Bone marrow aspirate (A, May-Grunwald Giemsa stain, ×400) and biopsy (B, Haematoxylin-eosin stain, ×400) of patient 2 showing myeloid maturation arrest. A colonic biopsy showed cytomegalovirus (CMV) inlusion bodies (C, Haematoxylin-eosin stain, ×400) and CMV immunohistochemical positivity (D, ×400).