The patient seroconverted after two months of alglucosidase alfa with anti-rhGAA IgG antibody titer of 1 1:100, but antibody levels remained low through continued treatment with maximum level of 1:3200 at 12?weeks. more youthful sibling. We spotlight the significant difference in clinical program between the two patients, particularly that a pre-emptive approach was simple and effective in preventing the development Edicotinib of high antibody titers in Edicotinib the younger sibling, therefore supporting the part of immune tolerance induction (ITI) in the ERT-na?ve high-risk setting. was a 10-month-old African American male born full term and diagnosed like a neonate with vintage IPD. Shortly after Edicotinib birth, he developed supraventricular tachycardia with WolffCParkinsonCWhite syndrome and hypertrophic cardiomyopathy. These findings, in addition to slight macroglossia and hypotonia, prompted evaluation for IPD. Genetic testing shown a missense switch in allele 1 (c.2105G? ?T) and a nonsense mutation in allele 2 (c.2512C? ?T) in the gene. Parental screening confirmed that every parent carried one mutation. The missense mutation in allele 1 results in leucine replacing arginine 702 (p.Arg702Leu), a nucleotide switch reported previously in only one individual with Pompe disease . The mutation in allele 2 was expected to result in a premature quit (p.Gln838X), a nucleotide switch not previously reported but predicted to be disease causing. CRIM status was identified as CRIM-positive by European blot analysis (Integrated Genetics). Treatment with alglucosidase alfa (20?mg/kg every 2?weeks) was initiated at age 23?days with improvement in clinical status, particularly LVMI (Fig. 1). Swallow study like a neonate shown aspiration, consequently he received feeds via a nasogastric tube. Seronegative status was confirmed prior to initiation of ERT. After approximately 5?months of ERT, the patient developed detectable anti-rhGAA IgG antibodies, initially at a titer of 1 1:25,600 (Fig. 1). He then developed HSAT with titer of 1 1:102,400 on two occasions with concomitant worsening of medical status. Treatment having a bortezomib-based ITI was initiated based on published data  around 11?weeks of age with subsequent decrease in antibody titers. Three and a half weeks into ITI, bortezomib was repeated (due to antibody titer remaining at 1:51,200) resulting in a subsequent decline to 1 1:1200. CD19+ B-cells decreased to ?1% of total while blood cell (WBC) count approximately 2?weeks from the start of ITI and remained ?1% (Table 1). Rituximab was weaned to every 8?weeks beginning LEF1 antibody approximately 9?months into ITI. Table 1 Effect of ITI on percentage and complete number of CD19+ B lymphocytes. was a 3-week-old African American male born full term who was diagnosed with vintage IPD prenatally due to his brother’s known disease status. Genetic screening was performed on prenatal amniocentesis at 18?weeks and demonstrated a missense switch in allele 1 (c.2105G? ?T) and a nonsense mutation in allele 2 (c.2512C? ?T) in the gene (identical to brother’s screening). The analysis was confirmed by blood GAA enzyme level on day time of existence 2. Based upon his brother’s disease phenotype with the development of HSAT despite early initiation of ERT, prophylactic ITI with rituximab, methotrexate, and IVIG was initiated at the time of 1st alglucosidase alfa dose (20?mg/kg every 2?weeks; Fig. 2). Seronegative status was confirmed prior to the initiation of ERT. The patient seroconverted after two months of alglucosidase alfa with anti-rhGAA IgG antibody titer of 1 1:100, but antibody levels remained low through continued treatment with maximum level of 1:3200 at 12?weeks. This was in contrast to the older sibling’s titer of 1 1:204,800 at age of 10?weeks. CD19+ B-cells decreased to ?1% of total WBC three weeks from the start of ITI and normalized by approximately 5?weeks (Table 1). Antibody titers have remained low ranging from 1:200.