Fulminant hepatic failure of unknown origin is the most common cause of fulminant hepatitis with high incidence of aplastic anaemia. Furthermore, the association of liver failure and aplastic anaemia has an increased mortality rate. In this report we describe a 16-month-old boy who presented with aplastic anaemia preceding a non-A, non-B, non-C fulminant liver failure. He developed severe graft versus host disease (GvHD) after liver transplantation, proven by the presence of donor cells in the peripheral blood and in the skin biopsy. He received conventional therapy (steroids, mycophenolate, anti-IL-2 monoclonal antibodies, anti-thymocyte globulin) without success. In an attempt to obtain T cell depletion and reduce the GvHD, he was treated with Alemtuzumab, a first time use for this indication. Aplastic anaemia was extensively investigated, especially exploring the possibility of primary immunodeficiency and reticular dysgenesis which were excluded based on clinical history. However, another form of primary immunodeficiency could be the cause of the uncontrollable proliferation of the donor lymphocytes derived from the liver transplant. Despite aggressive treatment GvHD progressed and the patient died of multiorgan failure. The majority of authors mention aplastic anaemia as a secondary event post liver transplant, whereas in our view this might be a haematopoietic stem cell disorder preceding fulminant hepatic failure. These patients also need to be evaluated extensively in order to exclude a primary immunodeficiency. The underlying disease will determine the choice of immunosuppressive treatment, especially in case of development of GvHD caused by the transplanted lymphocytes inhabiting the donor liver.