A more abbreviated mnemonic would be DISSTend
Drugs (remember "POSH", see below)
IBD / Idiopathic
Streptococcal infection
Sarcoidosis
TB
end = erythema nodosum
A longer, but still non-exhaustive mnemonic is: POSH GUNSMITH
Penicillins
OCPs
Sulfonamides
Halides
Gastroenteritis (Yersinia > Salmonella or Campylobacter)
URTI (viral)
Neutrophilic dermatosis (Behcet's, Sweet's)
Streptococcus / Sarcoidosis
Malignancy (usu Haematologic)
IBD / Idiopathic
TB
HIV / Hep B