4. PATHOPHYSIOLOGY
Delayed hypersensitivity reaction to a variety of
antigens
CIC have not been found in idiopathic or
uncomplicated cases
IBD – may show immune complexes
5. HISTOLOGIC FINDINGS
Septal panniculitis -septal
edema and lymphohistiocytic
infiltrate
Miescher’s microgranulomas -
clusters of macrophages
around small vessels or a slit-
like space
Lymphohistiocytic infiltrate
Granuloma and lipogranuloma
formation
6. CLINICAL FEATURES
Erythema nodosum usually starts
with flu-like symptoms of fever and
bodyaches
Arthralgia may precede the
eruptive phase
Red tender nodules usually on the
anterior surface of legs-shins
Other areas- arms, trunk and face
Lesions borders are poorly
defined and vary from
2 cm to 10 cm
1 st week - tense, hard,
red and painful
7. 2nd week - fluctuate and attain a
yellowish hue, resembling a bruise
Do not suppurate or ulcerate
Individual lesions usually last for 2
weeks but occasionally new lesions
appear up to 3–6 weeks
Lesions disappear as the overlying
skin desquamates
Joint tenderness and morning stiffness
may occur.
No destructive changes occur.
Synovial fluid is acellular and
rheumatoid factor (RF) negative
12. STREPTOCOCCAL PHARYNGITIS
Beta-hemolytic streptococcal infections- most common
44% - adults and 48% - in children
EN eruptions-2–3 weeks after an episode of streptococcal
pharyngitis
Should have throat culture evaluation for group A strep.,
as well as strep. antistreptolysin O (ASO) titers or
polymerase chain reaction (PCR) assays, or both
ASO titers should be taken at the time of diagnosis and
then again within 4 weeks to assess for strep. infection
13.
14. TUBERCULOSIS AND
MYCOBACTERIAL INFECTIONS
Erythema nodosum may occur with primary TB
All patients with EN should be stratified by risk for TB
exposure
Antitubercular therapy (ATT) should be initiated for EN in
patients with positive Mantoux skin test reactions
Culture identification from primary sites identifying an
atypical nontuberculous mycobacterium as a cause of EN.
18. LABORATORY DIAGNOSIS
Careful history, physical examination and drug history
Prior diarrheal illness, URTI and any endemic infections
Throat culture—rules out streptococcal infection
CBC and ESR
Antistreptolysin O (ASO)/DNase titer at 2 weeks and 4 weeks interval
Stool examination.
Chest X-ray (CXR)— purified protein derivative (PPD) to rule out
Koch’s, unilateral hilar lymph nodes—Infections and malignancy
CXR to rule out sarcoid—bilateral hilar lymph nodes
Biopsy the lesion to rule out vasculitis—Collagen vascular disease.
19. DIFFERENTIAL DIAGNOSIS
Lupus panniculitis—present in fatty areas such as
buttocks, posterior arms and leave scars
Tuberculous erythema induratum—usually ulcerate
Erythema nodosum leprosum
Acute urticaria—itching is intense
Nodular vasculitis-PAN—look for fixed livedo reticularis
Sarcoidosis
Superficial thrombophlebitis—linear tender streaks
Erysipelas
Filarial lymphadenitis
Insect bites.
25. CHRONIC ERYTHEMA NODOSUM
Chronic EN is a condition in which the lesions pop up
elsewhere for a period of weeks to months
In most of the cases a cause is elusive
TB should be considered in our settings and a trial ATT may
be given
Intense investigations to rule out sarcoid, IBD and collagen
vascular disease (CVD) should be done
Rare association- Takayasu arteritis, vitamin B12 deficiency
and Ehlers Danlos has been reported.
27. THERAPEUTIC LADDER FOR EN
Discontinue possible causative medications
Treatment of underlying infectious diseases mainly
streptococcal and TB
Bed rest and leg elevation and nonsteroidal anti-
inflammatory drugs (NSAIDs) (aspirin, ibuprofen,
indomethacin, naproxen)
Potassium iodide—saturated solution of potassium
iodide-5–15 drops three times a day. Mechanism of
action is exactly not known
Colchicine in the setting of Behçet’s disease
28. Various treatments for IBD like systemic steroids, HCQS, MMF,
cyclosporine, thalidomide, infliximab and etanercept are effective in
managing the underlying EN
Paradoxically both infliximab and etanercept have been reported to
produce EN as a cutaneous side effect.
NSAID are to be avoided in IBD as they aggravate the disease
Systemic steroids - relatively safe therapeutic option if underlying
infection, risk of bacterial dissemination or sepsis and malignancy has
been excluded by a thorough evaluation
A general rule is 1 mg/kg (body weight)/day.
29. USE OF POTASSIUM IODIDE
Saturated solution of potassium iodide 1,000 mg/mL
Droppers - for calibrations: 0.3 mL (300 mg),0.6 mL ( 600 mg)
In adults and older children, common dose = 300 mg TDS with starting
dose = 150–300 mg TDS
Saturated solution of potassium iodide (SSKI)- bitter taste – water or
fruit juice
Crystallization in cold - rewarming and shaking
Discard if solution turns yellow-brown
Side effects: Acute—nausea, eructations, excessive salivation,
urticaria, angioedema, small vessel vasculitis
Chronic—enlargement of salivary and lacrimal glands, acneiform
eruptions, iododerma, hypothyroidism, hyperkalemia and occasionally
hyperthyroidism
30. PROGNOSIS
Erythema nodosum prognosis is excellent
The lesions resolve without any adverse reactions
in most cases
Few cases are recurrent and refractory for which
an underlying cause is to be ascertained and
treated accordingly
Some of the idiopathic cases respond to
colchicine/dapsone on prolonged treatment.
31. CONCLUSIONS
Erythema nodosum is an acute panniculitis
presenting as subcutaneous nodules most
commonly due to infections and responds well to
treatment
Chronic nodules need to be investigated
thoroughly and treated accordingly.
32. ACKNOWLEDGEMENTS
Dr Mala Saranathan ,Dermatologist
Dr G Srihari , Dermatologist
Dr M Srinivas , Pathologist
Dr M Santipriya , Pathologist