Dermatology MCQ - Inflammatory Dermatoses - Dermatomyositis management

A 48-year-old woman is diagnosed with dermatomyositis based on heliotrope rash, Gottron's papules, proximal muscle weakness, and a confirmatory muscle biopsy. She has failed to improve after an 8-week course of high-dose oral prednisone (1 mg/kg/day). What is the most appropriate next step in the management of her disease?

A. Add oral methotrexate or mycophenolate mofetil
B. Switch to an intravenous steroid pulse (methylprednisolone)
C. Initiate a prolonged steroid taper over 12 months
D. Refer for physical therapy alone
E. Begin a trial of dapsone

Correct Answer: A. Add oral methotrexate or mycophenolate mofetil

Explanation

The management of dermatomyositis (DM) follows a step-wise approach. High-dose corticosteroids are the first-line treatment for active myositis. However, many patients have an inadequate response, require unacceptably high maintenance doses, or develop significant side effects.

• Steroid-Sparing Immunosuppressive Agents: In a patient who has failed an adequate trial of high-dose corticosteroids, the standard next step is to add a steroid-sparing immunosuppressive agent. Methotrexate and mycophenolate mofetil are both considered first-line options for this role. They work slowly but allow for a reduction in the corticosteroid dose while providing long-term control of the disease.

Why other options are incorrect

• B. Switch to an intravenous steroid pulse (methylprednisolone): IV pulse steroids are typically reserved for the initial treatment of severe, life-threatening disease (e.g., with profound weakness, dysphagia, or respiratory involvement) or for acute flares. In a patient who has already failed 8 weeks of high-dose oral steroids, simply switching the route of administration is unlikely to be effective and does not address the need for long-term steroid-sparing therapy.

• C. Initiate a prolonged steroid taper over 12 months: A slow taper is the goal, but it is not possible in a patient who has not responded to the initial high dose. Continuing high-dose steroids for a prolonged period without an effective adjunctive agent exposes the patient to severe cumulative toxicity without adequate disease control.

• D. Refer for physical therapy alone: Physical therapy is a crucial adjunct to pharmacologic therapy to maintain range of motion and prevent contractures, but it is not a treatment for the underlying autoimmune inflammation and is insufficient as monotherapy for active disease.

• E. Begin a trial of dapsone: Dapsone may have a role in treating the skin manifestations of DM, particularly ulcerative lesions, but it has no efficacy for the underlying myositis and is not appropriate as the next step for managing refractory muscle disease.

Key Associations for Dermatomyositis Management

• First-Line Therapy: Systemic corticosteroids (e.g., prednisone 0.5-1 mg/kg/day) are the initial treatment for most patients with active muscle disease.

• Steroid-Sparing Agents (First-Line Add-On Therapy):

  • Methotrexate: Effective for both skin and muscle disease.

  • Mycophenolate Mofetil: Particularly effective for skin disease and increasingly used for myositis. It has a favorable side-effect profile.

  • Azathioprine: A classic steroid-sparing agent, though its onset of action is slower.

• Second-Line & Refractory Disease:

  • Intravenous Immunoglobulin (IVIG): Has robust evidence for efficacy in refractory DM for both skin and muscle. It is often used for rapidly progressive disease or when conventional immunosuppressants are contraindicated or ineffective.

  • Rituximab: An anti-CD20 monoclonal antibody used for severe, refractory disease.

  • Cyclosporine or Tacrolimus: Calcineurin inhibitors that can be effective, especially when there is associated interstitial lung disease.

• Cutaneous Disease Management: The skin disease can be refractory to systemic therapy. First-line skin-specific treatments include sun protection, topical corticosteroids, and topical calcineurin inhibitors. Hydroxychloroquine is often used as a first-line systemic agent for skin-predominant disease. Refractory skin disease may require methotrexate, mycophenolate, or IVIG.

• Associated Malignancy: All adults with a new diagnosis of DM require a comprehensive age- and risk-appropriate malignancy work-up, as there is a well-established association, particularly with anti-TIF1γ antibodies.