Two separate investigators have conducted cohort studies to calculate the risk of lymphoma in rheumatoid arthritis patients taking anti-TNF alpha medications. They each followed patients with rheumatoid arthritis for a number of years and tracked the number of patients who were diagnosed with lymphoma. The results of the two studies are summarized in the table. Number of patients Follow-up period Number of new cases of lymphoma Study 1 3000 10 years 30 Study 2 300 30 years 9 Based on these results, which of the following statements about the risk of lymphoma is most accurate?

The risks are equivalent, with an incidence rate of 1 case per 1000 person-years

The risk is higher in study 1, with an incidence rate of 30 cases per 10 person-years

The risks are equivalent, with a prevalence of 39 cases per 3300 persons

The risk is higher in study 1, with a prevalence of 30 cases per 3000 patients

The risk is higher in study 2, with a cumulative incidence of 9 cases per 300 patients

A 46-year-old male presents to his dermatologist for routine follow-up of his psoriasis. He was last seen in the office six months prior, at which time he started undergoing ultraviolet light therapy. He reports that he initially noticed an improvement in his symptoms but the effects were transient. He has also started noticing pain and stiffness in his fingers. His past medical history is notable for obesity and diabetes mellitus. He takes metformin. His temperature is 99°F (37.2°C), blood pressure is 130/80 mmHg, pulse is 80/min, and respirations are 16/min. Multiple plaques with scaling are noted on the extensor surfaces of the upper and lower extremities. The patient’s physician suggests stopping the ultraviolet light therapy and starting an injectable medication that acts as a decoy receptor for a pro-inflammatory cytokine. Which of the following is an adverse effect associated with the use of this medication?

Reactivation of latent tuberculosis

A 53-year-old woman presents to her primary care physician with complaints of pain and swelling in her hands and fingers. She states that she has had these symptoms since she was in her 20s, but they have recently become more severe. She states that her wedding ring no longer fits, due to increased swelling of her fingers. She is a 30-pack-year smoker with a body mass index (BMI) of 31 kg/m2. The vital signs include: blood pressure 122/78 mm Hg, heart rate 72/min, and respiratory rate 15/min. On physical exam, a mild systolic murmur is heard over the apex, and her lungs are clear bilaterally. There is swelling of all the digits bilaterally, and a yellow-white plaque is noted beneath 3 of her nail beds. When asked about the plaques, she states that she was given itraconazole for them about 3 weeks ago; however, the plaques did not resolve. When asked further about joint pain, she notes that she has had shoulder and knee pain for the last several years, although she has not sought medical care for this. Which of the following is the best initial step in this patient’s therapeutic management?

Administer indomethacin and methotrexate

Administer indomethacin and sulfasalazine

A 53-year-old woman presents to her primary care provider complaining of fatigue for the last several months. She reports feeling tired all day, regardless of her quality or quantity of sleep. On further questioning, she has also noted constipation and a 4.5 kg (10 lb) weight gain. She denies shortness of breath, chest pain, lightheadedness, or blood in her stool. At the doctor’s office, the vital signs include: pulse 58/min, blood pressure 104/68 mm Hg, and oxygen saturation 98% on room air. The physical exam shows only slightly dry skin. The complete blood count (CBC) is within normal limits. Which of the following best describes the pathogenesis of this patient's condition?

Autoimmune attack on endocrine tissue

A 42-year-old woman presents complaining of pain in her hands. She reports that the pain is in both hands, and that it is usually worse in the morning. She reports that her hands are also stiff in the morning, but that this gradually improves throughout the morning. She notes, however, that her symptoms seem to be getting worse over the last three months. What is the most likely pathogenesis of her disease process?

Production of antibodies against antibodies

Production of antibodies against smooth muscle

Anti-neutrophil cytoplasmic antibody production

Type 1 hypersensitivity reaction

DMARDs and biologic therapies for USMLE Step 3: High-Yield Internal Medicine Lessons

DMARDs Overview - The Immune Arsenal

Goal: Slow/halt autoimmune disease progression (e.g., RA), reducing joint damage.
Classes:
- Conventional Synthetic (csDMARDs): Broad immunosuppression.
  - Methotrexate (MTX), Leflunomide, Sulfasalazine, Hydroxychloroquine.
- Biologic (bDMARDs): Targeted cytokine/cell inhibition.
  - TNF-α inhibitors (Adalimumab), IL-6 inhibitors (Tocilizumab).
- Targeted Synthetic (tsDMARDs): Small molecule inhibitors.
  - JAK inhibitors (Tofacitinib).

DMARD targets in immune cascade

⭐ All patients must be screened for latent Tuberculosis (TB) with a PPD or IGRA test before initiating most bDMARDs due to risk of reactivation.

csDMARDs - The Classic Crew

Conventional synthetic DMARDs are a cornerstone of RA therapy, working broadly to suppress the overactive immune system. They require regular monitoring due to potential toxicities.

Drug	Mechanism of Action (MOA)	Key Adverse Effects (ADEs)	Monitoring
Methotrexate	Dihydrofolate reductase inhibitor	Hepatotoxicity, pulmonary fibrosis, myelosuppression, stomatitis	CBC, LFTs, PFTs
Leflunomide	Dihydroorotate dehydrogenase inhibitor	Hepatotoxicity, teratogenicity, hypertension	LFTs, BP, pregnancy test
Sulfasalazine	Unclear; likely inhibits cytokine production	Hemolysis in G6PD deficiency, rash, reversible oligospermia	CBC, LFTs, G6PD screen
Hydroxychloroquine	Toll-like receptor (TLR) inhibitor	Irreversible retinal toxicity, corneal deposits	Annual eye exam

📌 Mnemonic: For Methotrexate, think "Metho-Trex-ate my Lungs, Liver, and Bone Marrow."

bDMARDs (TNF-α Inhibitors) - Tumor Necrosis Takedown

The "-mabs" & a "-cept":
- Infliximab
- Adalimumab
- Golimumab
- Certolizumab pegol
- Etanercept
⚠️ Class-Wide Black Box Warnings:
- Reactivation of latent infections, especially TB & Hepatitis B.
- ↑ Risk for invasive fungal infections (e.g., histoplasmosis).
- New onset or exacerbation of demyelinating disease (e.g., MS-like).
- Worsening heart failure (contraindicated in NYHA Class III/IV).

⭐ Etanercept is a decoy TNF receptor (a fusion protein), not a true monoclonal antibody like the other agents.

Other Biologics & tsDMARDs - The Precision Players

Beyond TNF-α inhibitors, a range of targeted therapies offers precision by interfering with specific immune pathways. These agents are typically reserved for moderate-to-severe disease refractory to conventional DMARDs and anti-TNF biologics.

Drug Class	Mechanism of Action (MOA)	Unique High-Yield Side Effects
Rituximab	Anti-CD20 mAb → Depletes B-cells	⚠️ PML, infusion reactions, Hep B reactivation
Abatacept	CTLA-4 Ig → Inhibits T-cell co-stimulation	⚠️ Caution in COPD (exacerbations)
Tocilizumab	Anti-IL-6R mAb → Blocks IL-6 signaling	⚠️ Bowel perforation, dyslipidemia, neutropenia
Tofacitinib	JAK Inhibitor (tsDMARD) → Blocks cytokine signals	⚠️ Thrombosis (VTE), ↑ Herpes Zoster risk

High‑Yield Points - ⚡ Biggest Takeaways

Methotrexate (MTX), the first-line DMARD for RA, causes hepatotoxicity and myelosuppression; requires folate supplementation.

Always screen for latent TB before starting TNF-α inhibitors (e.g., infliximab, etanercept) to prevent disease reactivation.

Hydroxychloroquine requires regular eye exams to screen for its dose-dependent, irreversible retinopathy.

Leflunomide is a potent teratogen and can cause severe liver injury.

All immunosuppressive therapies increase infection risk; live vaccines are contraindicated during treatment.

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