Clinical Focus

  • Perinatal Genetics
  • Genetics of Recurrent Pregnancy Loss & Infertility
  • Differences of Sexual Development
  • Dysmorphology
  • Diagnostic Tools & Methodology
  • Clinical Genetics

Academic Appointments

Administrative Appointments

  • Associate Director, Perinatal Genetics (2017 - Present)
  • Clerkship Director, Division of Medical Genetics (2018 - Present)

Boards, Advisory Committees, Professional Organizations

  • Member, American Society of Human Genetics (2014 - Present)
  • Membership Committee, American College of Medical Genetics and Genomics (2015 - Present)

Professional Education

  • Fellowship:University of Washington Medical Genetics Fellowship (2017) WA
  • Board Certification: Clinical Genetics, American Board of Medical Genetics and Genomics (2017)
  • Residency:University of Washington Medical Center (2016) WA
  • Residency:University of Texas at Austin (2014) TX
  • Medical Education:University of Iowa Carver College of Medicine (2012) IA

All Publications

  • Factor VIII and vWF deficiency in STT3A-CDG. Journal of inherited metabolic disease Chang, I. J., Byers, H. M., Ng, B. G., Merritt, J. L., Gilmore, R., Shrimal, S., Wei, W., Zhang, Y., Blair, A. B., Freeze, H. H., Zhang, B., Lam, C. 2018


    STT3A-CDG (OMIM# 615596) is an autosomal recessive N-linked glycosylation disorder characterized by seizures, developmental delay, intellectual disability, and a type I carbohydrate deficient transferrin pattern. All previously reported cases (n=6) have been attributed to a homozygous pathogenic missense variant c.1877C>T (p.Val626Ala) in STT3A. We describe a patient with a novel homozygous likely pathogenic missense variant c.1079A>C (p.Tyr360Ser) who presents with chronically low Factor VIII (FVIII) and von Willebrand Factor (vWF) levels and activities in addition to the previously reported symptoms of developmental delay and seizures. VWF in our patient's plasma is present in a mildly hypoglycosylated form. FVIII antigen levels were too low to quantify in our patient. Functional studies with STT3A-/- HEK293 cells showed severely reduced FVIII antigen and activity levels in conditioned media <10% expected, but normal intracellular levels. We also show decreased glycosylation of STT3A-specific acceptors in fibroblasts from our patient, providing a mechanistic explanation for how STT3A deficiency leads to a severe defect in FVIII secretion. Our results suggest that certain STT3A-dependent N-glycans are required for efficient FVIII secretion, and the decreased FVIII level in our patient is a combined effect of both severely impaired FVIII secretion and lower plasma VWF level. Our report expands both the genotype and phenotype of STT3A-CDG; demonstrating, as in most types of CDG, that there are multiple disease-causing variants in STT3A.

    View details for DOI 10.1002/jimd.12021

    View details for PubMedID 30701557

  • Discordant sex between fetal screening and postnatal phenotype requires evaluation. Journal of perinatology : official journal of the California Perinatal Association Byers, H. M., Neufeld-Kaiser, W., Chang, E. Y., Tsuchiya, K., Oehler, E. S., Adam, M. P. 2018


    OBJECTIVE: Non-invasive prenatal screening (NIPS) utilizes circulating cell-free DNA (cfDNA) to screen for fetal genetic abnormalities. NIPS is the first widely-available prenatal screen to assess genotypic sex. Most pediatricians have limited familiarity with NIPS technology and potential etiologies of discordant results. Increased familiarity may provide diagnostic insight and improve clinical care.STUDY DESIGN: We reviewed all patients with discordant genotypic fetal sex assessed by cfDNA and neonatal phenotypic sex referred to our medical center.RESULT: Four infants with discordant cfDNA result and phenotypic sex were identified. Etiologies include vanishing twin syndrome, difference of sexual development, sex chromosome aneuploidy and maternal chimerism.CONCLUSIONS: We present four cases illustrating potential etiologies of discordant cfDNA result and postnatal phenotypic sex. Unanticipated cfDNA results offer the perinatologist a unique opportunity for early diagnosis and targeted treatment of various conditions, many of which may not have otherwise been detected in the perinatal period.

    View details for DOI 10.1038/s41372-018-0278-5

    View details for PubMedID 30459335

  • Increasing the Participation of Pregnant Women in Clinical Trials. JAMA Heyrana, K., Byers, H. M., Stratton, P. 2018

    View details for DOI 10.1001/jama.2018.17716

    View details for PubMedID 30422300

  • Expanding the phenotype of congenital central hypoventilation syndrome impacts management decisions. American journal of medical genetics. Part A Byers, H. M., Chen, M., Gelfand, A. S., Ong, B., Jendras, M., Glass, I. A. 2018


    Congenital central hypoventilation syndrome (CCHS) is a neurocristopathy caused by pathogenic heterozygous variants in the gene paired-like homeobox 2b (PHOX2B). It is characterized by severe infantile alveolar hypoventilation. Individuals may also have diffuse autonomic nervous system dysfunction, Hirschsprung disease and neural crest tumors. We report three individuals with CCHS due to an 8-base pair duplication in PHOX2B; c.691_698dupGGCCCGGG (p.Gly234Alafs*78) with a predominant enteral and neural crest phenotype and a relatively mild respiratory phenotype. The attenuated respiratory phenotype reported here and elsewhere suggests an emergent genotype:phenotype correlation which challenges the current paradigm of invoking mechanical ventilation for all infants diagnosed with CCHS. Best treatment requires careful clinical judgment and ideally the assistance of a care team with expertise in CCHS.

    View details for DOI 10.1002/ajmg.a.38726

    View details for PubMedID 29696799

  • Acute liver failure in neonates with undiagnosed hereditary fructose intolerance due to exposure from widely available infant formulas MOLECULAR GENETICS AND METABOLISM Li, H., Byers, H. M., Diaz-Kuan, A., Vos, M. B., Hall, P. L., Tortorelli, S., Singh, R., Wallenstein, M. B., Allain, M., Dimmock, D. P., Farrell, R. M., McCandless, S., Gambello, M. J. 2018; 123 (4): 428–32


    Hereditary fructose intolerance (HFI) is an autosomal recessive disorder caused by aldolase B (ALDOB) deficiency resulting in an inability to metabolize fructose. The toxic accumulation of intermediate fructose-1-phosphate causes multiple metabolic disturbances, including postprandial hypoglycemia, lactic acidosis, electrolyte disturbance, and liver/kidney dysfunction. The clinical presentation varies depending on the age of exposure and the load of fructose. Some common infant formulas contain fructose in various forms, such as sucrose, a disaccharide of fructose and glucose. Exposure to formula containing fructogenic compounds is an important, but often overlooked trigger for severe metabolic disturbances in HFI. Here we report four neonates with undiagnosed HFI, all caused by the common, homozygous mutation c.448G>C (p.A150P) in ALDOB, who developed life-threatening acute liver failure due to fructose-containing formulas. These cases underscore the importance of dietary history and consideration of HFI in cases of neonatal or infantile acute liver failure for prompt diagnosis and treatment of HFI.

    View details for DOI 10.1016/j.ymgme.2018.02.016

    View details for Web of Science ID 000430037100003

    View details for PubMedID 29510902

  • Postmortem Somatic Sequencing of Tumors From Patients With Suspected Lynch Syndrome Has Clinical Utility for Surviving Relatives JCO Precision Oncology Byers, H. M., Jacobson, A., McFaddin, A. S., Ussakli, C. H., Newlin, A., Stanich, P. S., More, S., Hamblett, A., Tait, J., Shirts, B., Pritchard, C. C., Konnick, E. Q., Lockwood, C. M. 2018; 2 (1): 1-7

    View details for DOI 10.1200/PO.18.00108

  • Unexpected ethical dilemmas in sex assignment in 46,XY DSD due to 5-alpha reductase type 2 deficiency AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS Byers, H. M., Mohnach, L. H., Fechner, P. Y., Chen, M., Thomas, I. H., Ramsdell, L. A., Shnorhavorian, M., McCauley, E. A., Oelschlager, A., Park, J. M., Sandberg, D. E., Adam, M. P., Keegan, C. E. 2017; 175 (2): 260–67


    Sex assignment at birth remains one of the most clinically challenging and controversial topics in 46,XY disorders of sexual development (DSD). This is particularly challenging in deficiency of 5-alpha reductase type 2 given that external genitalia are typically undervirilized at birth but typically virilize at puberty to a variable degree. Historically, most individuals with 5-alpha reductase deficiency were raised females. However, reports that over half of patients who underwent a virilizing puberty adopted an adult male gender identity have challenged this practice. Consensus guidelines on assignment of sex of rearing at birth are equivocal or favor male assignment in the most virilized cases. While a male sex of rearing assignment may avoid lifelong hormonal therapy and/or allow the potential for fertility, female sex assignment may be more consistent with external anatomy in the most severely undervirilized cases. Herein, we describe five patients with 46,XY DSD due 5-alpha-reductase type 2 deficiency, all with a severe phenotype. An inter-disciplinary DSD medical team at one of two academic centers evaluated each patient. This case series illustrates the complicated decision-making process of assignment of sex of rearing at birth in 5-alpha reductase type 2 deficiency and the challenges that arise when the interests of the child, parental wishes, recommendations of the medical team, and state law collide.

    View details for DOI 10.1002/ajmg.c.31560

    View details for Web of Science ID 000403697900003

    View details for PubMedID 28544750

    View details for PubMedCentralID PMC5489130