Another nasty case of diarrhoea !

This is the sigmoid colon and rectum of a young patient who have just undergone bone marrow transplantation. 
WHAT IS THE LIKELY DIAGNOSIS?

■ Graft versus host disease

You don't get ulcers in GVHD!

■ Checkpoint inhibitor colitis

You DO get ulcers with these but they wouldn't be used!

■ Pseudomembranous colitis

Doesn't cause ulceration

■ CMV colitis

Absolutely !

■ Herpetic colitis

Hmm, does this actually happen?!

explanation

In GVHD there are minimal mucosal changes whilst there is extensive ulceration in this case. You do get nasty mucosal ulceration with checkpoint inhibitors but these drugs would not be used in transplantation.  C.diff doesnt' cause mucosal ulceration and the herpes virus does not infect columnar mucosa.  This leaves CMV ! 

Cytomegalovirus is a herpes virus that infects the majority of humans. Primary infection in individuals with normal immune function is usually asymptomatic or result in mononucleosis-like syndrome (fever, lymphadenopathy, and atypical lymphocytosis on a blood film).

After primary infection, CMV becomes latent in various host cells but are controlled by a functioning immune system. When re-activation occurs in patients with severely compromised immune function (transplant patients or patients with AIDS and CD4 count <50 cells/microlitre), uncontrolled CMV replication can ensue leading to fever, bone marrow suppression, and tissue-invasive disease, depending on where the reactivated cells are residing.

Investigations includes serology, pp65 antigenaemia test, histopatholical analysis of any tissue obtained, and PCR based detection. 

Treatment of choice is oral valganciclovir or intravenous ganciclovir whilst IV foscarnet and cidofovir are second line agents.