Computational and Mathematical Methods in Medicine

SY Pai, BR Logan, LM Griffith. N Engl J Med. 2014;371(5):434–446

To evaluate the outcome of hematopoietic stem cell transplantation (HSCT) in patients with severe combined immunodeficiency (SCID) treated in North America between 2000 and 2009 based on data collected by the Primary Immune Deficiency Treatment Consortium.

Two hundred forty infants with SCID treated with HSCT at 25 centers during this 10-year period.

This was a retrospective study based on data entry into defined forms through the Primary Immune Deficiency Treatment Consortium. Each patient entry was reviewed by 3 content experts and classified as eligible versus not eligible on the basis of defined criteria required to meet the diagnosis of SCID. Transplant information was provided …

Transplantation Outcomes for Severe Combined Immunodeficiency 2000–2009

Cholesterol is essential for neuronal physiology, both during development and in the adult life: as a major component of cell membranes and precursor of steroid hormones, it contributes to the regulation of ion permeability, cell shape, cell–cell interaction, and transmembrane signaling. Consistently, hereditary diseases with mutations in cholesterol-related genes result in impaired brain function during early life. In addition, defects in brain cholesterol metabolism may contribute to neurological syndromes, such as Alzheimer's disease (AD), Huntington's disease (HD), and Parkinson's disease (PD), and even to the cognitive deficits typical of the old age. In these cases, brain cholesterol defects may be secondary to disease-causing elements and contribute to the functional deficits by altering synaptic functions. In the first part of this review, we will describe hereditary and non-hereditary causes of cholesterol dyshomeostasis and the relationship to brain diseases. In the second part, we will focus on the mechanisms by which perturbation of cholesterol metabolism can affect synaptic function.

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Cholesterol in brain disease: sometimes determinant and frequently implicated

A Kwan, RS Abraham, R Currier. JAMA. 2014;312(7):729–738

To assess the results of a spectrum of state-based newborn screening programs using the T-cell receptor excision (TREC) testing approach to develop more accurate population-based incidence of severe combined immunodeficiency (SCID) and other conditions associated with T-cell lymphopenia and document the effectiveness of early intervention in those newborns found to have a significant immunologic abnormality.

Cumulative TREC newborn screening data were evaluated from 10 states plus the Navajo Nation involving ∼3 million newborns.

This was an epidemiologic and retrospective observational study based on states invited to submit SCID screening algorithms, test performance data, and deidentified clinical and laboratory information regarding infants screened and cases with nonnormal results. The data evaluated were collected from January 2008 through …

https://pediatrics.aappublications.org/content/pediatrics/136/Supplement_3/S275.full.pdf

Newborn Screening for Severe Combined Immunodeficiency in 11 Screening Programs in the United States

Human-genomics programs work together worldwide to speed the translation of genomic medicine to the clinic. Around the world, innovative genomic-medicine programs capitalize on singular capabilities arising from local health care systems, cultural or political milieus, and unusual selected risk alleles or disease burdens. Such individual efforts might benefit from the sharing of approaches and lessons learned in other locales. The U.S. National Human Genome Research Institute and the National Academy of Medicine recently brought together 25 of these groups to compare projects, to examine the current state of implementation and desired near-term capabilities, and to identify opportunities for collaboration that promote the responsible practice of genomic medicine. Efforts to coalesce these groups around concrete but compelling signature projects should accelerate the responsible implementation of genomic medicine in efforts to improve clinical care worldwide.

Global implementation of genomic medicine: We are not

Fatty acid oxidation disorders (FAODs) are inborn errors of metabolism due to disruption of either mitochondrial β-oxidation or the fatty acid transport using the carnitine transport pathway. The presentation of a FAOD will depend upon the specific disorder, but common elements may be seen, and ultimately require a similar treatment. Initial presentations of the FAODs in the neonatal period with severe symptoms include cardiomyopathy, while during infancy and childhood liver dysfunction and hypoketotic hypoglycemia are common. Episodic rhabdomyolysis is frequently the initial presentation during or after adolescence; although, these symptoms may develop at any age for most of the FAODs The treatment of all FAOD's include avoidance of fasting, aggressive treatment during illness, and supplementation of carnitine, if necessary. The long-chain FAODs differ by requiring a fat-restricted diet and supplementation of medium chain triglyceride oil and often docosahexaenoic acid (DHA)-an essential fatty acid, crucial for brain, visual, and immune functions and prevention of fat soluble vitamin deficiencies. The FAOD are a group of autosomal recessive disorders associated with significant morbidity and mortality, but early diagnosis on newborn screening (NBS) and early initiation of treatment are improving outcomes. There is a need for clinical studies including randomized, controlled, therapeutic trials to continue to evaluate current understanding and to implement future therapies.

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Fatty acid oxidation disorders.

Cholesterol has numerous quintessential functions in normal cell physiology, as well as in embryonic and postnatal development. It is a major component of cell membranes and myelin, and is a precursor of steroid hormones and bile acids. The development of the blood brain barrier likely around 12-18 weeks of human gestation makes the developing embryonic/fetal brain dependent on endogenous cholesterol synthesis. Known enzyme defects along the cholesterol biosynthetic pathway result in a host of neurodevelopmental and behavioral findings along with CNS structural anomalies. In this article, we review sterol synthesis disorders in the pre- and post-squalene pathway highlighting neurodevelopmental aspects that underlie the clinical presentations and course of Smith-Lemli-Opitz Syndrome (SLOS), mevalonic aciduria (MVA) or the milder version hyper-immunoglobulinemia D and periodic fever syndrome (HIDS), Antley-Bixler syndrome with genital anomalies and disordered steroidogenesis (ABS1), congenital hemidysplasia with icthyosiform nevus and limb defects (CHILD) syndrome, CK syndrome, sterol C4 methyl oxidase (SC4MOL) deficiency, X-linked dominant chondrodysplasia punctata 2(CDPX2)/ Conradi Hunermann syndrome, lathosterolosis and desmosterolosis, We also discuss current controversies and share thoughts on future directions in the field.

Sterol metabolism disorders and neurodevelopment-an update.

Amino acids serve as key building blocks and as an energy source for cell repair, survival, regeneration and growth. Each amino acid has an amino group, a carboxylic acid, and a unique carbon structure. Human utilize 21 different amino acids; most of these can be synthesized endogenously, but 9 are “essential” in that they must be ingested in the diet. In addition to their role as building blocks of protein, amino acids are key energy source (ketogenic, glucogenic or both), are building blocks of Kreb’s (aka TCA) cycle intermediates and other metabolites, and recycled as needed. A metabolic defect in the metabolism of tyrosine (homogentisic acid oxidase deficiency) historically defined Archibald Garrod as key architect in linking biochemistry, genetics and medicine and creation of the term ‘Inborn Error of Metabolism’ (IEM). The key concept of a single gene defect leading to a single enzyme dysfunction, leading to “intoxication” with a precursor in the metabolic pathway was vital to linking genetics and metabolic disorders and developing screening and treatment approaches as described in other chapters in this issue. Amino acid disorders also led to the evolution of the field of metabolic nutrition and offending amino acid restricted formula and foods. This review will discuss the more common disorders caused by inborn errors in amino acid metabolism.

Amino acid disorders

Glucose is the main energy fuel for the human brain. Maintenance of glucose homeostasis is therefore, crucial to meet cellular energy demands in both - normal physiological states and during stress or increased demands. Glucose is stored as glycogen primarily in the liver and skeletal muscle with a small amount stored in the brain. Liver glycogen primarily maintains blood glucose levels, while skeletal muscle glycogen is utilized during high-intensity exertion, and brain glycogen is an emergency cerebral energy source. Glycogen and glucose transform into one another through glycogen synthesis and degradation pathways. Thus, enzymatic defects along these pathways are associated with altered glucose metabolism and breakdown leading to hypoglycemia ± hepatomegaly and or liver disease in hepatic forms of glycogen storage disorder (GSD) and skeletal ± cardiac myopathy, depending on the site of the enzyme defects. Overall, defects in glycogen metabolism mainly present as GSDs and are a heterogenous group of inborn errors of carbohydrate metabolism. In this article we review the genetics, epidemiology, clinical and metabolic findings of various types of GSD, and glycolysis defects emphasizing current treatment and implications for future directions.

Glycogen metabolism and glycogen storage disorders

Inborn errors of metabolism (IEMs) are rare genetic or inherited disorders resulting from an enzyme defect in biochemical and metabolic pathways affecting proteins, fats, carbohydrates metabolism or impaired organelle function presenting as complicated medical conditions involving several human organ systems. They involve great complexity of the underlying pathophysiology, biochemical workup, and molecular analysis, and have complicated therapeutic options for management. Age of presentation can vary from infancy to adolescence with the more severe forms appearing in early childhood accompanied by significant morbidity and mortality. The understanding of these complex disorders requires special in-depth training, American Board of Medical Genetics and Genomics (ABMGG) certification and experience. Most primary care physicians (PCPs) are reluctant to deal with IEM due to unfamiliarity and rarity of such conditions compounded by prompt progression to crisis situations along with paucity of time involved in dealing with such complex disorders. While there are biochemical geneticists aka metabolic specialists’ expertise available, mostly in larger academic medical centers, with expertise to deal with these rare complex issues, their initial clinical presentation in most newborns, children, adolescents or adults including asymptomatic positive newborn screen (NBS), occur in the out-patient PCP settings. Therefore, it is important that PCPs’ comfort to recognize early signs and symptoms is important to initiate appropriate diagnostic and therapeutic interventions, and be able to make appropriate referrals. The following article reviews common IEM clinical presentations for a robust diagnostic differential and discuss evaluation and management approaches of patients with known or suspected IEM.

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Shibani Kanungo

Papers

Fatty acid oxidation disorders.

Sterol metabolism disorders and neurodevelopment-an update.

Amino acid disorders

Glycogen metabolism and glycogen storage disorders

Common metabolic disorder (inborn errors of metabolism) concerns in primary care practice.