• E Routier, S Bularca, E Sbidian, J-C Roujeau, and M Bagot.
• Service de dermatologie, hôpital Henri-Mondor, AP-HP, 94010 Créteil, France. routieremilie@hotmail.com
• Ann Dermatol Vener. 2010 May 1;137(5):369-72.

BackgroundPsoas abscess is a rare clinical entity that occurs chiefly after intra-abdominal or retroperitoneal infection. We report two cases of psoas abscesses caused by group A beta-haemolytic streptococcal infection having a cutaneous portal of entry.Case ReportsThe first patient, a 50-year-old man, was feverish and had ulcerative and necrotic cutaneous lesions evocative of ecthyma that were progressing for three months and were recently associated with a painful mass in the left iliac fossa, leading to difficulties in walking. The second patient, a 35-year-old woman with a medical history of intravenous drug addiction, was admitted to intensive care for sepsis syndrome following group A beta-haemolytic streptococcal infection with a cutaneous portal of entry (swelling on left lower limb). She remained unaccountably subfebrile 10 days after the start of antibiotic therapy with amoxicillin. Abdominal CAT scans for each patient confirmed the diagnosis of left psoas abscess. For the first patient, the same group A beta-haemolytic streptococcus was isolated in drainage fluid and at the cutaneous injury site. The outcome was favourable in both cases following extensive intravenous antibiotic therapy (amoxicillin) combined with percutaneous drainage (in the first case).DiscussionPsoas abscess can occur after locoregional infection and the portals of entry are usually gastro-intestinal, musculoskeletal or genitourinary, with many organisms capable of causing such secondary abscesses. Psoas abscess can also be a primary clinical event. Staphylococcus aureus is the most common causative organism. The presented cases comprised secondary psoas abscesses with a cutaneous portal of entry. Since the complete set of three evocative symptoms (prolonged fever, pain and psoitis) is frequently seen late, diagnosis must be made on the basis of prolonged infectious state or unaccountable feverish abdominal pain. Diagnosis is based on abdominal CAT scan and treatment involves the use of appropriate antibiotics as well as percutaneous or surgical drainage of the abscess. The mortality rate in this patient population remains high with survival being dependent on prompt initiation of therapy.Copyright 2010 Elsevier Masson SAS. All rights reserved.

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