Lymphatic involvement is often manifested by overlying skin streaking and regional lymphadenopathy. More severe infections may exhibit numerous vesicles and bullae along with petechiae and even frank necrosis. With treatment, the lesion often desquamates and can resolve with pigmentary changes that may or may not resolve over time. Staphylococcus aureus has been implicated in cases of recurrent erysipelas secondary to lymphedema. Recently, atypical forms have been reportedly caused by Streptococcus pneumoniae , Klebsiella pneumoniae , Haemophilus influenzae , Yersinia enterocolitica and Moraxella species, and should be considered in cases refractory to standard antibiotic therapy.
Cellulitis has no lymphatic component and exhibits indiscreet margins.
Routine complete blood count with differential is indicated as neutrophilic leukocytosis is common. Blood, wound and nasopharyngeal cultures are recommended. Imaging studies are usually not indicated and are of low yield. If bony involvement is suspected, routine x-rays and bone scans are appropriate. The histologic hallmarks of erysipelas are marked dermal edema, vascular dilatation and streptococcal invasion of lymphatics and tissues.