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Knee Knots in a Young Girl: What's Your Diagnosis?

Knee Knots in a Young Girl: What's Your Diagnosis?

  • Knee Knots in a Young Girl...well, not exactly on the knee.

  • On a busy clinic day, 6-year-old Polly limped into the outpatient clinic and was admitted because of the painful lumps on her lower legs. You are asked to evaluate her. Her history reveals: a sore throat 4-5 weeks ago; red, very tender nodules over her shins that have been present for 2 weeks.

  • Past medical history: non-contributory. No travel. No recent immunizations. Other than the previous sore throat, no illnesses.No fever, weight loss, bruising.

  • Review of systems. no trauma. not taking any medications. Physical examination is significant only for 1- to 4-cm oval, reddish-brown, easily palpable firm nodules over the surface of the anterior tibia. The overlying skin is tight and starting to peel.

  • Note the nodular lesions on the surface of the anterior tibia and that the overlying skin is peeling.

  • A close-up view of some of the many tender nodules and the peeling of the overlying skin.

  • How about contemplating a differential diagnosis?

  • Differential diagnosis: First, lets eliminate a few categories…based on the history and physical examination, it is not traumatic, or an obvious infection. Could it be a tumor? Could it be an inflammatory condition? Benign and malignant tumors can cause lumps including: Fibroma, lipoma, lymphoma, osteosarcoma, sarcoma. Do any of these seem to fit?

  • Differential diagnosis...Could it be an inflammatory condition? Inflammatory conditions to consider include: Erythema nodosum; gout; pseudogout; osteoarthritis; psoriatic arthritis; rheumatoid arthritis; systemic lupus erythematosus; some other form of vasculitis.

  • Answer: Erythema nodosum. A delayed cell-mediated hypersensitivity. Respiratory etiology most common cause in children. Recent streptococcal infections most common type in children. Remember, there is a 10% recurrence rate. Red, tender nodular lesions most commonly on the pretibial surface of the legs. Not suppurative.

  • Erythema nodosum. Histopathologic features: lymphocytic perivascular infiltrate in dermis. lymphocytes & neutrophils in the fibrous septa; in subcutaneous fat. If you make the clinical diagnosis, however, histology is not likely to be required

  • Erythema nodosum: etiology. Infections: Infections: group A B-Strep, infectious mononucleosis influenzae, herpes, tuberculosis, histoplasmosis, coccidiomycosis, cat scratch disease, leprosy. psittacosis, lymphogranuloma venereum, measles, ascariasis, leishmaniasis. Also ulcerative colitis, pancreatitis.

  • Erythema nodosum etiology, continued. Malignancy: leukemia, hodgkin, non-hodgkin. Collagen-vascular: systemic lupus erythematosus, polyarteritis nodosa, sarcoidosis. Drug-induced: Sulfonamides, oral contraceptives, salicylates, thiazides, dilantin, iodides, bromides, phenacetin.

  • Erythema nodosum etiology: Biologicals: bacille Calmette-Guerin vaccine, diphtheria antitoxin and toxoid, pure pollen extracts, vaccines.

  • There are times when erythema nodosum is somewhat atypical...It is important, then, to remember that erythema nodosum falls into the category of panniculitis...

  • Represents infiltration of subcutaneous tissues by inflammatory and / or neoplastic cells. Apparent as deep induration or swelling of the skin. Associated signs include erythema, ulceration, drainage, warmth, and pain or tenderness.

  • Erythema nodusum is a septal panniculitis. Predominance of inflammation involves the connective tissue septa between the fat lobules. Lobular panniculitis: inflammation is of the fat lobules themselves.

  • Septal panniculitis: erythema nodosum, subacute nodular migratory panniculitis (scleroderma) Lobular and mixed panniculitis: Vasculitis and connective tissue, lupus, erythema induratum, other connective tissue. Lobular and mixed panniculitis: Metabolic: altered melting points of fat in the newborn, seen in subcutaneous fat necrosis and sclerema, pancreatic, alpha-1-antitrypsin deficiency. Traumatic. Infectious. Malignancy. Lipodystrophy.

Polly is 6-years-old and is admitted to hospital for painful red nodules on her shins that have been present for 2 weeks. She has no fever, has not been immunized recently, and has no travel history. She had a sore throat a few weeks ago but that has resolved. What's causing the painful lesions on her legs?

It's another in our series of thought-provoking cases from Dr Jonathan Schneider. The well- considered differential diagnosis is key to resolving his cases and he walks you deliberately through the details. Trauma? Tumor? Inflammatory condition? Follow the slides above and find out.





Suggested reading

 ► Schwartz RA, Nervi SJ. Erythema nodosum: a sign of systemic disease. Am Fam Physician. 2007;75:695-700.

 ► Requena L, Sánchez Yus E. Erythema nodosum. Semin Cutan Med Surg. 2007;26:114-125.

 ► Kakourou T, Drosatou P, Psychou F, Aroni K, Nicolaidou P. Erythema nodosum in children: a prospective study. J Am Acad Dermatol 2001;44:17-21.

 ► Labbe L, Perel Y,  Maleville J, Taieb A. Erythema nodosum in children: a study of 27 patients. Pediatr Dermatol 1996;13:447-450.

 ► Requena L, Requena C. Erythema nodosum. Dermatol Online J. 2002;8(1):4.




Good job

muslim @

Would like to see more of these mysteries

ricky @

Would like to see more of these mysteries

ricky @

Erythema nodosum

Elsie @

Henoch Schonlein purpura.
Had a similar case referred to me as possible acute appendicitis, child
with abdominal pain and WBC 25,000. Had red bumps on the shins, and as
I recall, antecedent sore throat. Perhaps some joint pain (good # of years ago)

Recovered without surgery (or my surgical fee)

charles @

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