A 26-year-old girl came to the clinic with painful red nodules on the front of her legs. She has been suffering from fever since a week with a dry non-productive cough. She also complains of pain in all her joints. Her PCP gave her non-steroidal anti inflammatory agents and it did not control her pain or the swellings. A PPD was placed and it read positive at 48 hours. An X Ray of the chest revealed right-sided apical fibrocavitary lesion. On eliciting a detailed history it is noted that her boyfriend had recently been diagnosed to be HIV positive.


The diagnosis of the painful and tender leg swelling is

  1. Erythema multiforme
  2. Erythema nodosum
  3. Erythema subitum
  4. Erythema infectiosum

Answer: The answer is (b). Erythmea nodosum is characterized by painful red swellings without ulceration on the anterior aspect of the legs. It regresses slowly over several weeks. It affects women more often than men. This disease is associated with several infections such as streptococcus, coiccidioidomycosis and deep fungal infections.  E multiforme is characterized by target lesions and lymphadenopathy. When it affects mucus membranes, it is severe and known as Steven Johnsons syndrome - needing hospitalization. Erythema infectiosum is Fifth disease (slapped cheek) caused by Parvovirus B19. It can cause aplastic anemia in patients with hemolysis.

Erythema subitum or Roseola is caused by HHV 6. It is characterized by high fever lasting for 3-5 days, runny nose, irritability and tiredness. As the fever subsides a rash  may appear on the face and body. is also known as roseola infantum


The histological features of this condition is best described as:

  1. Leukocytes infiltration with dermal inflammation
  2. Subcutaneous inflammation with leukocyte infiltration
  3. Septal panniculitis
  4. Lymphatic inflammation

Answer: The answer is (c). The characteristic histological feature of erythema nodosum is septal panniculitis. This is inflammation of the septal region of the adipose tissue.


One important test to work up her underlying clinical condition would be:

  1. Biopsy of the tender nodules
  2. Bronchoscopy, lavage and histology
  3. ELISA for HIV antigen
  4. Serum Angiotensin Converting Enzyme levels

Answer: The answer is (c). This woman has history of possible exposure to HIV, given the history of her boyfriend being recently diagnosed to be HIV positive. She also has an infection, namely tuberculosis that is one of the emerging opportunistic infections in patients with AIDS. The reason for her erythema nodosum is the tuberculosis infection. Therefore the most important test for working up her underlying condition is HIV ELISA.


Treatment specific to this condition includes:

  1. Intralesional corticosteroid injections
  2. Saturated Potassium Iodide solution
  3. Oral steroids – Prednisolone
  4. Anti retroviral therapy

Answer: The answer is (b). The first step in the treatment of erythema nodosum is identifying the root cause and treating it. In this case the cause for the erythema nodosum is tuberculosis and therefore anti tuberculosis treatment is the first line. Primary therapy is with non-steroidal anti-inflammatory agents. This has already been initiated in this patient. Saturated solution of potassium iodide is indicated and it causes prompt resolution of the lesions. There is no role for Intralesional corticosteroids.

Hepatitis B vaccine is very important for all health care workers and other people who are constantly in contact with infective body fluids. This is probably the single most important health promotion and disease prevention method that prevents a deadly cancer, namely cancer of the liver.