This form occurs, in young subjects, after a streptococcal infection, usually tonsillar. Due to the fact that it initially manifests with a throat infection, it can be considered a simple sore throat and treated with normal antibiotics, when instead there is also inherent inflammation and the consequent presence of patches on the skin.
Papules appear on the skin from 1mm to 1cm in diameter, disseminated above all on the trunk but also on the limbs, with a flaked raindrop aspect and cause itching that inevitably worsens the lesions. In classical cases, 10-15 days before the eruption the patient had an episode of streptococcal pharyngotonsillitis.
In fact, it is believed that there is a structural similarity between the keratin and the M6 protein of streptococcus, so that, in case of infection, the T lymphocytes are activated in the skin, which is able to initiate the psoriatic reaction. In confirmation of the relationship between streptococcus and psoriasis, after a reclamation with antibiotic or tonsillectomy, there is a spontaneous regression of this form of psoriasis.