Kelly A. Shaw

Newborn Screening for Galactosemia in the United States: Looking Back, Looking Around, and Looking Ahead

It has been 50 years since the first newborn screening (NBS) test for galactosemia was conducted in Oregon, and almost 10 years since the last US state added galactosemia to their NBS panel. During that time an estimated >2,500 babies with classic galactosemia have been identified by NBS. Most of these infants were spared the trauma of acute disease by early diagnosis and intervention, and many are alive today because of NBS. Newborn screening for galactosemia is a success story, but not yet a story with a completely happy ending. NBS, follow-up testing, and intervention for galactosemia continue to present challenges that highlight gaps in our knowledge. Here we compare galactosemia screening and follow-up data from 39 NBS programs gathered from the states directly or from public sources. On some matters the programs agreed: for example, those providing relevant data all identify classic galactosemia in close to 1/50,000 newborns and recommend immediate and lifelong dietary restriction of galactose for those infants. On other matters the programs disagree. For example, Duarte galactosemia (DG) detection rates vary dramatically among states, largely reflecting differences in screening approach. For infants diagnosed with DG, >80% of the programs surveyed recommend complete or partial dietary galactose restriction for the first year of life, or give mixed recommendations; <20% recommend no intervention. This disparity presents an ongoing dilemma for families and healthcare providers that could and should be resolved.

A brief overview of galactosemia newborn screening in the United States

Dear Editor, In the United States in the past 50 years an estimated >2500 infants with classic galactosemia (CG) (Fridovich-Keil and Walter 2008) have been identified by newborn screening (NBS). Most of these babies were spared the trauma of potentially lethal acute disease by early diagnosis and intervention; many are alive today because of NBS. Newborn screening for galactosemia is a success story, but continuing disparities between states in their approach to NBS, follow-up testing, and intervention for variant forms of galactosemia reveal gaps in our knowledge and highlight opportunities for improvement. To characterize existing disparities we recently collected and compared data from 39 state NBS programs (Pyhtila et al 2014 in press). On some matters the programs we surveyed agreed. All identified CG in close to 1/50,000 newborns and recommended immediate and life-long dietary restriction of galactose for affected infants. On other matters the programs disagreed. For example, median detection rates for Duarte galactosemia (DG), a common and ostensibly mild form of transferase deficiency, varied from 0.4 to 34.7 per 100,000 births; this range largely reflected differences in screening approach. Similarly, NBS in some states was sufficient to detect epimerase or kinase deficiency in addition to transferase deficiency; in other states it was not. Median false positive rates for galactosemia NBS also varied markedly, from as low as 2.0 to as high as 575.5 per 100,000 births. High false positive rates were particularly troubling in some states due to the associated healthcare costs of follow-up testing for so many presumably healthy infants (Fernhoff 2010), and the worry and potential breastfeeding interruption imposed on the families involved. The factor most clearly associated with differential DG and false positive rates was the NBS GALT activity cut-off level. Longitudinal data provided by one state demonstrated that lowering the cut-off from 3.5 to 3.0 U/g Hb did not change the detection rate for CG but lowered the DG detection rate by close to six-fold and the false positive rate by close to ten-fold. This was a striking result. Whether galactosemia NBS should be designed to detect DG and what should be done with those DG infants identified are issues that remain controversial (Fernhoff 2010). A study of 28 children with DG of mean age <4 years found no evidence of developmental delay (Ficicioglu et al 2008). In contrast, a study of elementary school records noted that children with DG were significantly over-represented in a cohort of students receiving special educational services (Powell et al 2009). Whether these apparently contradictory results reflect statistics of small numbers, or whether they indicate that DG children are at increased risk of developmental difficulties in midbut not early childhood, remains unclear. Communicated by: Bridget Wilcken

Gastrointestinal Health in Classic Galactosemia.

Classic galactosemia (CG) is an autosomal recessive disorder of galactose metabolism that affects approximately 1/50,000 live births in the USA. Following exposure to milk, which contains large quantities of galactose, affected infants may become seriously ill. Early identification by newborn screening with immediate dietary galactose restriction minimizes or prevents the potentially lethal acute symptoms of CG. However, more than half of individuals with CG still experience long-term complications including cognitive disability, behavioral problems, and speech impairment. Anecdotal reports have also suggested frequent gastrointestinal (GI) problems, but this outcome has not been systematically addressed. In this study we explored the prevalence of GI symptoms among 183 children and adults with CG (cases) and 190 controls. Cases reported 4.5 times more frequent constipation (95% CI 1.8-11.5) and 4.2 times more frequent nausea (95% CI 1.2-15.5) than controls. Cases with genotypes predicting residual GALT activity reported less frequent constipation than cases without predicted GALT activity but this difference was not statistically significant. Because the rigor of dietary galactose restriction varies among individuals with galactosemia, we further tested whether GI symptoms associated with diet in infancy. Though constipation was almost four times as common among cases reporting a more restrictive diet in infancy, this difference was not statistically significant. These data confirm that certain GI symptoms are more common in classic galactosemia compared to controls and suggest that future studies should investigate associations with residual GALT activity and dietary galactose restriction in early life.

Genetic and Transcriptomic Variation Linked to Neutrophil Granulocyte–Macrophage Colony-Stimulating Factor Signaling in Pediatric Crohn’s Disease

BACKGROUND Granulocyte-macrophage colony-stimulating factor auto-antibodies (GMAbs) suppress neutrophil-extrinsic GM-CSF signaling and increase risk for stricturing behavior in Crohns disease (CD). We aimed to define clinical, genomic, and functional associations with neutrophil-intrinsic GM-CSF signaling. METHODS Missense mutations in CSF2RA, CSF2RB, JAK2, STAT5A, and STAT5B were identified using whole-exome sequencing in 543 pediatric inflammatory bowel disease (IBD) patients. Neutrophil-intrinsic GM-CSF signaling was defined using the GM-CSF-induced STAT5 stimulation index (GMSI) in 180 pediatric IBD patients and 26 non-IBD controls. Reduced GM-CSF signaling (GMSI-Lo) was defined as the 20th percentile within the control group. Variation in neutrophil phospho-protein abundance, bacterial killing, and the global pattern of gene expression with the GMSI was determined. RESULTS We validated 18 potentially damaging missense mutations in CSF2RA and CSF2RB. CSF2RA A17G carriage increased from 10% in those with intact neutrophil GMSI to 32% in those with low GMSI (P = 0.02). The frequency of reduced Staphylococcus aureus killing increased from 17% in those with intact neutrophil GMSI to 35% in GMSI-Lo neutrophils (P = 0.043). Crohns disease neutrophils with low GMSI exhibited specific alterations in phospho-protein networks and genes regulating cytokine production, wound healing, and cell survival and proliferation. Stricturing behavior increased from 7% in patients with both low GMAb and intact GMSI to 64% in patients with both elevated GMAb and low GMSI (P < 0.0001). CONCLUSIONS Low/normal neutrophil-intrinsic GM-CSF signaling is associated with CSF2RA missense mutations, alterations in gene expression networks, and higher rates of disease complications in pediatric CD.

Genetic variants and pathways implicated in a pediatric inflammatory bowel disease cohort

In the United States, approximately 5% of individuals with inflammatory bowel disease (IBD) are younger than 20 years old. Studies of pediatric cohorts can provide unique insights into genetic architecture of IBD, which includes Crohn’s disease (CD) and ulcerative colitis (UC). Large genome-wide association studies have found more than 200 IBD-associated loci but explain a minority of disease variance for CD and UC. We sought to characterize the contribution of rare variants to disease development, comparing exome sequencing of 368 pediatric IBD patients to publicly available exome sequencing (dbGaP) and aggregate frequency data (ExAC). Using dbGaP data, we performed logistic regression for common variants and optimal unified association tests (SKAT-O) for rare, likely-deleterious variants. We further compared rare variants to ExAC counts with Fisher’s exact tests. We did pathway enrichment analysis on the most significant genes from each comparison. Many variants overlapped with known IBD-associated genes (e.g. NOD2). Rare variants were enriched in CD-associated loci (p = 0.009) and showed suggestive enrichment in neutrophil function genes (p = 0.05). Pathway enrichment implicated immune-related pathways, especially cell killing and apoptosis. Variants in extracellular matrix genes also emerged as an important theme in our analysis.