Newborn Examination and PDH Complex Deficiency

Clinical chemistry case study Newborn examination Pyruvate dehydrogenase Complex Deficiency Neonatal hypoglycemia Newborn examination Purpose of the exam: Search for abnormalities and congenital malformations important to find any problems the baby may have and to allo...

Clinical chemistry case study Newborn examination Pyruvate dehydrogenase Complex Deficiency Neonatal hypoglycemia Newborn examination Purpose of the exam: Search for abnormalities and congenital malformations important to find any problems the baby may have and to allow each baby to be treated as soon as possible This part of the course will clarify the meaning of the documented newborn examination results in order for you to understand case studies related to congenital disorders What is a congenital malformation? A defect which is present at birth Some malformations may be easily seen, such as a cleft lip, or may affect internal organs and be more difficult to detect without sophisticated testing equipment, such as with certain heart defects Malformations can be cosmetic only, such as a dark birthmark on the face, or they can be life threatening such as a baby born with their intestines on the outside of the body What is a congenital malformation? Causes of birth defects: Genetic defects 10-15% Teratogen 7-10% Multi-factorial 30-35%: caused by more than one eitiologic factor Unknown ~50% Delivery Room Assessment: Apgar Score Taken at 1 and 5 minutes after birth Meant to identify the need for neonatal resuscitation General the baby’s color does the baby look ill or Perioral Cyanosis well Is the baby normally active Are there any obvious malformations? Acrocyanosis Jaundice Head Head circumference measurement Fontanelles: two soft spots on the top of the baby’s head The Anterior fontanelle is in the front, and is larger and more obvious than the posterior fontanelle Head The anterior fontanelle can be: Normal Raised or bulging- suggests infection, increased ICP or may be normal during crying Depressed or sunken- suggests dehydration Head Head size: Macrocephaly: the head is abnormally large may be normal or pathological, Pathologic megalencephaly macrocephaly may be due to (enlarged brain), hydrocephalus (water on the brain), cranial hyperostosis (bone overgrowth), and other conditions. Head Head size: Microcephaly: is a medical condition in which the brain does not develop properly resulting in a smaller than normal head Classified into congenital and postnatal Aonset. long list of chromosomal, genetic abnormalities and environmental factors are Face Is the baby’s face normal? Chin Mouth, lips & Palate Need to feel inside the mouth for a cleft palate Face Nose Are there 2 nostrils? Are both nostrils open? Choanal atresia (a blocked nostril) is checked by seeing if the infant can breathe with the left and then right nostril Eyes: clearoccluded (blocked) alternately and of equal size, with round pupils Cataracts: Eyes appear cloudy Face Ear Chest shape, symmetry, location of nipples, accessory nipples Accessory nipple (not significant ) Chest Are any of the following present? Chest indrawing Nasal flaring Tracheal tug These are signs of respiratory distress Chest Indrawing (Retractions) Abdomen Does the abdomen appear distended? liver and spleen Are any abnormal masses felt? Umbilical hernia: usually resolves on its Umbilicus Check the adequacy of the cord tie or clamp The umbilical cord usually has 3 blood vessels If only two are found, the baby is at risk of having other more serious congenital Umbilical abnormalities vessels: two arteries (A) and one vein (V). The vein is the largest of the 3  Abdominal Wall Malformations in which the internal organs remain outside the abdomen GASTROSCHESI OMPHALOCELE S The internal organs remain The umbilical cord is not in a sac involved Limbs Are the limbs, fingers and toes normal? Post axial polydactyly or extra “dangling” finger Normal  Limbs Brachydactyly Syndactyly or fused Camptodactyly: Congenital fingers digital flexion deformity Limbs Club feet Post axial polydactyly Syndactyly or fused toes Back & Spine Abnormalities along the midline or along the spine birthmarks, dimples, or tufts of hair along the spine These may be a sign of a more serious problem such as Spina Bifida Neural Tube Defects The neural tube is a narrow channel that folds and closes during the 3rd and 4th weeks of pregnancy to form the brain and spinal cord Incomplete closure of this tube results in several different birth defects Anencephaly Encephalocele Spina bifida Anencephaly Missing parts of the brain, skull, and scalp Babies with this condition often are born without the thinking part of the brain The remaining brain tissue is often exposed; that is, it is not covered by bone or skin Encephalocele A sac-like protrusion of the brain through an opening in the midline of the skull Spina Bifida Spina Bifida is a malformation where the bones around the spinal cord do not close all the way Sometimes, the skin is open as well, and the spinal cord is exposed Neurological Examination Means looking at muscles and nerves Does the infant have normal muscle tone? Is the infant too floppy or too stiff? Is the infant moving all limbs normally? Newborn Examination Sheet The following measurements will be taken during the exam and will be recorded: Weight (grams) Head Circumference (HC) (cm) Length (cm) Gestational age Gestational age is assessed based on physical and neurologic signs using new Ballard score The new Ballard score is commonly used to determine gestational age. Here’s how it works: Scores are given for 6 physical and 6 nerve and muscle development (neuromuscular) signs of maturity. The scores for each may range from -1 to 5. The scores are added together to determine the baby’s gestational age. The total score may range from -10 to 50. New Ballard score. ‫لالطال‬ ‫ع‬ New Ballard score. ‫لالطال‬ ‫ع‬ Gestational age After gestational age is determined, it is compared to birth weight to determine if intrauterine growth is appropriate AGA: Appropriate for Gestational Age 80% of all births, premature babies can be AGA SGA: Small for Gestational Age 10% of all births LGA: Large for Gestational Age 10% of all births Gestational age Large for Gestational age Usually seen with diabetic mothers May cause obstructed labour (dystocia) A premature baby can still be LGA! Small for Gestational age A premature, a term, or a post-term baby can all be Small for Gestational age! Chronic, low-grade stress in utero causes SGA Smoking, pre-eclampsia, malnutrition, infection, opiate drugs, placental Cases history, examination, and tests Identical twins with the fictitious names Ann and Elizabeth were born 6 weeks prematurely to a healthy 26-year-old mother whose pregnancy was uneventful. The family history was noteworthy for epilepsy in a paternal aunt, congenital deafness in another paternal aunt, and possible mental retardation in a maternal cousin. The twins’ sister was a healthy 3-year old girl with the same biological father. The birth weight was 3 pounds 9 ounces for Ann and 3 pounds 12 ounces for Elizabeth. Apgar scores 1 and 5 minutes after birth were 8 and 9 for both girls. Other than prematurity, neither child evidenced physical or laboratory abnormalities, and they were discharged home within 2 weeks (for Ann) and 3 weeks (for Elizabeth), both apparently in good health. Cases history, examination, and tests During the 3 months following their birth, both sisters sustained recurrent upper respiratory illnesses. These were more severe in Elizabeth, who required frequent hospitalizations. Physical examination of both infants during this period disclosed poor feeding habits, failure to thrive, floppiness, microcephaly, and delayed developmental milestones. They were below the fifth percentile for weight and height. These findings were more pronounced in Elizabeth, who also demonstrated ocular hypertelorism (abnormal increase in intraorbital distance) and pseudoathetosis (involuntary movements) of the lower face and hands. Cases history, examination, and tests Magnetic resonance imaging (MRI) of Elizabeth’s head revealed mild frontal atrophy and increased T2 signals in the periventricular and subcortical white matter. These signals are indicative of scarring or abnormalities in myelination. A pediatric neurologist diagnosed probable cerebral palsy in Elizabeth at age 1.5 years. Formal neurobehavioral evaluation of both children at age 3 years 10 months generated the results summarized in Table 7-1 Cases history, examination, and tests Further testing of Elizabeth showed profound hypotonia, electrophysiological evidence of peripheral neuropathy, normal somatosensory evoked potentials, and a normal electroencephalogram recorded during sleep. At age 2 years, the twins were placed on a diet comprised of approximately 60% total calories as (mainly saturated) long- chain fatty acids. They tolerated this “ketogenic diet” well, gained weight, and showed mild psychomotor improvement. At age 3 years 9 months, they enrolled in a controlled clinical trial of oral dichloroacetate (DCA), an activator of the pyruvate dehydrogenase complex (PDC). Cases history, examination, and tests Venous blood concentrations of lactate, obtained initially after an overnight fast and then 2 hours after a liquid meal containing 40% of calories as carbohydrate, were 1.2 mmol/L and 2.8 mmol/L, respectively, in Ann and 1.6 mmol/L and 5.7 mmol/L, respectively, in Elizabeth (normal venous blood lactate after fasting 0.4–1.0 mmol/L). The cerebrospinal fluid lactate concentration, obtained prior to carbohydrate ingestion, was approximately 5.6 mmol/L (normal approximately 1 mmol/L) in both children. Diagnosis The twins were referred subsequently to a metabolic specialist because of the suspicion of an inborn error of metabolism. Biochemical testing revealed each had metabolic acidosis that was more profound in Elizabeth. Serum levels of glucose and liver transaminases were normal. Urinary organic acids revealed modestly increased concentrations of lactate and ketone bodies. Blood samples and fibroblasts from skin biopsies from both girls were sent to an established diagnostic laboratory for genetic mitochondrial diseases. Tests of respiratory chain complex enzymatic activities were normal. Results of the measurement of PDC enzyme activity are summarized in Table 7-2. Diagnosis These data revealed severely reduced PDC activities in both freshly isolated peripheral blood lymphocytes and cultured fibroblasts in Ann and an even more striking reduction in enzyme activities in cells from Elizabeth. In each case, the defect in PDHC activity could be traced to a deficiency in the α-subunit of the first (E1) enzyme of the complex Pyruvate Dehydrogenase Complex PDC is a multienzyme complex (3 enzyme complex, E1,E2 and E3) located in the inner mitochondrial membrane. The enzyme provides a major source of acetyl CoA for the TCA cycle Under aerobic conditions, PDC catalyzes the rate-determining reaction for the oxidative removal of glucose, pyruvate, and lactate and helps sustain the tricarboxylic acid cycle by providing acetyl-CoA (Fig. 7-1). Reducing equivalents, in the form of NADH and FADH2, are generated by reactions catalyzed by the PDC and by various dehydrogenases in the tricarboxylic acid cycle and provide electrons to the respiratory chain for eventual reduction of molecular oxygen to water and synthesis of ATP. Figure 7-1. Pathways of fuel metabolism and oxidative phosphorylation. Pyruvate may be reduced to lactate in the cytoplasm or may be transported into the mitochondria for anabolic reactions, such as gluconeogenesis, or for oxidation to acetyl-CoA by the pyruvate dehydrogenase complex (PDC). Long-chain fatty acids are transported into mitochondria, where they undergo β-oxidation to ketone bodies (liver) or to acetyl-CoA (liver and other tissues). NADH, FADH2 are generated by reactions catalyzed by the PDC and TCA (Krebs) cycle and donate electrons (e−) that enter the respiratory chain (electron transport chain) where ATP and water are produced  Production of Acetyl CoA by PDC Pyruvate dehydrogenase is a heterotetrameric α-Ketoacid decarboxylase (decarboxylation = removal of carboxyl group in the form of CO2) that irreversibly oxidizes pyruvate to acetyl-CoA in the presence of thiamine pyrophosphate (TPP). As shown in the following reaction Required Coenzymes.: The pyruvate dehydrogenase complex contains five coenzymes that act as carriers or oxidants for the intermediates of the reaction shown in the previous figure. E1 requires thiamine pyrophosphate, E2 requires lipoic acid and CoA, and E3 requires FAD and NAD+.  PDC deficiency A deficiency in the E1 component of the pyruvate dehydrogenase complex is the most common biochemical cause of congenital lactic acidosis. This enzyme deficiency results in an inability to convert pyruvate to acetyl CoA, causing pyruvate to be shunted to lactic acid via lactate dehydrogenase. This causes particular problems for the brain, which relies on the TCA cycle for most of its energy, and is particularly sensitive to acidosis. Pyruvate dehydrogenase deficiency causes lactic acidosis. Symptoms are varied, and include developmental defects (especially of the brain and nervous system), muscular spasticity and early death. The E1 defect is X-linked, but because of the importance of the enzyme in the brain, it affects both males and females. Therefore, the defect is classified as X-linked dominant. Treatment There is no proven treatment for pyruvate dehydrogenase complex deficiency. Patients with PDC deficiency do not oxidize carbohydrates efficiently; hence, the pyruvate derived from glycolysis is more likely to be reduced in the cytoplasm to lactate. Indeed, carbohydrate-containing meals may exacerbate or precipitate life-threatening lactic acidosis in patients with severe PDC deficiency. This has led to the widespread use of high-fat diets that induce ketosis and provide an alternative source of acetyl-CoA, particularly for the CNS, which can utilize ketone bodies for energy metabolism. Case reports of a few children with PDC deficiency whose clinical course improved dramatically while following a high-fat diet are consistent with this postulate.  Treatment Very high doses of thiamine, sometimes exceeding 2 g/day, are reported to benefit some patients with PDC deficiency. TPP is an obligate cofactor for the E1 component of the PDC Dichloroacetate is the only drug that has been investigated in detail for the treatment of PDC deficiency. It inhibits PD Kinases and thus maintains E1 in its unphosphorylated, catalytically active form. DCA is a potent lactate-lowering agent, primarily by virtue of its effect on the PDC. The rationale for its use in PDC deficiency is based on the expectation it would stimulate residual enzyme activity in patients with either partial PDC activity or enzyme heterozygosity. In the latter case, activation of E1 by DCA in normal cells might help decrease lactate accumulation in adjacent defective cells and improve overall tissue or organ energy metabolism. (clinical trials) Clinical chemistry case study Neonatal Hypoglycemia and the Importance of Gluconeogenesis Case history and examination Female infant weighed 3.98 kg at birth to a 29-year-old mother after a 35-week pregnancy. The mother had type 1 diabetes since she was 15 years old. Her pregnancy had been complicated by multiple episodes of hyperglycemia and glycosuria. Her prenatal care was only episodic because her husband had been part of a layoff at work, and the family was without health insurance. On the day of delivery, The mother had a routine nonstress test (a test that records changes in fetal heart rate with fetal movement and uterine contractions using a machine called a cardiotocograph) because she noticed that her fetus had decreased movement over the preceding 2 days. A typical cardiotocography output for a woman not in labour. A: Fetal heartbeat; B: Indicator showing movements felt by mother (caused by pressing a button); C: Fetal movement; D: Uterine contractions Case history and examination The nonstress test showed a flat baseline heart rate without any variation, a finding suggesting that the fetus was at risk for asphyxia (lack of oxygen leading to an accumulation of lactic acid and carbon dioxide in the blood). Following the rupture of membranes, a blood sample taken from the fetal scalp revealed an acidotic pH of 6.9 (normal > 7.3). Because these findings were clear evidence of fetal distress, an immediate cesarean section was performed. The infant’s Apgar scores of 2 at 1 minute and 6 at 5 minutes suggested depression of neurological and cardiopulmonary function. The physicians resuscitated the infant, who was then taken to the neonatal intensive care unit. Case history and examination The infant had a normal pulse, respiratory rate, and rectal temperature. The infant’s head circumference and length were both normal for her gestational age; however, she was clearly macrosomic and plethoric (ruddy with an increased RBC mass, ‫ )محتقن بالدم‬and had a protuberant, firm abdomen and a disproportionate amount of adipose tissue around the upper body. The initial cardiac examination revealed no abnormalities. The pulses were symmetric but difficult to feel in all extremities. There were no other congenital anomalies. Infant condition progress and Lab results When the infant was aged 30 minutes, the hematocrit was 0.63 (normal is 0.45–0.62), and the serum glucose was 2.5 mmol/L (normal is 2.8–3.3 mmol/L). An IV line was established. The initial IV fluid was 10% dextrose in water and was administered at a rate of 10 mL/hour. Several minutes later, the infant’s blood glucose concentration was 1.2 mmol/L, and 10 mL of 25% dextrose in water was given via IV over a 5- minute period. Infant condition progress and Lab results The first arterial blood gas determination at 45 minutes of life revealed a pH of 7.18 (normal is 7.30–7.35), a PO2 of 6.3 kPa (normal is 6.7–9.3 kPa), a PCO2 of 6.1 kPa (normal is 4.7–6.0 kPa), and a bicarbonate concentration of 17 mmol/L (normal is 18–21 mmol/L), with a base excess of (−11 mmol/L) (metabolic acidosis and hypoxemia) A chest radiographic film showed that the lungs were clear, and the heart was large. One hour and 10 minutes after birth, the infant’s blood sugar was 21.0 mmol/L (after infusion of 10 mL of 25% dextrose noted above). Infant condition progress and Lab results About 45 minutes later, the blood sugar was 1.8 mmol/L, and 8 mL of 10% dextrose was given IV over 5 minutes. The IV infusion was changed to 12.5% dextrose in water at a rate of 13 mL/h. Within 10 to 15 minutes, the serum glucose level had fallen to between 0 and 1.4 mmol/L, and an additional 4 mL of 12.5% dextrose was given IV. A catheter was then inserted into the umbilical vein to lie in the lower part of the right atrium, and an infusion of 15% dextrose was begun. By 5 hours of age, this infant was receiving glucose at a rate of 13.5 mg/kg/min. The blood glucose concentration continued to be less than 1.1 mmol/L, and the infant was given 15 mg of hydrocortisone every 6 hours. Infant condition progress and Lab results Echocardiography showed decreased left ventricular contractility and hypertrophy of the ventricular septum but no other structural abnormalities. These findings were consistent with the cardiomyopathy often seen in infants of diabetic mothers. By 12 hours of age, the infant had seizure activity that included rhythmic movement of both upper extremities, hiccupping, and repetitive chewing movements. An electroencephalogram was grossly abnormal, showing paroxysmal bursts of activity (seizures) and periods of suppression. Phenobarbital was given to alleviate the seizure activity. Infant condition progress and Lab results Eventually, the infant’s need for hydrocortisone began to decrease so that by the ninth day of life she no longer required steroids, and she maintained serum glucose concentrations above 2.8 mmol/L with a glucose infusion of less than 7 mg/kg per minute. Subsequently, glucose control was no longer difficult, and no further medications were given for this problem. Diagnosis This case exemplifies many of the problems classically associated with infants born to diabetic mothers. Inadequate maternal glucose control during pregnancy generates potential metabolic difficulties in the infant. The size of this infant at birth (nearly 4 kg in a preterm infant), however, categorizes her as large for gestational age, a finding characteristic of affected infants of diabetic mothers. This infant is therefore likely to have the other manifestations associated with this pathophysiology. Indeed, many characteristics of this infant are typical for a child born to a mother with inadequately treated diabetes mellitus. Diagnosis Specifically, the macrosomia (large organs), round facies, plethora, and overall weight, length, and head circumference are all consistent with poorly controlled maternal diabetes mellitus that has significantly affected fetal growth and metabolism. As the end of gestation approaches, the fetus of a diabetic mother is more likely to be poorly oxygenated in utero. The markedly decreased scalp pH and low Apgar scores are convincing evidence that this infant’s supply of oxygen was insufficient to meet her need. Diagnosis The etiology of the hypoxemia is not always apparent at the time of birth. Any mechanical disruption of the fetal-placental circulation (e.g., abruption or separation, placenta previa, or cord accidents) could compromise fetal oxygen supply, as could a fetal infection. In the present case, however, there was no evidence of such problems. Consequently, it seems more likely that the fetus exhibited the chronic oxygen deficit that occurs in infants of diabetic mothers and becomes more severe as the pregnancy progresses. Diagnosis Hypoglycemia beginning soon after birth is typical for infants of diabetic mothers. Indeed, what happened with this infant should have expected because the infant was so conspicuously affected by her mother’s diabetes. Fortunately, the severity of the present case, including the need for glucocorticoids, has become rare since the advent of more sophisticated maternal care during pregnancy. Seizures are an unfortunate and serious complication of hypoglycemia, but it is not possible to determine whether the lack of oxygen during prenatal life, the hypoglycemia, or a combination of both is responsible for the infant’s brain damage. Neonatal Hypoglycemia There is no agreed definition of hypoglycaemia in the newborn. Many babies tolerate low blood glucose levels in the first few days of life, as they are able to utilise lactate and ketones as energy stores. (Full-term neonates will frequently have a transient hypoglycemia with blood glucose measurements 1.7-2.2 mmol/L and spontaneously recover.) Recent evidence suggests that blood glucose levels above 2.6 mmol/L are desirable for optimal neurodevelopmental outcome, although during the first 24 h after birth many asymptomatic infants transiently have blood glucose levels below this level. There is good evidence that prolonged, symptomatic hypoglycaemia can cause permanent neurological disability. Causes With hyperinsulinism Without hyperinsulinism Transient hyperinsulinism Transient hypoglycemia: Infants of diabetic mothers and IUGR, birth asphyxia, infants with Rh hemolytic polycythemia, cardiac disease, disease CNS disease, sepsis, maternal use of propranolol, oral hypoglycemic agents, or narcotic addiction Protracted hyperinsulinism: Protracted hypoglycemia: Infants who have Beckwith- Neonatal hypopituitarism, Defects Wiedemann syndrome, islet cell in carbohydrate (glycogen storage adenomas, and functional disease type I, glycogen synthetase hyperinsulinism. deficiency, fructose- l ,6- diphosphatase deficiency, fructose intolerance, and galactosemia) and/or amino acid metabolism (methylmalonic acidemia, tyrosinosis, propionic acidemia, and maple syrup urine disease). Pathogenesis of neonatal hypoglycemia in Infants of Diabetic Mothers Uncontrolled maternal glycemia causes neonatal hypoglycemia as well as transient hyperinsulinemia. In utero, maternal hyperglycemia increases placental glucose transport and results in fetal hyperglycemia, which stimulates fetal pancreatic insulin production. After delivery, maternal glucose supply ceases even though newborn insulin production continues and results in hypoglycemia. Hypoglycemia may continue for 24–72 h until insulin secretion returns to normal. Newborn glucose levels fall to a low point in the first 1–2 h of life and then increased and stabilize gradually. Pathogenesis of neonatal hypoglycemia in Infants of Diabetic Mothers Over the first hours of life, such infants persist in having higher than normal insulin concentrations and lower than normal glycogen concentrations. In addition, the concentrations of other counterregulatory hormones, such as glucagon, and epinephrine remain low. This particular hormonal profile will seriously inhibit glycogenolysis, thereby decreasing the rate of glucose release from the liver. Unfortunately, the endocrine environment of the infant whose mother is diabetic also suppresses the production of glucose from its only other major potential source: amino acids. Pathogenesis of neonatal hypoglycemia in Infants of Diabetic Mothers High insulin levels in both fetal and neonatal life inhibit protein breakdown, thereby decreasing the availability of amino acids from endogenous sources for potential use as gluconeogenic substrates. In addition, the marked increase that normally occurs in the activities of two important rate- controlling gluconeogenic enzymes, cytosolic PEP carboxykinase and glucose 6-phosphatase, is suppressed owing to the higher insulin and lower counterregulatory hormone concentrations of infants born to diabetic mothers. The combined effect of the decreased capacity for glycogenolysis and gluconeogenesis in infants of diabetic mothers is a marked decrease in the ability of the newborn to release glucose from the liver into the blood.  Pathogenesis of neonatal hypoglycemia in Infants of Diabetic Mothers Such a decrease in glucose production would have less impact if other metabolic fuels could be mobilized and used. As noted, the fetus whose mother has diabetes has greatly increased fat stores. In these infants, the amount of fat present is theoretically sufficient to supply adequate metabolic substrate for weeks, but the high insulin concentrations markedly inhibit lipolysis. As a consequence, tissues like heart and skeletal muscle, which are otherwise capable of using fatty acids to satisfy metabolic needs, are compelled to continue oxidizing glucose. The infant of a diabetic mother, therefore, in the face of impaired glucose production, has a higher than normal rate of glucose consumption. This circumstance precipitates a marked fall in the blood glucose concentration of the neonate. Treatment Hypoglycemia can usually be prevented by early and frequent milk feeding. In infants at increased risk of hypoglycemia, blood glucose is regularly monitored at the bedside. If an asymptomatic infant has two low glucose values (i.e. below 2.6 mmol/L) in spite of adequate feeding or one very low value (2.6 mmol/L. The concentration of the intravenous dextrose may need to be increased from 10% to 15% or even 20%. Abnormal blood glucose results should be confirmed in the laboratory. Treatment High concentration intravenous infusions of glucose should be given via a central venous catheter to avoid extravasation into the tissues, which may cause skin necrosis and reactive hypoglycaemia. If there is difficulty or delay in starting the infusion, or a satisfactory response is not achieved, glucagon or hydrocortisone can be given.