1. Basic Dermatology Curriculum
The Red Leg
Basic Dermatology Curriculum
Last updated June 16, 2011

2. Module Instructions
The following module contains a number of blue, underlined terms which are hyperlinked to the dermatology glossary, an illustrated guide to clinical dermatology and dermatopathology.
We encourage the learner to read all the hyperlinked information.

3. Goals and Objectives
The purpose of this module is to help medical students develop a clinical approach to the evaluation and initial management of patients presenting with an erythematous leg.
By completing this module, the learner will be able to:
Recognize common and life-threatening causes of an erythematous leg
List the various risk factors for the conditions presented in this module
Describe the initial treatment plans for each condition presented in this module
Determine when to refer patients presenting with a red leg to a dermatologist or other specialty

4. Case One
Mr. Roy Clarke

5. Case One: History
HPI: Mr. Clarke is a 55-year-old man who presents with 5 days of worsening right lower extremity pain and a red rash. He reports recent fevers and chills since he returned from a camping trip last week.
PMH: arthritis
Medications: occasional NSAIDs, multivitamin
Allergies: no known drug allergies
Family history: father with history of melanoma
Social history: lives in the city with his wife, two grown children
Health-related behaviors: no alcohol, tobacco or drug use
ROS: able to bear weight, no itching

6. Case One: Exam
Vital signs: T 100.4, HR 90, BP 120/70, RR 14, O2 sat 97% on RA
Skin: erythematous plaque with ill-defined borders over the right medial malleolus. Lesion is tender to palpation. With lymphatic streaking (not shown).
Tender, slightly enlarged right inguinal lymph nodes (not shown)
Laboratory data: Wbc 12,000 (75% neutrophils, 10% bands), Hct 44, Plts 335

7. Case One, Question 1 What is the most likely diagnosis?
Bacterial folliculitis
Cellulitis
Necrotizing fasciitis
Stasis dermatitis
Tinea corporis

8. Case One, Question 1 Answer: b What is the most likely diagnosis?
Bacterial folliculitis (Would expect pustules and papules centered on hair follicles. Without systemic signs of infection.)
Cellulitis
Necrotizing fasciitis (Would expect rapidly expanding rash, usually appears as a dusky, edematous, red plaque. In this setting, it is always appropriate to ask the question, “Could this be necrotizing fasciitis?”)
Stasis dermatitis (Although found in similar location, stasis dermatitis often presents with pruritus and scale, which may erode or crust. Without fever or elevated wbc.)
Tinea corporis (Would expect annular plaque with elevated border and central clearing. Painless, without fever or elevated wbc.)

9. Diagnosis: Cellulitis
Cellulitis is a very common infection occurring in up to 3% of people per year
Results from an infection of the dermis that often begins with a portal of entry such as a wound or fungal infection (e.g., tinea pedis)
Group A beta-hemolytic streptococci and Staphyloccocus aureus are the most common causal pathogens
Presents as a spreading erythematous, non-fluctuant tender plaque
More commonly found on the lower leg
Streaks of lymphangitis may spread from the area to the neighboring lymph glands

10. Erysipelas
Erysipelas is a superficial cellulitis with marked dermal lymphatic involvement (causing the skin to be edematous or raised)
Main pathogen is group A streptococcus
Usually affects the lower extremities and the face
Presents with pain, superficial erythema, and plaque-like edema with a sharply defined margin to normal tissue
Plaques may develop overlying blisters (bullae)
May be associated with a high white count (>20,000/mcL)
May be preceded by chills, fever, headache, vomiting, and joint pain

11. Example of Erysipelas
Large, shiny erythematous plaque with sharply demarcated borders located on the posterior leg

12. Mr. Clarke was diagnosed with cellulitis.
Back to Case One
Mr. Clarke was diagnosed with cellulitis.

13. Case One, Question 2 What is the next best step in management?
Apply topical antibiotics
Apply topical steroids, compression wraps, and encourage leg elevation
Begin antibiotics immediately with coverage for gram positive bacteria
Order an imaging study

14. Case One, Question 2 Answer: c
What is the next best step in management?
Apply topical antibiotics (not effective)
Apply topical steroids, compression wraps, and encourage leg elevation (this is the treatment for stasis dermatitis, not cellulitis)
Begin antibiotics immediately with coverage for gram positive bacteria
Order an imaging study (radiographic examination is not necessary for routine evaluation of patients with cellulitis)

15. Cellulitis: Treatment
It is important to recognize and treat cellulitis early as untreated cellulitis may lead to sepsis and death
May use the following guidelines for empiric antibiotic therapy:
For outpatients with nonpurulent cellulitis: empirically treat for β-hemolytic streptococci (group A streptococcus)
Some clinicians choose an agent that is also effective against S. aureus
For outpatients with purulent cellulitis (purulent drainage or exudate in the absence of a drainable abscess): empirically treat for community-associated MRSA
For unusual exposures: cover for additional bacterial species likely to be involved

16. Cellulitis: Treatment (cont.)
Monitor patients closely and revise therapy if there is a poor response to initial treatment
Elevation of the involved area
Treat tinea pedis if present
For hospitalized patients: empiric therapy for MRSA should be considered
Cultures from abscesses and other purulent skin and soft tissue infections (SSTIs) are recommended in patients treated with antibiotic therapy

17. Case Two
Mr. Anthony Bice

18. Case Two: History
HPI: Mr. Bice is a 66-year-old man who was admitted for an inguinal hernia repair. His surgery went well and he was recovering without complication until he was found to have an expanding red rash on his left thigh. The dermatology service was consulted for evaluation of the rash.
PMH: hypertension, diabetes mellitus type 2
Medications: lisinopril, insulin, oxycodone
Allergies: none
Family history: noncontributory
Social history: retired, lives with his wife
Health-related behaviors: reports no alcohol, tobacco, or drug use
ROS: febrile, fatigue, rash is painful

19. Case Two: Exam
Vital signs: T 101.1, HR 110, BP 90/50, RR 18, O2 sat 98%
General: ill-appearing gentleman lying in bed
Skin: ill-defined, anesthetic, large erythematous plaque with central patches of dusky blue discoloration; upon re- examination 60 minutes later, the redness had spread

20. Case Two, Question 1
Which of the following do you recommend for initial management?
Call an urgent surgery consult
Give IV fluids and antibiotics
Image with stat MRI
Obtain a deep skin biopsy
All of the above

21. Case Two, Question 1 Answer: e
Which of the following do you recommend for initial management?
Call an urgent surgery consult (The suspected diagnosis is a surgical emergency.)
Give IV fluids and antibiotics (Patients quickly become hemodynamically unstable.)
Image with stat MRI (To assess degree of soft tissue involvement. Appropriate, but do not delay surgical intervention.)
Obtain a deep skin biopsy (Helps confirm diagnosis.)
All of the above

22. Diagnosis: Necrotizing Fasciitis
Necrotizing fasciitis is a life-threatening infection of the fascia just above the muscle
Progresses rapidly over the course of hours and may follow surgery or trauma, or have no preceding visible lesion
Expanding dusky, edematous, red plaque with blue discoloration
May turn purple and blister
Anesthesia of the skin of the affected area is a characteristic finding
Caused by group A streptococcus, Staphylococcus aureus, or a variety of other organisms

23. Necrotizing Fasciitis: Treatment
Considered a medical/surgical emergency with up to a 20% fatality rate
If suspect necrotizing fasciitis, consult surgery immediately
Treatment includes widespread debridement and broad-spectrum systemic antibiotics
Poor prognostic factors include: delay in diagnosis, age > 50, diabetes, atherosclerosis, infection involving the trunk

24. Case Three
Ms. Janet Frasier

25. Case Three: History
HPI: Ms. Frasier is a 43-year-old woman with a recent diagnosis of gout who presents to her primary care provider with a diffuse rash on her lower extremities. The rash began 4 days after starting indomethacin for an acute gout attack.
PMH: gout, no hospitalizations or surgeries
Medications: indomethacin, zolpidem
Allergies: none
Social history: lives by herself in an apartment
Health-related behaviors: history of significant alcohol use, last drink 3 years ago. No tobacco or drug use.
ROS: no current fevers, sweats or chills

26. Case Three: Skin Exam Normal vital signs General: appears well in NAD
Skin exam: palpable hemorrhagic papules coalescing into plaques, bilateral and symmetric on lower extremities

27. Case Three, Question 1
Which of the following is the most likely cause of Ms. Frasier’s skin findings?
DIC secondary to sepsis
Leukocytoclastic vasculitis secondary to NSAID
Septic emboli with hemorrhage from undiagnosed bacterial endocarditis
Urticarial vasculitis

28. Case Three, Question 1 Answer: b
Which of the following is the most likely cause of Ms. Frasier’s skin findings?
DIC secondary to sepsis (Ms. Frasier’s history and exam are less concerning for sepsis. Skin lesions of DIC tend to occur on acral and distal sites, with a retiform (netlike) purpura.)
Leukocytoclastic vasculitis secondary to NSAID
Septic emboli with hemorrhage from undiagnosed bacterial endocarditis (Ms. Frasier has no known risk factors for endocarditis and lesions tend to occur on the distal extremities.)
Urticarial vasculitis (Presents with a different morphology, which is urticarial.)

29. Palpable Purpura
Palpable purpura results from inflammation of small cutaneous vessels, i.e. vasculitis
Vessel inflammation results in vessel wall damage and in extravasation of erythrocytes seen as purpura on the skin
Vasculitis may occur as a primary process or may be secondary to another underlying disease
Palpable purpura is the hallmark lesion of leukocytoclastic vasculitis (small vessel vasculitis)

30. Vasculitides According to Size of the Blood Vessels
Small vessel vasculitis (leukocytoclastic vasculitis)
Henoch-Schönlein purpura
Other:
Idiopathic
Malignancy-related
Rheumatologic
Infection
Medication
Urticarial vasculitis

31. Vasculitides According to Size of the Blood Vessels
Predominantly Mixed (Small + Medium)
ANCA associated vasculitides
Churg-Strauss syndrome
Microscopic polyangiitis
Wegener granulomatosis
Essential cryoglobulinemic vasculitis
Predominantly medium sized vessels
Polyarteritis nodosa
Predominantly large vessels
Giant cell arteritis
Takayasu arteritis

32. Clinical Evaluation of Vasculitis
The following laboratory tests may be used to evaluate patient with suspected vasculitis:
CBC with platelets
ESR (systemic vasculitides tend to have sedimentation rates > 50)
ANA (a positive antinuclear antibody test suggests the presence of an underlying connective tissue disorder)
ANCA (helps diagnose Wegener granulomatosis, microscopic polyarteritis, drug-induced vasculitis, and Churg-Strauss)
Complement (low serum complement levels may be present in mixed cryoglobulinemia, urticarial vasculitis and lupus)
Urinalysis (helps detect renal involvement)
Also consider ordering cryoglobulins, an HIV test, HBV and HCV serology, occult stool samples, an ASO titer and streptococcal throat culture

33. Diagnosis: Leukocytoclastic Vasculitis (LCV)
The primary care provider also suspects LCV secondary to medication hypersensitivity, but to make sure she has not missed any other causes of vasculitis she orders laboratory tests and refers the patient to a dermatologist
Ms. Frasier was recommended to stop the indomethacin

34. Case Four
Mrs. Belinda Strong

35. Case Four: History
HPI: Mrs. Strong is a 60-year-old woman who presents with a “rash” on her leg that has been present for 2 months. She reports no pain, but does experience mild pruritus.
PMH: diabetes (last hemoglobin A1c was 6.7), hypertension, obesity. No history of atopic dermatitis.
Medications: lisinopril, metoprolol, glyburide
Allergies: none
Family history: mother with diabetes and hypertension
Social history: lives with her husband in the city, four grown children, two grandchildren
Health-related behaviors: no tobacco, alcohol or drug use
ROS: no leg pain when walking or at rest

36. Case Four, Question 1
How would you describe these skin findings?

37. Case Four, Question 1
Large erythematous plaques with fine fissuring and scale as well as interspersed brown macular hyperpigmentation

38. Case Four, Question 2 What is the most likely diagnosis?
Atopic dermatitis
Bilateral cellulitis
Stasis dermatitis
Tinea corporis

39. Case Four, Question 2 Answer: c What is the most likely diagnosis?
Atopic dermatitis (adults with AD have a history of childhood AD and a different distribution of skin involvement)
Bilateral cellulitis (cellulitis occurs more acutely, presents with fever and pain, more erythema, well-demarcated and without pruritus or scale)
Stasis dermatitis
Tinea corporis (would expect sharply marginated, erythematous annular patches with central clearing)

40. Diagnosis: Stasis Dermatitis
Stasis dermatitis typically presents with erythema, scale, pruritus, erosions, exudate, and crust
Usually located in the lower third of the legs, superior to the medial malleolus
Can occur bilaterally or unilaterally
Lichenification may develop
Edema is often present, as well as varicose veins and hemosiderin deposits (pinpoint yellow-brown macules and papules)

41. More Examples of Stasis Dermatitis

42. More Examples of Stasis Dermatitis

43. Case Four, Question 3
Which of the following treatments do you recommend for Mrs. Strong ?
Leg elevation, compression therapy
Leg elevation, topical antibiotics
Leg elevation, topical corticosteroids, compression therapy
Topical corticosteroids

44. Case Four, Question 3 Answer: c
Which of the following treatments do you recommend for Mrs. Strong?
Leg elevation, compression therapy
Leg elevation, topical antibiotics
Leg elevation, topical corticosteroids, compression therapy
Topical corticosteroids

45. Stasis Dermatitis: Treatment
Important to treat both the dermatitis and the underlying venous insufficiency
Application of super-high and high potency steroids to area of dermatitis under a wrap
Elevation (to reduce edema)
Compression therapy with leg wraps*
Change wraps weekly, or more often if the lesion is very weepy
* Establish pedal pulses prior to using compression wraps. See the Stasis Dermatitis and Leg Ulcers module for more information.

46. Case Four (cont.)
Mrs. Strong returns for a follow-up visit 6 months later. She was able to adhere to the regimen of topical corticosteroids, leg elevation and compression therapy for the first few weeks, but then became preoccupied with a new grandbaby and stopped the treatment altogether.
A few months later she noticed a weeping wound on the same leg. She has been applying an over-the- counter topical ointment.
She now reports mild pain and worsening pruritus.

47. Case Four: Exam Vital signs: normal
Skin: erythematous plaque located on the medial left leg with a shallow ulcer with a fibrinous base and some serous exudate

48. Case Four, Question 4 What is the most likely diagnosis? Cellulitis
Contact dermatitis
Necrotizing fasciitis
Vasculitis

49. Case Four, Question 4 Answer: b What is the most likely diagnosis?
Cellulitis (history of topical ointment and pruritus are more consistent with contact dermatitis, also patient is afebrile)
Contact dermatitis
Necrotizing fasciitis (would expect fever and other systemic signs and symptoms)
Vasculitis (would expect palpable purpura)

50. Contact Dermatitis
Mrs. Strong has a contact dermatitis secondary to an over-the-counter antibiotic ointment.
Patients with leg ulcers have a high incidence of allergic contact dermatitis due to frequent and prolonged use of topical products as well as a disrupted skin barrier in the areas of use.
Leg ulcers may become persistent or recurrent due to ongoing dermatitis and exposure to contact allergens.

51. Case Four, Question 5
Which of the following recommendations would you provide Mrs. Strong?
Compression therapy
Leg elevation
Local wound care with semi-permeable primary dressing
Stop topical antibiotics
Topical corticosteroids to dermatitis
All of the above

52. Case Four, Question 5 Answer: f
Which of the following recommendations would you provide Mrs. Strong?
Compression therapy
Leg elevation
Local wound care with semi-permeable primary dressing
Stop topical antibiotics
Topical corticosteroids to dermatitis
All of the above

53. Case Five
Ms. April Kapp

54. Case Five: History and Exam
Ms. Kapp is a 72-year-old woman who presents to her primary care provider with a “very itchy rash” on her lower extremities.
Skin Exam: well-marginated plaque with cracking of the skin resembling a dried lake bed

55. Case Five, Question 1
Which of the following history items likely contributes to her condition?
Bathing daily with soap
Her age - elderly
Using the heater during the winter
All of the above

56. Case Five, Question 1 Answer: d
Which of the following history items likely contributes to her condition?
Bathing daily with soap
Her age - elderly
Using the heater during the winter
All of the above

57. Diagnosis: Asteatotic Dermatitis
Also called Xerotic Eczema
Common pruritic dermatitis caused by the loss of the epidermal water barrier
More common in the elderly
Worsened by frequent hot showers, deodorant soaps
Worse in the winter (low humidity of heated houses) and in higher altitudes

58. Asteatotic Dermatitis
Affects lower legs, flanks, arms
Spares armpits, groin, face
Early signs:
flaking of the skin, pruritic
Evolved:
cracking of the skin looking like the bed of a dry lake
itchy and stings
Can become severe:
weepy dermatitis, pruritic

59. Asteatotic Dermatitis: Evaluation and Treatment
Diagnostic Pearl
Pruritus is relieved by prolonged submersion in bath ( minutes). Pruritus then resumes 5-30 minutes after getting out of the water.
Treatment
Moisturize with emollient ointments
Soap to the axillae, groin, scalp only
Medium potency topical steroid ointment to the areas of erythema and pruritus
Severe cases: soak in tub 20 minutes, apply medium potency topical ointment, covered with occlusive dressing overnight

60. Common Causes of the Red Leg
Infection
Vasculitis
Stasis dermatitis
Contact dermatitis
Asteatotic dermatitis

61. What’s the Diagnosis? A B

62. Contact Dermatitis A
Bilateral red plaques surrounding central erosions/ulcers involving the dorsal feet and anterior shins

63. Asteatotic DermatitisB
Erythematous plaque on the skin with a “dried river bed” appearance

64. What’s the Diagnosis? C D

65. Stasis Dermatitis C
Bilateral lower extremity edema with violaceous, symmetrical plaques, scaling and lichenification

66. Leukocytoclastic VasculitisD
Petechiae and erythematous papules densely scattered over the posterior legs.
Non-blanching (not shown)

67. What’s the Diagnosis? E F

68. Necrotizing Fasciitis
Erythematous plaque on the anterior thigh with dusky, necrotic areas and a few overlying flaccid bullae

69. Cellulitis
Erythematous, edematous, confluent plaque on the leg with a central bulla and lymphangitic streaking F

70. Take Home Points
It is important to recognize and treat cellulitis early
Necrotizing fasciitis is a medical and surgical emergency with up to a 20% fatality rate
Leukocytoclastic vasculitis presents as palpable purpura and is secondary to a variety of causes including medications
The treatment of stasis dermatitis includes elevation, compression, topical steroids, and the avoidance of topical antibiotics
Asteatotic dermatitis is a pruritic dermatitis that occurs more commonly in the elderly

71. Acknowledgements
This module was developed by the American Academy of Dermatology Medical Student Core Curriculum Workgroup from
Primary authors: Sarah D. Cipriano, MD, MPH; Eric Meinhardt, MD; Timothy G. Berger, MD, FAAD; Lindy Fox, MD, FAAD.
Peer reviewers: Daniela Kroshinsky, MD, FAAD; Cory A. Dunnick, MD, FAAD; Jenny Swearingen, MD.
Revisions and editing: Sarah D. Cipriano, MD, MPH; Jillian W. Wong. Last revised June 2011.

72. References
Berger T, Hong J, Saeed S, Colaco S, Tsang M, Kasper R. The Web-Based Illustrated Clinical Dermatology Glossary. MedEdPORTAL; Available from:
James WD, Berger TG, Elston DM, “Chapter 14. Bacterial Infections”. Andrews’ Diseases of the Skin Clinical Dermatology. 11th ed. Philadelphia, Pa: Saunders Elsevier; 2011: Fig Necrotizing fasciitis, page 256.
Saap L, et al. Contact Sensitivity in Patients With Leg Ulcerations. Arch Dermatol ;140:
Saavedra Arturo, Weinberg Arnold N, Swartz Morton N, Johnson Richard A, "Chapter 179. Soft-Tissue Infections: Erysipelas, Cellulitis, Gangrenous Cellulitis, and Myonecrosis" (Chapter). Wolff K, Goldsmith LA, Katz SI, Gilchrest B, Paller AS, Leffell DJ: Fitzpatrick's Dermatology in General Medicine, 7e:
Wolff K, Johnson RA, "Section 2. Eczema/Dermatitis" (Chapter). Wolff K, Johnson RA: Fitzpatrick's Color Atlas & Synopsis of Clinical Dermatology, 6e: