What is the next step in managing a maculopapular rash on the belly and sternum in a patient who has not responded to antifungal treatment?

Management of Maculopapular Rash Unresponsive to Antifungal Therapy

Stop the antifungal immediately and perform a skin biopsy to establish the correct diagnosis, as failure to respond to antifungal treatment indicates this is not a fungal infection. 1

Immediate Diagnostic Reassessment

The lack of response to antifungal therapy definitively rules out superficial fungal infection as the primary diagnosis. 2 You must now systematically evaluate for alternative etiologies:

Critical Red Flags to Assess Immediately

• Fever with systemic toxicity: Check temperature, blood pressure, and mental status—if fever >38.5°C with hypotension or altered mental status, this could be meningococcemia or Rocky Mountain Spotted Fever requiring immediate empiric doxycycline 100mg IV BID. 1

• Mucosal involvement: Examine oral mucosa, conjunctiva, and genitals—any ulceration or erosion with skin detachment indicates Stevens-Johnson syndrome/TEN requiring immediate hospitalization. 1

• Rash evolution: Document if blanching pink macules are evolving to maculopapular lesions with central petechiae, which is classic for RMSF. 1

Essential Physical Examination Details

• Distribution pattern: Centripetal spread (trunk to extremities) suggests viral exanthem or drug reaction; involvement of palms and soles points toward secondary syphilis or RMSF. 1

• Morphology characteristics: Determine if lesions are truly maculopapular versus petechial/purpuric (non-blanching suggests vasculitis). 3

Diagnostic Algorithm Based on Clinical Presentation

If Patient is Febrile and Systemically Ill

Start empiric doxycycline 100mg PO/IV BID immediately without waiting for confirmatory testing if RMSF cannot be excluded, as mortality risk outweighs treatment delay. 1 Add ceftriaxone 2g IV if meningococcemia is possible. 1

Obtain before antibiotics if possible: 1

• CBC with differential
• Comprehensive metabolic panel
• Blood cultures

If Patient is Afebrile Without Systemic Symptoms

The most likely diagnoses are:

Drug reaction (most common): 4

• Review all medications started within the past 2-4 weeks, including over-the-counter products
• Discontinue the most likely offending agent
• For grade 1-2 rash (<30% body surface area): Apply topical corticosteroid (clobetasol propionate for body, hydrocortisone 2.5% for face) twice daily plus oral antihistamine (cetirizine 10mg daily). 5
• For grade 3 rash (>30% body surface area): Hold the offending medication, start prednisone 0.5-1 mg/kg/day, and obtain dermatology consultation. 5

Allergic contact dermatitis: 6

• If rash is recurrent and localized to areas of potential allergen exposure (clothing elastic, jewelry contact areas on trunk)
• Escalate to medium-potency topical steroid (triamcinolone 0.1%) rather than continuing ineffective treatment. 6
• Refer for patch testing to identify causative allergen. 6

Viral exanthem: 4

• Consider if recent viral prodrome or exposure
• Management is supportive with antihistamines for pruritus

Skin Biopsy Indications

Perform punch biopsy if: 1

• Diagnosis remains unclear after initial assessment
• Rash is progressive despite empiric treatment
• Vasculitis is suspected (purpuric/petechial component)
• Immunotherapy-related dermatitis is possible (if patient on checkpoint inhibitors). 5

Critical Management Pitfalls to Avoid

• Never continue ineffective antifungal therapy while "waiting to see if it works"—this delays correct diagnosis and treatment. 6, 2

• Never dismiss RMSF based on absence of reported tick bite—only a minority of patients recall tick exposure at initial presentation. 1

• Never assume this is "just eczema" without investigating for contact dermatitis or drug reaction, as allergen avoidance is the only definitive treatment. 6

• Never use topical antifungals for non-fungal rashes—they provide no benefit and may contain preservatives that worsen contact dermatitis. 2

When to Escalate Care

Obtain urgent dermatology consultation if: 5

• Rash progresses to >30% body surface area
• Systemic symptoms develop (fever, lymphadenopathy, arthralgias)
• Mucosal involvement appears
• No improvement after 2 weeks of appropriate topical corticosteroid treatment

Hospitalize immediately if: 1

• Fever with systemic toxicity
• Any mucosal involvement with skin detachment
• Rapidly progressive rash with hemodynamic instability