This case was reported in a literature article and described the occurrence of aplastic anemia in a 34-year-old male patient who received DTPa. On an unknown date, the patient received DTPa vaccine (unknown). On an unknown date, 30 days after receiving DTPa vaccine, the patient experienced aplastic anemia (serious criteria GSK medically significant), increased tendency to bruise, petechia and pancytopenia (serious criteria GSK medically significant). On an unknown date, the outcome of the aplastic anemia, increased tendency to bruise, petechia and pancytopenia were not recovered/not resolved. The reporter considered the aplastic anemia, increased tendency to bruise, petechia and pancytopenia to be almost certainly related to DTPa vaccine. Additional information received: This case was reported in a literature article and it described the occurrence of aplastic anaemia in a 34-year-old male subject who had received an unspecified Tdap vaccine (manufacturer unknown). The subject was reported to be healthy prior to the event and had no history of fevers, chills, weight loss or exposure to pesticides, hazardous chemicals or radiation. He was not taking any concomitant medication or supplements. No further information on the subject's medical history, concurrent medical conditions or concomitant medication was provided. On an unspecified date, the subject received a dose of an unspecified Tdap vaccine (dosage, administration route and site unknown; batch number not provided) following the birth of his child. On an unspecified date, 1 month after the administration of the vaccine, the subject developed easy bruising and petechiae. He presented to his primary care physician with this symptoms 4 weeks later where he was diagnosed with pancytopenia. The results of a full blood count performed on his first presentation were: haemoglobin 9.4 g/dL, platelet count 14,000 cells/mcL and white blood cells 3.9 with lymphocyte predominance (60%). HIV, hepatitis, cytomegalovirus, Epstein-Barr virus, B12/folate, antinuclear antibodies and parvovirus B19 tests were all negative. No splenomegaly was noted on abdominal ultrasound. A bone marrow biopsy showed his marrow cellularity to be 30%, with normal morphology to be residual hematopoietic cells. Flow cytometry showed normal myeloid granularity without increase in myeloid immaturity and without lymphocytic immunophenotypic abnormalities. Serial full blood counts were performed for weeks after the initial findings with no improvement in his results. Treatment was unknown. At the time of reporting the event was ongoing. The authors described the event as caused by the vaccine. The authors concluded that "This case illustrated the diagnostic difficulties associated with identifying the source of aplastic anaemia. In this case, the authors suspected the cause to be secondary to the Tdap vaccine the subject received a month prior to his symptoms. Multiple case reports have been cited linking vaccines to aplastic anaemia including varicella, hepatitis B, anthrax and influenza, but none secondary to the Tdap vaccine. The hypothesized theory for this would be an underlying immune predisposition may have enabled the vaccine to trigger vigorous cytotoxic T lymphocyte response that possibly led to the aplastic anemia. Though the benefits of vaccines clearly outweigh the risks of developing aplastic anaemia, physicians should be cognizant of the possible effects."