What are other causes of a generalized or patchy rash accompanied by scrotal edema?

Other Causes of Rash with Scrotal Edema

When a patient presents with both generalized or patchy rash and scrotal edema, the most critical diagnoses to consider are lymphatic filariasis, IgA vasculitis (Henoch-Schönlein purpura), and Crohn's disease with metastatic cutaneous involvement.

Life-Threatening Causes Requiring Immediate Intervention

Fournier's Gangrene (Necrotizing Fasciitis)

• Beta-hemolytic streptococcal cellulitis of the scrotum can rapidly progress to skin gangrene if the compartment between Colles' and Buck's fascia is not immediately decompressed with linear incisions 1
• Fluid accumulates rapidly in this closed space, producing intense scrotal swelling and subsequent devascularization of scrotal and penile skin 1
• Immediate treatment with penicillin is essential, and radical debridement of necrotic tissue plus a wide margin of adjacent inflamed skin must be undertaken if gangrene develops 1
• Diabetic patients with acute scrotal swelling require immediate imaging and surgical consultation, as diabetes increases risk of rapid progression to life-threatening Fournier's gangrene 2

Infectious/Parasitic Causes

Lymphatic Filariasis (Wuchereria bancrofti and Brugia species)

• Acute fever with localized skin inflammation, lymphadenitis, and lymphangitis is followed by chronic lymphedema and scrotal edema/hydrocele 3
• The condition is endemic in parts of Africa, West Pacific, Caribbean, South America, India, and Southeast Asia 3
• Diagnosis requires serology and nocturnal blood microscopy (10 pm to 2 am in 4x citrated blood bottles, 20 ml total volume, not refrigerated) 3
• Treatment involves diethylcarbamazine (DEC) 6 mg/kg in 3 divided doses for 14 days plus doxycycline 200 mg daily for 6 weeks 3

Onchocerciasis (River Blindness)

• Presents with mild to intense pruritus and limb swelling in travelers, with nodules appearing on bony prominences, head, and trunk 3
• Diagnosis through microscopic visualization of microfilariae following incubation of skin snips in normal saline or slit lamp examination 3
• Treatment requires doxycycline 200 mg once daily for 6 weeks plus ivermectin 200 μg/kg monthly for 3 months 3

Strongyloides stercoralis (Larva Currens)

• Presents as an itchy, linear, urticarial rash that moves 5-10 cm per hour, occurring most commonly around the trunk, upper legs, and buttocks 3
• Associated with subcutaneous larval migration in S. stercoralis infection 3

Inflammatory/Autoimmune Causes

IgA Vasculitis (Henoch-Schönlein Purpura)

• Scrotal involvement occurs in approximately 14.5% of male patients with IgA vasculitis and is associated with more severe disease activity 4
• Patients present with scrotal pain, swelling, and rash (44%), scrotal pain and swelling alone (35%), or isolated scrotal swelling (6%) 4
• Widespread purpura, local edema, penile involvement (5.9% of cases), and hematuria are significantly more common in patients with scrotal involvement 4
• Pediatric vasculitis activity score (PVAS) and CRP-to-albumin ratio (CAR) are significantly higher in patients with scrotal involvement and may help predict this complication 4

Metastatic Crohn's Disease

• Penile and scrotal swelling can occur as an extraintestinal manifestation of Crohn's disease, and in 88% of cases, cutaneous symptoms precede the formal diagnosis of Crohn's disease 5
• Two-thirds of patients with genital metastatic Crohn's disease have no gastrointestinal symptoms at the time of presentation 5
• An evaluation for Crohn's disease is necessary in all patients presenting with unexplained genital swelling 5
• Treatment of the underlying Crohn's disease with systemic medications (average 3.4 medications per patient) is most effective for managing genital involvement 5

Dermatologic Causes

Scrotal Dermatitis

• Scrotal dermatitis is a very common condition that is easily mistaken for fungal infections and has been overlooked as a separate disease entity 6
• The condition has distinct etiological factors and pathogenesis compared to contact dermatitis occurring elsewhere 6
• Narrow-band UVB phototherapy can be used for management of scrotal dermatitis 6

Diagnostic Approach

Initial Assessment

• Ultrasound with Doppler is the first-line imaging modality for evaluating scrotal edema, with high sensitivity and specificity for distinguishing between various etiologies 7
• Both grayscale and color Doppler ultrasound should be performed to assess testicular perfusion and identify potential causes 7
• Always exclude testicular torsion first, as delay beyond 6-8 hours significantly increases risk of testicular loss 7, 2

Key Clinical Features to Assess

• Travel history to endemic areas for filariasis (Africa, West Pacific, Caribbean, South America, India, Southeast Asia) 3
• Presence of purpuric rash, particularly in children, suggesting IgA vasculitis 4
• Gastrointestinal symptoms or history suggesting Crohn's disease 5
• Acute onset with fever and rapidly progressive swelling suggesting necrotizing infection 1
• Pattern and migration of rash (linear and moving suggests larva currens) 3

Critical Pitfalls to Avoid

• False-negative Doppler evaluations can occur in partial torsion or spontaneous detorsion, so proceed to surgery if clinical suspicion remains high 7, 2
• Early presentation may not show all classic symptoms, potentially leading to missed diagnosis of serious conditions 7
• Do not dismiss scrotal edema as simple dermatitis without considering systemic causes like Crohn's disease or vasculitis 6, 5
• Failure to improve within 3 days of treatment requires reevaluation of both diagnosis and therapy 7
• Persistent swelling after completing antimicrobial therapy should prompt comprehensive evaluation for tumor, abscess, infarction, testicular cancer, or tuberculous/fungal infection 7