Persistent narrowing of the foreskin, not allowing to completely expose the glans penis. It can be congenital and acquired, for example, due to cicatricial changes in the foreskin in chronic balanoposthitis.
In newborns, phimosis is a physiological phenomenon. By 2-3 years, loose adhesions between, the glans penis and foreskin are destroyed and its ring expands. Violation of this process leads to phimosis. Forced exposure of the head can lead to pinching it with the foreskin ring (paraphimosis). Treatment of phimosis is only surgical - the foreskin is excised.