I am shut up. — Not necessarily an actual imprisonment or incarceration on account of leprosy, but another figurative way of describing great trouble. Job 19:8 seems to have been before the poet.
Related Commentaries of Psalms 88:8
Psalms 88:8
8 Thou hast put away mine acquaintance far from me; thou hast made me an abomination unto them: I am shut up, and I cannot come forth.