<s>[INST] context: This one is about the differential diagnosis of panniculitis.
Panniculitis refers to a broad spectrum of disease that involves inflammation of the fatty layer of the skin


The tissue layer under the skin (epidermis and dermis) is called the subcutaneous fat or panniculus.
Inflammation of this layer of fatty tissue is called panniculitis
Due to panniculitis, the overlying skin appears as a red or purplish lump.


Both erythema nodosum and weber Christian disease are characterized by panniculitis.
Their clinical presentation is quite similar and there is not much to separate the two diseases.


Both the diseases present with tender erythematous nodules on the lower legs.
Systemic features such as fever, malaise, weight loss and arthralgia are seen in both the disease.

Facts which favour the diagnosis of erythema nodosum in the question

The lesions in Weber Christian disease are bilateral and symmetrical
The clinical course of Weber Christian disease is characterized by exacerbations and remissions
The involved areas manifest as recurrent crops of erythematous tender nodules.
It is a rare disease and is usually seen in elderly females (30-60 yrs).
The patient in the question gives a history of fever & malaise for 2 weeks which is a classic feature of erythema nodosum (erythema nodosum is associated with preceding streptococcal infection). [/INST] question: 25 years old male having fever & malaise for 2 weeks, arthritis of ankle joint and tender erythema-tons nodules over the shin. Diagnosis is – | options: A: Erythema nodosum B: Hensen's disease C: Weber–christian disease D: Urticarial vasculitis | answer: A </s>