Gastroenterology Consultation

Reason for Consult

Acute flare of ileocolonic Crohn's disease with suspected secondary loss of response to adalimumab.

History of Present Illness

Marcus Vance is a 34-year-old male referred by Dr. Sarah Jenkins for management of worsening Crohn's disease symptoms.

He attends today to discuss an escalation in abdominal pain and diarrhea over the past 6 weeks, as well as optimization of his biologic therapy.

The primary reason for this consultation is to evaluate an acute flare of known ileocolonic Crohn's disease characterized by increased stool frequency, nocturnal symptoms, and cramping right lower quadrant (RLQ) abdominal pain.

The patient reports that his symptoms began gradually 6 weeks ago and have progressively worsened in severity. He currently experiences 6 to 8 loose, non-bloody bowel movements per day, including 1 to 2 nocturnal episodes. He describes moderate-to-severe RLQ cramping that is aggravated by meals and partially relieved by defecation. Associated symptoms include a 4 kg unintentional weight loss over the past month, low-grade subjective fevers, and worsening bilateral knee arthralgias. He was recently prescribed a 2-week course of budesonide by his primary care provider, which provided minimal relief, and remains on weekly adalimumab maintenance therapy.

Inflammatory Bowel Disease History

1. Diagnosis : Ileocolonic Crohn's disease (Montreal classification A2, L3, B1), diagnosed in 2018 at age 28.
2. Current Therapy: adalimumab (Humira®) 40 mg SC weekly and budesonide (Entocort®) 9 mg PO daily.
3. Prior therapy:

• azathioprine (Imuran®) — discontinued in 2019 due to drug-induced pancreatitis.
• infliximab (Remicade®) — discontinued in 2021 due to secondary loss of response and high-titer anti-drug antibodies.

4. Most Recent Colonoscopy:

• Performed on 12/11/2023.
• Showed moderate patchy erythema, aphthous ulcerations in the terminal ileum, and mild patchy colitis in the ascending colon (Simple Endoscopic Score for Crohn's Disease [SES-CD] of 8).
• Histopathology confirmed chronic active ileitis and colitis without dysplasia or granulomas.

5. Fecal Calprotectin: 680 µg/g on 02/04/2025 (elevated from baseline of 110 µg/g in 06/2024).
6. Surgical History:

• Incision and drainage of perianal abscess in 2018.
• Diagnostic laparoscopy and appendectomy in 2016.

7. Extraintestinal Manifestations: Peripheral arthropathy affecting the bilateral knees and ankles, and history of erythema nodosum (currently quiescent).

Past Medical History

1. Ileocolonic Crohn's disease.
2. Iron deficiency anemia.
3. Vitamin D deficiency.
4. Appendectomy (2016).

Medications

1. adalimumab (Humira®) 40 mg SC weekly.
2. budesonide (Entocort®) 9 mg PO daily.
3. colecalciferol (Vitamin D3) 2,000 IU PO daily.
4. ferrous fumarate (Palafer®) 300 mg PO daily.
5. paracetamol (acetaminophen, Tylenol®) 1,000 mg PO Q6H PRN.

Allergies

azathioprine (acute pancreatitis); NKDA to antibiotics or latex.

Social History

Lives with his wife and 2-year-old son in a single-family home.

Former smoker (quit in 2019, 5 pack-year history); drinks 1 to 2 standard alcoholic beverages per month; denies recreational drug use.

Works as a software engineer and resides in Toronto, ON.

Family History

Mother has rheumatoid arthritis; maternal uncle has ulcerative colitis; father has hypertension and T2DM; no family history of colorectal cancer.

Physical Exam

• Vital signs: BP 118/74 mmHg, HR 82 bpm, Temp 37.1 °C, Weight 68.5 kg, BMI 21.8 kg/m². General: Alert, oriented, appears mildly fatigued, NAD. Abdomen: Soft, non-distended, normoactive bowel sounds, moderate tenderness to palpation in the RLQ without rebound or guarding, no palpable masses or hepatosplenomegaly. Perianal: Healed scar at 7 o'clock position, no active fistulae, fissures, or fluctuance. MSK: Mild tenderness to palpation over bilateral knee joints without significant effusion.

Investigations

• Labs (02/04/2025): Hb 118 g/L, MCV 78 fL, WBC 10.8 x 10^9/L, Plt 415 x 10^9/L, CRP 28.4 mg/L, Albumin 34 g/L, Ferritin 18 µg/L. Stool cultures, C. difficile PCR, and ova and parasites negative. Adalimumab trough level (28/03/2025): 1.2 µg/mL (subtherapeutic) with positive anti-adalimumab antibodies.
• Colonoscopy (12/11/2023): Moderate ileocolonic Crohn's disease (SES-CD 8).
• Upper Endoscopy (15/05/2018): Normal esophagus, stomach, and duodenum; biopsies negative for H. pylori and upper GI Crohn's disease.
• MR Enterography (18/03/2025): 12 cm segment of active inflammation in the terminal ileum with mural thickening (6 mm) and mucosal hyperenhancement; no strictures, fistulae, or intra-abdominal abscesses identified.

Assessment and Plan

1. Acute Flare of Ileocolonic Crohn's Disease

The patient presents with an acute moderate-to-severe flare of ileocolonic Crohn's disease, evidenced by worsening diarrhea, RLQ pain, weight loss, elevated CRP (28.4 mg/L), elevated fecal calprotectin (680 µg/g), and active terminal ileitis on MRE. Therapeutic drug monitoring confirms secondary loss of response to adalimumab due to immunogenicity (low trough levels with positive anti-drug antibodies).

Differential diagnosis for the acute symptom exacerbation includes infectious enterocolitis (ruled out via negative stool studies and C. difficile PCR), fibrostenotic stricture (ruled out via recent MRE), or bile acid malabsorption.

• Schedule ileocolonoscopy in 6 months to assess mucosal healing following therapy switch; check baseline pre-biologic screening labs today including TB IGRA (QuantiFERON-TB Gold), Hepatitis B and C serologies, and lipid panel.
• Discontinue adalimumab and budesonide. Initiate prednisone 40 mg PO daily for 2 weeks, then taper by 5 mg weekly as a bridge. Transition maintenance therapy to risankizumab (Skyrizi®) 600 mg IV at weeks 0, 4, and 8, followed by 360 mg SC every 8 weeks to achieve clinical and endoscopic remission. Discussed rare risks including upper respiratory infections, injection site reactions, and hepatotoxicity.
• Advised a low-residue, low-fiber diet during the acute flare to minimize mechanical irritation and cramping; maintain strict smoking cessation; encourage regular low-impact physical activity as joint pain allows.
• Follow up in clinic in 6 weeks to evaluate clinical response to induction therapy and steroid taper, with repeat CBC, CRP, liver enzymes, and fecal calprotectin prior to the visit.
• Refer to the IBD nurse navigator for risankizumab patient support program enrollment and financial coverage coordination; refer to Registered Dietitian for nutritional optimization given recent weight loss.

2. Iron Deficiency Anemia

Secondary to chronic gastrointestinal blood loss and malabsorption from active Crohn's disease, complicated by poor tolerance and inadequate response to oral iron supplementation (Hb 118 g/L, Ferritin 18 µg/L).

Differential diagnosis includes anemia of chronic disease.

• Repeat CBC and ferritin levels in 8 weeks to assess marrow response.
• Discontinue oral ferrous fumarate to reduce GI side effects. Administer ferric derisomaltose (Monoferric®) 1,000 mg IV x 1 dose at the infusion clinic to replenish iron stores. Discussed small risk of hypersensitivity reaction and skin staining at the IV site.
• Counselled on incorporating iron-rich foods with vitamin C once acute flare subsides.
• Review laboratory response at the next scheduled GI follow-up appointment.
• Refer to outpatient medical day unit for IV iron infusion administration.

Additional Notes

• Discussed the pathophysiology of immunogenicity to anti-TNF agents and the mechanism of action of selective IL-23 inhibition with risankizumab. Emphasized the importance of adherence to the induction schedule and completing the steroid taper to prevent disease progression and structural bowel damage.
• Instructed the patient to monitor for red flag symptoms and to present to the nearest Emergency Department immediately if he develops severe unremitting abdominal pain, persistent vomiting, inability to pass gas or stool, high fever, or brisk hematochezia.
• Addressed the patient's concerns regarding the safety of switching biologics and the time required to achieve symptom relief; reassured him that bridging with systemic corticosteroids should provide rapid symptom control while risankizumab takes effect.