In a 13-year-old female with chronic diarrhea for 3–4 months and colonoscopy showing transmural inflammation consistent with Crohn disease, what is the preferred first‑line therapy for induction of remission?

First-Line Treatment for Pediatric Crohn's Disease with Transmural Inflammation

In a 13-year-old female with chronic diarrhea and colonoscopy showing transmural inflamed patches consistent with Crohn's disease, systemic corticosteroids (prednisone/prednisolone 1 mg/kg once daily up to 40 mg) are the first-line treatment for rapid induction of remission, unless high-risk features are present that would warrant immediate anti-TNF therapy. 1, 2

Risk Stratification Determines Initial Therapy

The critical first step is determining whether this patient has high-risk features that would shift management from corticosteroids to immediate biologic therapy:

High-risk features include: 1, 2

• Perianal disease or significant fistulizing disease
• Severe growth retardation (especially in Tanner stages 2-3)
• Deep ulcerations on endoscopy
• Extensive disease involving upper GI tract and proximal small bowel
• Need for corticosteroids at diagnosis (which this patient has)

If high-risk features are absent and disease is mild-to-moderate isolated ileocecal:

• 12-week course of budesonide (3-9 mg/day) is appropriate 1
• May add 5-ASA (50-80 mg/kg/day up to 4g daily) or antibiotics as adjuncts 1

If high-risk features are present:

• Early anti-TNF therapy (infliximab) should be initiated immediately rather than waiting for corticosteroid failure 2
• This approach is supported by evidence showing comparable 12-week remission rates between corticosteroids and anti-TNF, but superior long-term outcomes with early biologic use in high-risk patients 2

Why Systemic Corticosteroids Are First-Line (When Appropriate)

Systemic corticosteroids produce clinical improvement within days to weeks in the majority of pediatric Crohn's disease patients and are the most effective agents for rapidly inducing remission. 2 The standard regimen is prednisone/prednisolone 1 mg/kg once daily (maximum 40 mg) tapered over approximately 10 weeks. 1

Critical caveat: Repeated steroid courses or steroid dependency should not be tolerated—corticosteroids are for induction only, never maintenance. 1, 2

Why Other Options Are Not First-Line

Infliximab (Option B):

• Reserved for high-risk patients or those who fail corticosteroids 1, 2
• While effective, it is not routinely used as first-line unless risk stratification indicates immediate need 2
• FDA-approved for pediatric Crohn's at 5 mg/kg at weeks 0,2, and 6, then every 8 weeks 3

Methotrexate (Option C):

• Second-line agent for maintenance or after thiopurine failure 1
• Typical onset of action is 2-3 months, making it unsuitable for acute induction 1
• Dose is 15 mg/m² (max 25 mg) once weekly subcutaneously or intramuscularly 1

Nutritional management (Option D):

• Exclusive enteral nutrition (EEN) can induce remission in pediatric Crohn's disease 1
• However, it is not considered first-line pharmacologic therapy in most guidelines
• May be used as adjunctive therapy or in specific clinical scenarios where medication is contraindicated

Maintenance Strategy After Induction

Once remission is achieved with corticosteroids, transition to maintenance therapy is essential:

For most patients:

• Thiopurines (azathioprine 2-2.5 mg/kg/day or 6-mercaptopurine 1-1.5 mg/kg/day) with typical onset of action at 8-14 weeks 1
• Monitor CBC and liver enzymes closely 1

For high-risk patients:

• Continue or initiate anti-TNF therapy as maintenance 2
• Consider combination therapy with thiopurines in thiopurine-naïve patients, though this increases malignancy and infection risk 1

Monitoring and Follow-Up

• Ileocolonoscopy at 6-9 months post-induction to verify mucosal healing 2
• Clinical assessment every 3 months using PRO-2 scoring 1
• Serial fecal calprotectin and CRP monitoring 1
• MR enterography for transmural healing assessment (preferred over CT to avoid radiation in children) 1

Answer: A - Systemic steroid is the correct first-line option for this 13-year-old with newly diagnosed Crohn's disease showing transmural inflammation, assuming no high-risk features are present that would necessitate immediate anti-TNF therapy.