An 86-year-old woman presented with a chronic granulomatous skin lesion on
the dorsal aspect of her left hand. Histologic examination showed pseudoepi
theliomatous hyperplasia and a dense dermal infiltrate largely composed of
lymphocytes and histiocytes. Abscess formation and fibroblastic proliferati
on were also present. Use of Fite, Giemsa, and periodic acid-Schiff stains
did not show specific organisms. The gram-negative bacillus Serratia marces
cens was the only microorganism isolated from all cultures performed. Trime
thoprim-sulfamethoxazole, 960 mg every 12 hours for 20 days (orally), was g
iven and resulted in complete disappearance of the lesion and negative cult
ure findings. Cutaneous infection by S marcescens may represent a distincti
ve entity, whose clinical and possible pathogenic features are presented he
re.