Treatment with T-DM1 is relatively safe and well tolerated, however, side effects have been described that have required dose reduction or have led to discontinuation of treatment; the most frequently described side effect is thrombocytopenia [7] followed by elevation of liver enzymes (AST and ALT), hemorrhage, epistaxis, headache, nausea and fatigue [3]. The gene discussed is GPT; the disease is Thrombocytopenia.