This is a fifty-six year old male patient with relapsed T-cell prolymphocytic leukemia 2.5 years after matched unrelated donor stem cell transplantation.

He was initially diagnosed in 2015 with white cell count of 54,400 per microliter at the time with extensive bone marrow infiltration and diffuse lymphadenopathy as well as splenomegaly. Flow cytometry at that time demonstrated expression of CD45, CD3 and CD4 without CD8.  However when he relapsed with disease after transplant in the skin and bone marrow, there was a change in phenotype with notable double expression of CD4 and CD8 with loss of CD45.

He was on anti-CD52 therapy since the most recent relapse with addition of pentostatin and bendamustine subsequently but with progressively rising blood counts and lymphocytosis. The slides and flow plots since this therapy after relapse are depicted below.

Learning point from case below:
1. T-PLL often shows blebs as noted in the smears below and presents with high counts in the blood.
2. Change in phenotype may occur in T-cell processes, so careful attention must be paid to such changes at relapse.