Recommended Evaluation and Treatment
For a 10-year-old male with rash on feet and scrotum, perform a focused examination looking for palpable purpura (suggesting IgA vasculitis/Henoch-Schönlein purpura), psoriatic plaques, or eczematous changes, and if psoriasis is confirmed in the genital region, initiate tacrolimus 0.1% ointment as first-line therapy 1.
Diagnostic Approach
The combination of foot and scrotal involvement in a pediatric patient requires consideration of three primary differential diagnoses:
Key Clinical Features to Identify:
IgA Vasculitis (Henoch-Schönlein Purpura):
- Look for palpable purpura on lower extremities and feet
- Check for joint pain/swelling, abdominal pain, or hematuria
- Scrotal involvement presents as acute swelling, redness, and tenderness 2
- This is a systemic vasculitis requiring prompt recognition to avoid complications
- More common in children than adults, though scrotal involvement is rare 3
Psoriasis:
- Examine for well-demarcated erythematous plaques with silvery scale on feet
- Genital psoriasis often appears as smooth, red plaques without typical scaling
- Check scalp, elbows, knees for additional lesions
- Inverse/genital psoriasis is common in pediatric patients 1
Contact/Atopic Dermatitis:
- Look for poorly demarcated, eczematous, pruritic patches
- History of atopy or exposure to irritants
- Scrotal dermatitis can be easily mistaken for fungal infection 4
Treatment Algorithm
If Psoriasis is Diagnosed:
For genital/scrotal involvement:
- Tacrolimus 0.1% ointment is the preferred first-line therapy for pediatric genital psoriasis 1
- Evidence shows clearance within 2-3 weeks in pediatric patients 1
- Topical calcineurin inhibitors are specifically recommended over corticosteroids for face and genital regions to avoid skin atrophy and HPA axis suppression
For foot involvement:
- Combine high-potency topical corticosteroid with calcipotriene/calcipotriol for trunk and extremities 1
- Apply both medications once daily or mixed together twice daily for initial 2 weeks
- Transition to weekend corticosteroid application with weekday vitamin D analogue for maintenance
If IgA Vasculitis is Suspected:
- Urgent evaluation required due to potential systemic complications
- Check urinalysis for hematuria/proteinuria (renal involvement)
- Scrotal ultrasound if testicular pain or swelling present 2, 3
- Supportive care with NSAIDs for joint pain
- Corticosteroids for severe abdominal or renal involvement
If Contact/Atopic Dermatitis:
- Mid-potency topical corticosteroids for feet
- Low-potency corticosteroids or tacrolimus for scrotal area
- Identify and eliminate irritant exposures
Critical Pitfalls to Avoid
Do not use high-potency corticosteroids on genital skin in children due to increased absorption and risk of HPA axis suppression, skin atrophy, and striae 1. The genital area has thinner skin with higher absorption rates.
Do not dismiss scrotal involvement as simple fungal infection without proper examination—this can delay diagnosis of systemic conditions like IgA vasculitis or Crohn's disease 5, 4.
Monitor for systemic symptoms including abdominal pain, joint pain, or urinary changes that would indicate IgA vasculitis requiring more aggressive management 2.
For psoriasis specifically, tacrolimus 0.1% ointment has demonstrated clearance of penile psoriasis in a 10-year-old boy within 3 weeks 1, making it the evidence-based choice for this age and location. The strength of recommendation is C with level II-III evidence, but it represents the best available data for this specific clinical scenario.