Confusable diagnoses · PANCE / PANRE

Cellulitis vs Erysipelas

Written & clinically reviewed by Ryan Busch, PA-C · Updated August 2026 · Report an error

Cellulitis and Erysipelas are easy to mix up on the boards. Here's a side-by-side comparison — presentation, workup, imaging, and first-line treatment — drawn from our full outlines.

Cellulitis vs Erysipelas at a glance

  • Cellulitis: Acute bacterial infection of the dermis and subcutaneous tissue, most often caused by beta-hemolytic streptococci or Staphylococcus aureus.
  • Erysipelas: Superficial cellulitis with prominent lymphatic involvement, sharply demarcated borders, and a classic 'peau d'orange' appearance — almost always streptococcal.

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Question 1Infectious DiseaseMedium
A 58-year-old woman has had her fourth episode of left lower-leg cellulitis in the past 2 years. Each episode presented with warmth, erythema, and tenderness of the calf that responded to oral cephalexin. She has chronic interdigital tinea pedis. Examination today shows resolving erythema of the distal leg. Which of the following complications is she most likely to develop as a result of these recurrent infections?
  • APersistent lymphedema
  • BInfective endocarditis
  • CNecrotizing fasciitis
  • DVenous insufficiency
Reveal answer & full explanation
Correct answer: A — Persistent lymphedema
  • APersistent lymphedema✓
  • BInfective endocarditis
  • CNecrotizing fasciitis
  • DVenous insufficiency

Why Persistent lymphedema is correct

  • Recurrent cellulitis damages dermal lymphatic channels, and each episode of streptococcal infection further impairs lymphatic drainage, producing progressive, often non-pitting chronic lymphedema.
  • This sets up a vicious cycle: lymphedema is itself a major risk factor for cellulitis, so recurrent infection and worsening edema reinforce each other, and her interdigital tinea pedis provides a recurring portal of entry.
  • With repeated episodes the skin can become fibrotic and verrucous (elephantiasis nostras verrucosa); eradicating portals of entry such as tinea pedis and using prophylactic penicillin in patients with frequent recurrences reduce further episodes.

Why the others are wrong

  • Infective endocarditis - a recognized complication of Staphylococcus aureus bacteremia, but this patient has non-purulent, locally limited, antibiotic-responsive cellulitis without bacteremia, so endocarditis is far less likely than progressive lymphedema.
  • Necrotizing fasciitis - a fulminant deep soft-tissue infection marked by pain out of proportion, bullae, crepitus, and systemic toxicity; it is an acute surgical emergency, not a chronic consequence of repeated, antibiotic-responsive episodes of ordinary cellulitis.
  • Venous insufficiency - a predisposing condition for leg cellulitis rather than a consequence of it; recurrent streptococcal cellulitis scars the dermal lymphatics, not the venous valves, so repeated episodes lead to lymphedema rather than venous hypertension.
Question 2Infectious DiseaseMedium
A 71-year-old woman with chronic lower-extremity lymphedema presents with one day of fever, chills, and a painful right leg. She has interdigital scaling and fissuring between her toes. On exam, temperature is 38.7°C and there is a fiery-red, warm, tender plaque on the right shin with a raised, sharply demarcated border that can be traced with a fingertip. Tender inguinal lymphadenopathy and a streak of erythema tracking up the medial thigh are noted. A clinical diagnosis of erysipelas is made. Which of the following best explains this patient's findings?
  • ABacterial proliferation within the deep dermis and subcutaneous fat
  • BStreptococcal spread through the superficial dermal lymphatics
  • CPolymicrobial invasion of the deep fascial plane with thrombosis
  • DToxin-mediated cleavage of the superficial epidermal granular layer
Reveal answer & full explanation
Correct answer: B — Streptococcal spread through the superficial dermal lymphatics
  • ABacterial proliferation within the deep dermis and subcutaneous fat
  • BStreptococcal spread through the superficial dermal lymphatics✓
  • CPolymicrobial invasion of the deep fascial plane with thrombosis
  • DToxin-mediated cleavage of the superficial epidermal granular layer

Why Streptococcal spread through the superficial dermal lymphatics is correct

  • Erysipelas is a beta-hemolytic streptococcal (usually group A, S. pyogenes) infection of the upper dermis and superficial lymphatics.
  • Organisms enter through a skin breach (here, fissured tinea pedis) and propagate within superficial dermal lymphatics; M protein, hyaluronidase, and streptolysins drive brisk inflammation.
  • This superficial lymphatic involvement produces the hallmark raised, sharply demarcated, traceable border plus lymphangitic streaking and regional lymphadenopathy that are described.

Why the others are wrong

  • Polymicrobial invasion of the deep fascial plane with thrombosis describes necrotizing fasciitis; expect pain out of proportion, rapid expansion, bullae, crepitus, and systemic toxicity rather than a sharply bordered superficial plaque.
  • Bacterial proliferation within the deep dermis and subcutaneous fat is the mechanism of cellulitis, which involves deeper tissue and characteristically has indistinct, poorly demarcated borders rather than the raised clear edge of erysipelas.
  • Toxin-mediated cleavage of the superficial epidermal granular layer describes staphylococcal scalded skin syndrome (exfoliative toxin splitting desmoglein-1), producing diffuse desquamation and a positive Nikolsky sign rather than a localized erythematous lymphangitic plaque.
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Side-by-side comparison

FeatureCellulitisErysipelas
At a glanceAcute bacterial infection of the dermis and subcutaneous tissue, most often caused by beta-hemolytic streptococci or Staphylococcus aureus.Superficial cellulitis with prominent lymphatic involvement, sharply demarcated borders, and a classic 'peau d'orange' appearance — almost always streptococcal.
Classic presentationUnilateral lower-leg cellulitis is extremely common; bilateral lower-leg 'cellulitis' is almost never cellulitis — consider stasis dermatitis, lipodermatosclerosis, or contact dermatitis.; Localized warmth, erythema, edema, tenderness — usually a single extremity; Spreading borders without sharp demarcation; Fever, chills, malaise in…A sharply demarcated, raised, fiery red facial or leg plaque with a clear edge ('the lesion you can trace') and a high fever — classic erysipelas.; Abrupt onset of fever, chills, malaise — often precedes rash by hours; Localized burning pain and tenderness; Bright red, hot, swollen plaque with sharply raised border; Classic…
Workup / key labsClinical diagnosis. IDSA stratifies into mild, moderate, severe and purulent vs non-purulent for treatment selection.; CBC, BMP, lactate if systemic toxicity; Blood cultures only if severe sepsis, immunocompromise, water exposure, animal/human bites, or unusual organism suspected; Wound culture if purulent drainage or abscess (incise…Clinical: sharply demarcated, raised, brightly erythematous, warm, tender plaque with systemic symptoms.; Clinical diagnosis — labs not routinely required; CBC, CRP, ESR if hospitalized or severe; Blood cultures yield in ~5% — only if systemic toxicity, immunocompromise, atypical presentation; ASO/anti-DNase B may support recent…
ImagingBedside ultrasound to differentiate cellulitis (cobblestoning) from abscess (anechoic collection); Plain films for foreign body, soft tissue gas (necrotizing infection), or osteomyelitis; CT/MRI if necrotizing fasciitis suspected (but do NOT delay surgical consultation for imaging)Not required for typical presentations; Ultrasound to exclude abscess if purulence suspected
First-line treatmentNon-purulent cellulitis (likely beta-hemolytic strep):; • Mild (no systemic signs), outpatient: oral beta-lactam — cephalexin 500 mg PO QID, dicloxacillin 500 mg PO QID, or penicillin VK; • Moderate (systemic signs of infection: T >38°C, HR >90, RR >24, or WBC >12,000 or <4,000): IV cefazolin, ceftriaxone, or penicillin; • Severe…Penicillin remains drug of choice — narrow spectrum, predictable streptococcal coverage:; • Oral: penicillin VK 500 mg PO QID or amoxicillin 500 mg PO TID × 5-10 days; • IV: penicillin G 2-4 million units IV q4-6h, or ceftriaxone 1 g IV daily; Penicillin allergy: cephalexin or cefazolin if the prior reaction was not immediate-type or…

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Full outlines

Cellulitis Erysipelas All 514 diagnoses

Educational use only. This outline is a study aid for PA students and is not medical advice or a substitute for clinical judgment. FirstPassPA is an independent study tool and is not affiliated with, endorsed by, or sponsored by NCCPA or PAEA. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants; End of Rotation™ is a program of the Physician Assistant Education Association.