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Erythema Nodosum 

Erythema nodosum (EN) is a nodular erythematous eruption that is usually limited to the extensor aspects of the extremities. EN represents a hypersensitivity reaction to a variety of antigenic stimuli and may be observed in association with several diseases (infections, immunopathies, malignancies) and during drug therapy (with halides, sulfonamides, oral contraceptives). Approximately 50% of cases are idiopathic. The clinical picture is that of a nonspecific systemic illness, with low-grade fever (60%), malaise (67%), arthralgias (64%), and arthritis (31%). Laboratory tests show no specific abnormalities except those related to an underlying disease. Familial EN is reported, with affected family members showing a common haplotype. The incidence has decreased in the antibiotic era. EN is seen more frequently in erythema nodosum (EN) is a nodular erythematous eruption that is usually limited to the extensor aspects of the extremities. EN represents a hypersensitivity reaction to a variety of antigenic stimuli and may be observed in association with several diseases (infections, immunopathies, malignancies) and during drug therapy (with halides, sulfonamides, oral contraceptives). Approximately 50% of cases are idiopathic. The clinical picture is that of a nonspecific systemic illness, with low-grade fever (60%), malaise (67%), arthralgias (64%), and arthritis (31%). Laboratory tests show no specific abnormalities except those related to an underlying disease. Familial EN is reported, with affected family members showing a common haplotype. The incidence has decreased in the antibiotic era. EN is seen more frequently in erythema nodosum.

Clinical manifestations and course.

Prodromal symptoms of fatigue and malaise or symptoms of an upper respiratory infection precede the eruption by

Arthralgia occurs in more than 50% of patients and begins during the eruptive phase or precedes the eruption by 2 to 8 weeks. Symptoms may disappear in a few weeks or persist for 2 years, but

The eruptive phase begins with flulike symptoms of fever and generalized aching. The characteristic lesions begin as red, nodelike swellings over the shins; as a rule, both legs are affected. Similar lesions may appear on the extensor aspects of the forearms, thighs, and trunk. The border is poorly defined,

Pathogenesis and etiology.

Erythema nodosum is probably a delayed hypersensitivity reaction to a variety of antigens; circulating immune complexes have not been found in idiopathic or uncomplicated cases. EN is a nodosum is probably a delayed hypersensitivity reaction to a variety of antigens; circulating immune complexes have not been found in idiopathic or uncomplicated cases.

Coccidioidomycosis (San Joaquin Valley fever) is the most common cause of EN in the west and

Histoplasmosis, blastomycosis, and lymphogranuloma venereum may cause EN. Leprosy is another

ERYTHEMA NODOSUM--THE MOST COMMON CAUSES

INFECTIONS
Streptococci
Tuberculosis
Psittacosis
Yersiniosis
Lymphogranuloma venereum
Cat-scratch disease
Coccidioidomycosis
Upper respiratory infection

DRUGS

Sulfonamides
Bromides
Oral contraceptives
SYSTEMIC ILLNESSES
Sarcoidosis
Inflammatory bowel disease
Hodgkin's disease
PREGNANCY