Immune system knowledge checks

Home » Immune System and Rheumatology » Immune system knowledge checks
Headshot of Sonam Kiwalkar, MD, FACP, MEHP · Endocrine System and Complex Immunologic System director · Interim pre-clerkship curriculum co-director
Sonam Kiwalkar
MD, FACP, MEHP · Endocrine System and Complex Immunologic System director · Interim pre-clerkship curriculum co-director
envelope icon
Table of Contents

Case study 1: Maribell

Tap the arrow to view the case.
Maribell, a 72-year-old woman, is evaluated for a 3-month history of abdominal and back pain and 4-month history of an increasingly rounded face.
On physical examination, vital signs are normal. BMI is 29. Bilateral lacrimal and parotid glands are enlarged. Laboratory evaluation shows a hemoglobin A1c  value of 5.4%, an alkaline phosphatase  level of 255 U/L, and an estimated glomerular filtration rate  of 59 mL/min/1.73 m2 (same as 1 year ago).
An abdominal CT scan shows periaortitis with a retroperitoneal mass that extends bilaterally and encircles both ureters without hydronephrosis. Needle biopsy of the mass reveals dense fibrous tissue in a storiform pattern, interspersed with an inflammatory infiltrate, including increased numbers of IgG4-positive plasmablasts. Serum IgG4 levels are not elevated.

In addition to prednisone, which of the following is the most appropriate treatment for Maribell?

    1. Cevimeline

Educational objective

Treat IgG4-related disease.

 

Key point

IgG4-related disease is treated with glucocorticoids and/or rituximab; rituximab monotherapy is appropriate when glucocorticoids are contraindicated.

 

Explanation

  • The correct answer is rituximab (Option C). Infiltrative involvement of the parotid and lacrimal glands with retroperitoneal fibrosis and periaortitis is characteristic of IgG4-related disease, confirmed by IgG4-positive plasmablasts on biopsy. Elevated alkaline phosphatase suggests biliary involvement. Normal serum IgG4 levels do not exclude the diagnosis. First-line therapy typically includes high-dose glucocorticoids, but rituximab is effective as monotherapy and is preferred when glucocorticoids pose excess risk.

  • Cevimeline (Option A) treats sicca symptoms in Sjögren syndrome but does not treat IgG4-related disease.

  • Methotrexate (Option B) has limited evidence in IgG4-related disease and is not first-line. 

  • Surgical debridement (Option D) is reserved for complications such as obstruction or vascular compromise, which are not present here.

IgG4‐related disease: review of the histopathologic features, differential diagnosis, and therapeutic approach​ APMIS, 2018.

Case study 2: Aslan

Tap the arrow to view the case.
Aslan, a 27-year-old man, comes to the office due to 6 days of eye redness and pain in both eyes. Medical history is significant for recurrent painful oral ulcers and ankylosing spondylitis. He currently takes aspirin and sulfasalazine. The patient is in a monogamous relationship but is unsure sure if his partner is monogamous. The patient immigrated from Turkey when he was a child.
Temperature is 36.5°C (97.7°F), pulse is 98/min, respirations are 14/min, and blood pressure is 120/70 mmHg. Physical examination shows warm and tender nodules over bilateral shins as well as his left ankle, as shown in the following image.
On ophthalmological examination, decreased visual acuity, conjunctival redness, and hypopyon are noted bilaterally.

Genital exam reveals an incipient genital ulceration over the scrotal raphe.

Laboratory studies show elevated erythrocyte sedimentation rate.

This patient most likely has which of the following conditions? 

    1. Primary syphilis
    2. Reactive arthritis
    3. Aphthous stomatitis
    4. Behcet disease
    5. Ankylosing spondylitis relapse

Rationale

  • This patient’s anterior uveitis (decreased visual acuity, conjunctival redness, hypopyon), recurrent painful aphthous ulcers, genital ulceration, and erythema nodosum are characteristic of Behçet disease. The disease is a multisystem vasculitis involving small, medium, and large vessels in both the arterial and venous circulation.
    • The etiology is unknown but is associated with HLA-B51 and may be triggered by infectious exposures. Diagnosis is clinical and relies on history and exam, with hallmark features including recurrent oral ulcers, genital ulcers, uveitis, and erythema nodosum; pathergy may also be present. Additional involvement can include the CNS, lungs, GI tract, and musculoskeletal system.
    • Flares typically last 1–4 weeks, and untreated disease can lead to permanent vision loss. Treatment includes anti-inflammatory therapy, systemic glucocorticoids, and TNF inhibitors for severe or refractory disease.
  • Herpes simplex virus (HSV) infection can cause oral or genital ulcers but does not produce recurrent multisystem involvement (uveitis, erythema nodosum, or pathergy).
  • Syphilis may cause mucocutaneous lesions or systemic signs but rarely causes recurrent oral ulcers, genital ulcers, and anterior uveitis together.
  • Reactive arthritis usually follows a GI or GU infection and is associated with conjunctivitis, urethritis, and asymmetric arthritis.

Image credits

Unless otherwise noted, images are from Adobe Stock.