Herein, we describe an unusual presentation of acute graft versus host disease (GVHD) mimicking contact dermatitis in an infant who underwent 5/6 HLA-matched bone marrow transplantation (BMT) from his mother for malignant infantile osteopetrosis. The initial rash on day +32 simulated diaper rash, which progressed to a belt-shaped rash and then developed hyperkeratotic nodules on the hands. The acute GVHD was atypical and the course was progressive and fatal, with liver and gut involvement. This presentation of atypical initial skin involvement of acute GVHD may be useful for practicing clinicians in the BMT field who need to be aware of the early unusual signs of acute GVHD so that they can initiate prompt treatment.