited thrombophilia, and no other identifiable provoking factors. Which management approach best integrates the pharmacological explanation for this complication with appropriate ongoing RA therapy?

• A) Baricitinib should be continued at the current dose because the DVT is provoked by RA-related immobility rather than by the drug; anticoagulation with apixaban should be initiated for the DVT, and baricitinib should be continued to maintain RA disease control, as discontinuing the drug would risk a disease flare that could further increase VTE risk through inflammatory hypercoagulability.
• B) Baricitinib should be dose-reduced from 4 mg to 2 mg daily while initiating anticoagulation; the 2 mg dose produces less JAK1 inhibition and therefore less suppression of the plasminogen activator inhibitor-1 (PAI-1) transcription pathway that drives VTE, and the reduced dose retains sufficient JAK2 activity to maintain adequate RA control without the thrombotic risk of the higher dose.
• C) Baricitinib should be continued but a direct-acting oral anticoagulant (DOAC) added indefinitely; because baricitinib's VTE risk is a class-wide pharmacodynamic effect that persists as long as the drug is taken, indefinite anticoagulation while continuing baricitinib is the recommended management for drug-associated VTE rather than switching to an alternative RA biologic.
• D) Baricitinib should be discontinued because JAK inhibitors carry a class-wide FDA black box warning for venous thromboembolism — attributed mechanistically to JAK2-dependent thrombopoietin signaling alteration and potential STAT3-mediated suppression of anticoagulant gene transcription — and this patient's unprovoked DVT occurring on baricitinib represents a drug-attributed adverse event; anticoagulation with a DOAC should be initiated for the DVT, and RA therapy should be transitioned to an alternative biologic class such as a TNF inhibitor or IL-6 receptor inhibitor that does not carry the same VTE risk profile.
• E) The DVT is most likely unrelated to baricitinib because the VTE risk in the ORAL Surveillance trial was observed only with tofacitinib, not with baricitinib; because baricitinib's JAK2 selectivity theoretically reduces platelet activation risk compared to JAK3-preferring inhibitors, the DVT should be attributed to underlying RA hypercoagulability, and baricitinib should be continued while anticoagulation is initiated.

8. A 63-year-old woman with giant cell arteritis (GCA — a large-vessel vasculitis affecting the aorta and its branches) has been on tocilizumab 162 mg subcutaneously weekly for 11 months with excellent disease control and normalized inflammatory markers. She presents to the emergency department with 3 days of fever to 38.9 degrees C, productive cough, and dyspnea. Her CRP returns as less than 0.3 mg/L (undetectable). A resident interprets this as reassuring and considers discharging the patient with oral antibiotics for mild pneumonia. Which pharmacological explanation should modify this clinical reasoning?

• A) A normal or undetectable CRP in this patient is expected and clinically uninterpretable as a marker of infection severity because tocilizumab blocks the IL-6 receptor, abolishing IL-6-driven hepatic CRP synthesis; CRP cannot be used as an infection biomarker in patients on IL-6 receptor inhibitors regardless of the severity of the underlying infection — a patient with life-threatening sepsis may have an undetectable CRP while on tocilizumab; infection severity must be assessed through clinical examination, vital signs, chest imaging, complete blood count, and procalcitonin (PCT — a sepsis biomarker driven primarily by bacterial endotoxin and IL-1/TNF pathways rather than IL-6, and therefore less suppressed by tocilizumab).
• B) The undetectable CRP confirms that this patient does not have a significant bacterial infection; because IL-6 is the primary driver of the CRP elevation seen in bacterial infections, an undetectable CRP in a patient on tocilizumab indicates that no IL-6-generating bacterial process is present; the resident's reassurance is pharmacologically justified, and the patient can be safely discharged.
• C) The undetectable CRP is concerning because it indicates that tocilizumab has depleted the patient's available acute-phase protein pool; patients on long-term tocilizumab develop hepatic acute-phase protein depletion syndrome, in which the liver loses the ability to upregulate any acute-phase proteins including fibrinogen, complement, and ferritin, creating a paradoxical vulnerability to infection progression despite the absence of inflammatory markers.
• D) CRP suppression by tocilizumab is incomplete and dose-dependent; at the standard 162 mg subcutaneous weekly dose, tocilizumab achieves approximately 50% CRP suppression in most patients; an undetectable CRP at this dose therefore indicates that the true underlying CRP is also very low and reflects a mild infection unlikely to require hospitalization.
• E) The resident's reasoning is correct; CRP remains a reliable infection biomarker in patients on IL-6 receptor inhibitors because CRP synthesis in the setting of significant bacterial infection is driven by IL-1 beta and TNF-alpha in addition to IL-6, and these alternative pathways are unaffected by tocilizumab; only in sterile inflammatory conditions (such as vasculitis flares) does IL-6 account for the majority of CRP elevation.

9. A 38-year-old woman with hereditary angioedema (HAE — recurrent attacks of subcutaneous and submucosal swelling caused by C1-INH deficiency and excess bradykinin generation) was started on lanadelumab 300 mg subcutaneously every 4 weeks as long-term prophylaxis 6 months ago. Her attack frequency decreased from approximately 3 attacks per month to 1 attack every 6 weeks. She now presents to the emergency department with acute facial and tongue swelling that began 2 hours ago. She asks why prophylaxis "stopped working." Which pharmacological explanation and management recommendation is most appropriate?

• A) Lanadelumab has lost efficacy due to anti-drug antibody (ADA) formation, a common complication occurring in approximately 40% of patients after 6 months of therapy; the appropriate response is to immediately switch to a different prophylactic agent (berotralstat, an oral plasma kallikrein inhibitor), discontinue lanadelumab, and manage this acute attack with intravenous icatibant at double the standard subcutaneous dose.
• B) This acute attack indicates that lanadelumab prophylaxis has failed completely and should be discontinued; lanadelumab is effective only during the first 3 to 6 months of therapy before HAE physiology adapts through upregulation of alternative kinin-generating pathways; a switch to C1-INH concentrate for both acute treatment and long-term replacement therapy is the appropriate response to lanadelumab secondary failure.
• C) The acute attack represents a rebound bradykinin surge caused by intermittent plasma kallikrein blockade; lanadelumab's every-4-week dosing creates pre-dose troughs in which plasma kallikrein activity recovers fully, and attacks during this period are physiologically more severe than untreated attacks; dosing should be increased to every 2 weeks, and this acute attack should be managed with high-dose corticosteroids and antihistamines.
• D) The acute attack should be managed conservatively with observation only; lanadelumab serum concentrations are maintained above therapeutic threshold throughout the 4-week dosing interval, and any swelling occurring while on adequate prophylaxis is not HAE but rather allergic angioedema driven by IgE-mediated histamine release — the appropriate treatment is intramuscular epinephrine and antihistamines rather than bradykinin pathway-targeted therapies.
• E) HAE prophylaxis with lanadelumab reduces attack frequency but does not guarantee complete attack elimination; breakthrough attacks can occur despite adequate prophylaxis for reasons including physiological triggers (stress, minor trauma, hormonal changes) that overwhelm the plasma kallikrein inhibition; this acute attack is a true HAE episode requiring immediate acute rescue therapy — icatibant (a subcutaneous bradykinin B2 receptor antagonist) or C1-INH concentrate (plasma-derived or recombinant) should be administered promptly for the acute attack while continuing lanadelumab prophylaxis; the patient should always carry acute rescue medication even while on prophylaxis.

10. A 72-year-old man with atypical hemolytic uremic syndrome (aHUS — a rare thrombotic microangiopathy driven by uncontrolled alternative complement pathway activation) has been on eculizumab infusions every 2 weeks for 4 years with stable renal function (serum creatinine 1.4 mg/dL, no active hemolysis). His orthopedic surgeon schedules elective total hip replacement and asks the patient's nephrologist whether eculizumab should be held perioperatively to reduce infection risk from complement blockade during surgery. Which pharmacological reasoning best guides the perioperative management of eculizumab?

• A) Eculizumab should be held for 4 weeks before surgery and resumed 2 weeks postoperatively; complement activity is required for optimal wound healing through C3b-mediated clearance of apoptotic cells and surgical debris from the operative field, and maintaining complement blockade throughout the perioperative period impairs tissue repair and increases the risk of wound infection and dehiscence.
• B) Eculizumab should be permanently discontinued before elective surgery in aHUS patients with stable renal function for greater than 2 years; sustained complement suppression leads to compensatory upregulation of alternative pathway regulators, and patients who have been on eculizumab for more than 2 years typically maintain adequate complement control through these upregulated endogenous mechanisms without ongoing drug therapy.
• C) Eculizumab dosing frequency should be increased to daily intravenous infusions for 1 week before and 1 week after surgery; surgical tissue injury dramatically amplifies complement activation through the release of damage-associated molecular patterns (DAMPs), requiring supra-therapeutic complement blockade to prevent perioperative aHUS flare; standard every-2-week dosing is insufficient to cover the perioperative period.
• D) Eculizumab should be continued through the perioperative period without interruption because surgical stress, anesthesia, tissue injury, and blood loss activate the complement system through damage-associated molecular patterns and ischemia-reperfusion pathways; in a patient whose aHUS is driven by uncontrolled alternative pathway activation, perioperative complement activation poses a significant risk of triggering thrombotic microangiopathy (TMA) with acute kidney injury, which could be catastrophic in a patient with already compromised renal function; prophylactic antibiotics should be provided, and hematology and nephrology should coordinate perioperative monitoring for signs of TMA including hemoglobin, platelet count, LDH, and creatinine.
• E) The surgical team should contact the eculizumab manufacturer to obtain emergency perioperative complement activity testing (CH50 assay) before each procedure; if CH50 is greater than 10% of normal, an additional eculizumab dose should be given the day before surgery; if CH50 is less than 10%, standard complement blockade is adequate and no additional dosing is required; eculizumab should be held for 72 hours postoperatively to allow complement-mediated antimicrobial defense during the highest infection-risk period.

11. A 55-year-old man with ankylosing spondylitis (AS — a chronic inflammatory arthritis of the spine and sacroiliac joints) has failed adalimumab and golimumab due to secondary loss of efficacy. His rheumatologist is considering ixekizumab (an anti-IL-17A monoclonal antibody approved for AS). Before prescribing, she reviews his history and notes he has ulcerative colitis diagnosed 4 years ago, currently in endoscopic remission on mesalamine. Which pharmacological consideration most directly influences the prescribing decision?

• A) Ixekizumab is the preferred choice for this patient because IL-17A drives both the enthesitis (inflammation at tendon/ligament bone attachment sites) and gut mucosal inflammation characteristic of spondyloarthropathy-associated IBD; blocking IL-17A simultaneously addresses both the AS and the underlying IBD inflammation, making ixekizumab superior to TNF inhibitors for patients with the axial spondyloarthropathy-IBD overlap phenotype.
• B) Ixekizumab can be initiated at a reduced dose in patients with quiescent IBD; the standard induction dose should be halved to reduce the risk of IBD exacerbation during the first 16 weeks while AS control is established; once AS is controlled, the standard maintenance dose can be resumed with close gastrointestinal monitoring.
• C) Ixekizumab should be avoided in this patient because IL-17A inhibitors carry a class-specific risk of new-onset or exacerbated inflammatory bowel disease; clinical trials have demonstrated that IL-17A inhibitors (secukinumab, ixekizumab) are not effective in IBD and may worsen it, and patients with pre-existing IBD — even in remission — are at significant risk for disease exacerbation during IL-17A inhibitor therapy; alternative options for AS with co-existing IBD include TNF inhibitors (infliximab or adalimumab, both approved for AS and IBD) or ustekinumab (approved for AS-related psoriatic arthritis and IBD, used off-label in AS), while recognizing that the patient has already failed two TNF inhibitors.
• D) The UC history is not a contraindication to ixekizumab when IBD is in endoscopic remission; the IBD risk with IL-17A inhibitors applies only to patients with active luminal disease (defined as Mayo endoscopic score 2 or higher); patients in endoscopic remission — as confirmed for this patient — are not at elevated risk for IBD exacerbation from IL-17A inhibition.
• E) Ixekizumab's IBD risk is limited to new-onset Crohn's disease and does not apply to patients with ulcerative colitis; the pathogenic mechanism by which IL-17A inhibition triggers IBD involves granulomatous Th1 inflammation specifically relevant to Crohn's disease pathophysiology, and patients with pre-existing UC have a distinct disease mechanism that is unaffected by IL-17A blockade.