title: Lesion mimicking perianal abscess in an immunocompromised patient: Report of a case.
abstract: BACKGROUND
  Ischiorrectal tumoral masses mimicking perianal abscess and abscess from uncommon microbiological origins have previously been reported.
  
  
  METHODS
  Unusual perianal abscess arising from an hematoma in an elderly woman with myelodysplastic syndrome: the patient presented on the emergency with gluteal pain and fever after intramuscular injection of analgesic drug. Physical examination revealed subcutaneous thickening on gluteus and perianal region, without skin changes. Magnetic resonance reported an heterogeneous mass sized 5cm×12cm×20cm from gluteus maximus to ischioanal fat under levator ani muscle, through sciatic notch. Debridement of an staphylococceal infected hematoma through a single left lateral gluteus incision, and primary closure was performed. Proctologic examination was normal, so any perianal incision was done. The site infection progressed, so the patient required new surgery with wet cure. The patient contracted nosocomial pneumonia and died due to sepsis.
  
  
  CONCLUSIONS
  Hematological diseases can yield infectious and bleeding disorders. Intramuscular injections often cause haematomas that can lead to pyomyositis. Pyomyositis requires early debridement and continue cure.
  
  
  CONCLUSIONS
  Intramuscular administration of drugs should be avoided in patients with thrombocytopenia. Gluteal region is connected to perianal area through the sciatic notch. Usually perianal abscess in immunocompromised patients arise from proctologic origin, but other causes may be taken into account.
authors.affiliation: Hospital Vall d'Hebron, Institut Català de la Salut, Passeig de la Vall d'Hebron, 119-129, Barcelona 08035, Spain. Electronic address: aranzazucalerolillo@gmail.com.
authors.forename: Aranzazu
authors.initials: A
authors.lastname: Calero-Lillo
authors.affiliation: Hospital Vall d'Hebron, Institut Català de la Salut, Passeig de la Vall d'Hebron, 119-129, Barcelona 08035, Spain. Electronic address: enriccaubet@gmail.com.
authors.forename: Enric
authors.initials: E
authors.lastname: Caubet
keywords: Perianal mass; Pyomyositis