What is the most likely diagnosis and recommended initial treatment for an 18‑year‑old female with a non‑pruritic erythematous rash on the cheeks, ears, and dorsal hands, progressive fever, fatigue, headaches, myalgias, constipation, and difficulty swallowing solids and liquids?

Most Likely Diagnosis: Dermatomyositis

This 18-year-old female most likely has dermatomyositis (DM), and should be started immediately on high-dose corticosteroids (prednisone 1 mg/kg/day or equivalent) as initial treatment.

Clinical Reasoning

The constellation of findings strongly points to dermatomyositis:

• Pathognomonic skin findings: Non-pruritic rash on cheeks, ears, and dorsal hands (likely Gottron's papules/sign and heliotrope rash)
• Systemic muscle involvement: Progressive myalgias, fatigue, and weakness
• Esophageal dysmotility: Difficulty swallowing both solids and liquids indicates smooth muscle involvement, a characteristic feature of inflammatory myopathies
• Constitutional symptoms: Fever, fatigue, headaches over 4 months

The dysphagia affecting both solids AND liquids is particularly telling—this pattern suggests esophageal smooth muscle dysfunction rather than mechanical obstruction, which is classic for dermatomyositis.

Classification and Diagnosis

According to the 2017 EULAR/ACR classification criteria for idiopathic inflammatory myopathies 1:

• For patients with pathognomonic skin rashes of DM, classification can be made without muscle biopsy
• A probability ≥55% (score ≥5.5) classifies as "probable IIM"
• A probability ≥90% (score ≥7.5 without biopsy) classifies as "definite IIM"
• The classification tree distinguishes juvenile DM (onset <18 years) from adult DM (onset ≥18 years)

This patient, at exactly 18 years old with characteristic rash and muscle symptoms, would likely meet criteria for dermatomyositis classification.

Initial Treatment Approach

Immediate corticosteroid therapy is the cornerstone of initial treatment:

• Prednisone 1 mg/kg/day (typically 60-80 mg daily for adults) is standard first-line therapy
• Continue high-dose therapy until clinical improvement and normalization of muscle enzymes (typically 4-6 weeks)
• Then taper gradually over months based on clinical response

Concurrent Workup Required

While initiating treatment, obtain:

• Muscle enzymes: CK, aldolase, AST, ALT, LDH
• Myositis-specific antibodies: Anti-Jo-1, anti-Mi-2, anti-TIF1-gamma, anti-MDA5
• EMG/NCS: To confirm myopathic pattern
• MRI of proximal muscles: Shows characteristic edema pattern
• Malignancy screening: DM in adults has 15-25% association with underlying malignancy (age-appropriate cancer screening)

Critical Pitfalls to Avoid

1. Don't delay treatment waiting for biopsy confirmation when skin findings are pathognomonic—the 2017 criteria specifically allow classification without biopsy in such cases 1

2. Don't miss the dysphagia: This requires specific attention as aspiration risk is significant. Consider:

   • Speech/swallow evaluation
   • Modified barium swallow study
   • Aspiration precautions

3. Don't forget steroid-sparing agents: Many patients will require addition of methotrexate, azathioprine, or mycophenolate mofetil within weeks to months for long-term control and steroid-sparing

4. Screen for malignancy: Particularly important in adult-onset DM (this patient is at the threshold age)

Why Not Other Diagnoses?

The research evidence about facial erythermalgia 2, 3 describes isolated facial burning and erythema responsive to cooling—this doesn't fit our patient who has systemic symptoms, myalgias, dysphagia, and hand involvement. The other guidelines 4, 5, 6, 7 address unrelated conditions (pulmonary embolism, lymphoma, stroke, leukemia) and are not applicable to this clinical presentation.