Perianal cellulitis also known as perianal streptococcal dermatitis is an infection which is particularly caused by group A betahemolytic streptococci. However, a variety of other aerobic and anaerobic microorganisms had been reported to be capable of causing perianal cellulitis. Induction and/or exacerbation of guttate psoriasis may follow streptococcal infection of the pharynx or perianal region. Although the association between prior infection with group A streptococci and guttate psoriasis is well known, previous studies suggest that the ability of streptococci to trigger guttate psoriasis is not group or serotype specific. Here we report a patient with perianal cellulitis due to group B streptococci, who had a concurrent flare of guttate psoriasis.