1A, B). H & E stain from a biopsy of one nodule showed normal

tissue being replaced by anaplastic cells suggestive of a malignancy, and ICH for placental alkaline phosphatase was positive indicating a primary germ cell tumour (probably a metastasis) of unknown location. (Fig. 1C, D, respectively). Despite this, ERT was continued along with palliative therapy for pain management until the patient eventually died at the age of 67 months due to septic shock. To investigate the molecular basis SB525334 cell line of immune deficiency in the patient, we obtained genomic DNA from whole blood and buccal epithelial cells at the age of 30 months, and sequenced all the exons of the ADA gene. As shown in Fig. 2 (upper panel, A and B), a homozygous missense Vemurafenib chemical structure mutation in

exon 4 was found (g.29009 T > C) that leads to a replacement of a leucine for a proline in the position 107 of the protein (L107P). This mutation has been reported previously and results in ≤0.05% of ADA activity in vitro, correlating with the clinical phenotype of severe early-onset ADA deficiency in our patient [5]; in addition, both parents were heterozygous for this mutation (Fig. 2 upper panel, C and D). We also measured ADA activity in the blood spots obtained from the patient and found no activity on his RBC (0 vs. 25.5 nmol/h per mg protein in the control) (Table 2, 30 months old); moreover, both parents showed approximately MRIP half of the ADA activity observed in the healthy control. However, dAXP were modestly elevated (14.1% vs. 0% for

the healthy control and 50.3 ± 18% for patients with ADA-SCID), and this finding is more consistent with a delayed-onset phenotype. An unexpected increase in the numbers of T lymphocytes in patients with SCID could be explained either by spontaneous engraftment of maternal lymphocytes or alternatively, by transfusion of HLA-mismatched non-irradiated blood products [3]. As no records of previous blood transfusions were found, we karyotyped the PBL and performed HLA typing on the patient and his parents and found that he was both 46 (X, Y) and HLA haploidentical to his parents, excluding maternal and transfusion-related engraftment of T cells (data not shown). The possibility of somatic mosaicism caused by a de novo mutation was excluded because both parents were carriers of the same mutation (Fig. 2). A small number of ADA-deficient patients reported to date exhibit variable counts of T lymphocytes that result from an in vivo reversion of inherited mutations in the ADA gene [9–13].