Diagnosis and Management of Adult with Rashes on Palms, Soles, and Tongue
This presentation demands immediate empiric doxycycline therapy for presumed Rocky Mountain Spotted Fever (RMSF) until proven otherwise, as delay in treatment significantly increases mortality from 5-10% to potentially fatal outcomes. 1, 2
Immediate Life-Threatening Diagnoses to Rule Out
The combination of palmar, plantar, and oral mucosal involvement in an adult creates a narrow but critical differential that prioritizes infectious etiologies with high mortality:
Rocky Mountain Spotted Fever (RMSF)
- Start doxycycline immediately without waiting for confirmatory testing or the classic triad of fever, rash, and tick exposure—only a minority present with all three initially. 1, 2
- The rash typically appears 2-4 days after fever onset as small blanching pink macules on ankles, wrists, or forearms that evolve to maculopapular lesions with central petechiae. 1, 3
- Petechial involvement of palms and soles indicates advanced disease and is associated with severe illness. 3, 2
- Up to 20% of RMSF cases never develop a rash, and absence of rash is associated with increased mortality. 1, 3
- Tick exposure history is present in only 60% of cases, so absence does not exclude diagnosis. 2
- 50% of deaths occur within 9 days of illness onset. 2
Meningococcemia
- Add ceftriaxone if meningococcemia cannot be excluded based on clinical presentation. 2
- Presents with petechial or purpuric rash that can rapidly progress to purpura fulminans alongside high fever, severe headache, and altered mental status. 3, 2
- Progresses more rapidly than RMSF. 2
- Up to 50% of early cases lack rash. 2
Secondary Syphilis
- Causes maculopapular rash involving palms and soles with oral mucous patches ("mucous patches" on tongue). 1, 3
- Obtain RPR/VDRL and treponemal-specific testing. 4
- Less acute presentation than RMSF or meningococcemia but requires identification. 3
Secondary Infectious Considerations
Ehrlichiosis (Ehrlichia chaffeensis)
- Rash occurs in approximately 30% of adults and 60% of children, with variable pattern that may involve palms and soles. 1
- Appears a median of 5 days after illness onset with fever, headache, malaise, and myalgia. 1
- 3% case-fatality rate. 1, 5
Bacterial Endocarditis
- Can cause petechiae on palms and soles in patients with cardiac risk factors. 3, 2
- Obtain blood cultures before antibiotics if possible, but do not delay treatment. 2
Kawasaki Disease
- Primarily affects children but can mimic RMSF in pediatric patients. 1
- Characterized by fever ≥5 days, red swollen tongue (strawberry tongue), cervical lymphadenopathy, swollen red skin on palms/soles, polymorphous rash, and irritability. 1
- Coronary artery aneurysm is a lethal complication. 1
Non-Infectious Differential Diagnoses
Hand-Foot-and-Mouth Disease (HFMD)
- Typically self-limited viral syndrome marked by fever, oral ulcers, and skin manifestations affecting palms, soles, and buttocks. 6
- Symptoms usually last less than 1 week. 6
- Peaks spring to fall. 2
- More common in children but can occur in adults. 6
Scabies
- Can involve palms in older children and adults if left untreated for long periods, particularly in hot tropical climates. 7
- Intensely pruritic with characteristic distribution in interdigital web spaces, flexor wrists, axillae, waist, buttocks, and genitalia. 7
Drug-Induced Hypersensitivity
- Drug reactions can cause petechial rash on palms and soles. 3
- Chemotherapy-induced hand-foot syndrome causes redness, marked discomfort, swelling, and tingling in palms, occurring in 6-60% of patients on capecitabine, 5-FU, doxorubicin, or multikinase inhibitors. 5
Diagnostic Algorithm
Step 1: Assess for systemic toxicity requiring immediate hospitalization
- Fever, tachycardia, confusion, hypotension, altered mental status, or rapidly progressive rash. 2
- Generalized petechiae or purpuric rash. 2
Step 2: Obtain focused history
- Recent outdoor activities in grassy/wooded areas (RMSF peaks April-September). 2
- Tick exposure (present in only 60% of RMSF cases). 2
- Recent medications or chemotherapy. 5
- Sexual history for secondary syphilis. 4
- Cardiac risk factors for endocarditis. 2
Step 3: Examine rash characteristics
- Petechial vs. maculopapular vs. vesicular. 1, 3
- Blanching vs. non-blanching. 3
- Oral involvement: mucous patches (syphilis), ulcers (HFMD), strawberry tongue (Kawasaki). 1, 6
Step 4: Obtain essential laboratory studies
- CBC with differential (thrombocytopenia, leukopenia, bandemia). 1, 2
- Comprehensive metabolic panel (hyponatremia, hepatic transaminase elevations). 1, 2
- Blood cultures before antibiotics if possible. 2
- RPR/VDRL for syphilis. 4
- Peripheral blood smear. 2
Step 5: Initiate empiric treatment
- Doxycycline immediately if RMSF cannot be excluded, even in children <8 years old. 2, 5
- Add ceftriaxone if meningococcemia cannot be excluded. 2
Critical Pitfalls to Avoid
- Do not wait for the classic triad of fever, rash, and tick bite in RMSF—it is present in only a minority of patients at initial presentation. 3, 2, 5
- Absence of rash does not exclude serious disease: up to 20% of RMSF cases and 50% of early meningococcal cases lack rash. 3, 2
- Rash on palms and soles is not pathognomonic for any single condition—consider RMSF, meningococcemia, secondary syphilis, endocarditis, and drug reactions. 3, 2
- In darker-skinned patients, petechial rashes may be difficult to recognize, increasing risk of delayed diagnosis. 3
- Do not delay treatment for laboratory confirmation in suspected RMSF or meningococcemia. 2
Treatment Approach
For suspected RMSF:
- Doxycycline 100 mg PO/IV twice daily for adults. 2
- Continue for at least 3 days after fever subsides and until evidence of clinical improvement, typically 5-7 days minimum. 1
For suspected meningococcemia:
- Ceftriaxone 2 g IV every 12-24 hours. 2
For confirmed secondary syphilis:
- Benzathine penicillin G 2.4 million units IM single dose. 4
For HFMD: