Pilot study of mitochondrial bioenergetics in subjects with acute porphyrias.

BACKGROUND AND AIMS: The acute porphyrias are characterized by defects in heme synthesis, particularly in the liver. In some affected patients, there occurs a critical deficiency in a regulatory heme pool within hepatocytes that leads to up-regulation of 5-aminolevulinic acid [ALA] synthase-1, which is the first and normally rate-controlling enzyme in the pathway. In earlier work, we described defects in mitochondrial functions in cultured skin fibroblasts from patients with acute intermittent porphyria [AIP]. Others described defects in livers of murine models of AIP. Here, we explored mitochondrial energetics in peripheral blood mononuclear cells [PBMCs] and platelets in persons with AIP and hereditary coproporphyria [HCP]. Our hypotheses were that there are deficits in bioenergetic capacity in acute porphyrias and that subjects with more severe acute porphyria have more pronounced reductions in mitochondrial oxygen consumption rates [OCR]. METHODS: We studied 17 subjects with acute hepatic porphyrias, 14 with classical AIP, one with severe AIP due to homozygous deficiency of hydroxymethylbilane synthase [HMBS], 2 with HCP, and 5 non-porphyric controls. We collected peripheral blood, isolated PBMCs, which we assayed either immediately or after frozen storage [80C] for up to 14 days. Using Seahorse XF-24-3, we measured OCR in the presence of glucose + pyruvate under basal condition, and after additions of oligomycin, carbonylcyanide p-trifluoromethoxyphenylhydrazone [FCCP], and antimycin+rotenone. RESULTS: Most subjects [13/17, 76%] were female. Subjects with moderate/severe symptoms associated with acute porphyria had significantly lower basal and maximal-OCR than those with no/mild symptoms who were the same as controls. We observed significant inverse correlation between urinary porphobilinogen [PBG] excretion and OCR. The subject with homozygous AIP had a much lower-OCR than his asymptomatic parents. SUMMARY/CONCLUSIONS: Results support the hypothesis that active acute hepatic porphyria is characterized by a deficiency in mitochondrial function that is detectable in PBMCs, suggesting that limitations in electron transport and ATP production exist in such individuals.

Pathogenesis and clinical features of the acute hepatic porphyrias (AHPs).

The acute hepatic porphyrias include four disorders: acute intermittent porphyria [AIP], hereditary coproporphyria [HCP], variegate porphyria [VP], and the rare porphyria due to severe deficiency of ALA dehydratase [ADP]. In the USA, AIP is the most severe and most often symptomatic. AIP, HCP, and VP are due to autosomal dominant genetic abnormalities, in which missense, nonsense, or other mutations of genes of normal hepatic heme biosynthesis, in concert with other environmental, nutritional, hormonal and genetic factors, may lead to a critical deficiency of heme, the end-product of the pathway, in a small but critical 'regulatory pool' within hepatocytes. This deficiency leads to de-repression of the first and normally rate-controlling enzyme of the heme synthetic pathway, delta- or 5-aminolevulinic acid [ALA] synthase-1, and thus to marked up-regulation of this key enzyme and to marked hepatic overproduction of ALA. In addition, except for ADP, there is marked overproduction as well of porphobilinogen [PBG], the intermediate immediately downstream of ALA in the synthetic chain, and, especially in HCP and VP, also porphyrinogens and porphyrins farther down the pathway. The major clinical features of the acute porphyrias are attacks of severe neuropathic-type pain. Pain is felt first and foremost in the abdomen but may also occur in the back, chest, and extremities. Attacks are more common in women than in men [ratio of about 4:1], often accompanied by nausea, vomiting, constipation, tachycardia, and arterial hypertension. Hyponatremia may also occur. Some patients also describe chronic symptoms of pain, anxiety, insomnia, and others.

Controlled trial of transfusions for silent cerebral infarcts in sickle cell anemia.

BACKGROUND: Silent cerebral infarcts are the most common neurologic injury in children with sickle cell anemia and are associated with the recurrence of an infarct (stroke or silent cerebral infarct). We tested the hypothesis that the incidence of the recurrence of an infarct would be lower among children who underwent regular blood-transfusion therapy than among those who received standard care. METHODS: In this randomized, single-blind clinical trial, we randomly assigned children with sickle cell anemia to receive regular blood transfusions (transfusion group) or standard care (observation group). Participants were between 5 and 15 years of age, with no history of stroke and with one or more silent cerebral infarcts on magnetic resonance imaging and a neurologic examination showing no abnormalities corresponding to these lesions. The primary end point was the recurrence of an infarct, defined as a stroke or a new or enlarged silent cerebral infarct. RESULTS: A total of 196 children (mean age, 10 years) were randomly assigned to the observation or transfusion group and were followed for a median of 3 years. In the transfusion group, 6 of 99 children (6%) had an end-point event (1 had a stroke, and 5 had new or enlarged silent cerebral infarcts). In the observation group, 14 of 97 children (14%) had an end-point event (7 had strokes, and 7 had new or enlarged silent cerebral infarcts). The incidence of the primary end point in the transfusion and observation groups was 2.0 and 4.8 events, respectively, per 100 years at risk, corresponding to an incidence rate ratio of 0.41 (95% confidence interval, 0.12 to 0.99; P=0.04). CONCLUSIONS: Regular blood-transfusion therapy significantly reduced the incidence of the recurrence of cerebral infarct in children with sickle cell anemia. (Funded by the National Institute of Neurological Disorders and Stroke and others; Silent Cerebral Infarct Multi-Center Clinical Trial ClinicalTrials.gov number, NCT00072761, and Current Controlled Trials number, ISRCTN52713285.).

Two new hemoglobin variants: Hb Tallahassee [α3(A1)Ser→Tyr; HBA2: c.11C>A] and Hb madison-NC [ß119(GH2)Gly→Ser; HBB: c.358G>A].

Of the 1570 reported hemoglobin (Hb) variants detected to date, 390 are α2-globin chain (some variants have yet to be identified by DNA analyses and are therefore presumed) and 827 are the result of mutations of the ß-globin chain. Due to their location on the Hb structure, only a minority of these variants result in a clinical phenotype; most are silent and are detected during routine surveillance, are found incidentally during other disease-related investigations or following newborn screening programs. In this report we discuss phenotype/genotype and molecular characteristics of two new Hb variants, both of which were clinically silent. One is an α2-globin chain variant located at codon 3 [α3(A1)Ser→Tyr; HBA2: c.11C > A] named Hb Tallahassee and the other is a ß-globin chain variant located at codon 119 [ß119(GH2)Gly→Ser; HBB: c.358G > A] called Hb Madison-NC.

Neonatal ascending aortic thrombus: successful medical treatment.

Neonatal aortic thrombosis is a potentially life-threatening condition with significant morbidity and mortality if undiagnosed and untreated. The most common location of arterial thrombosis in neonates is in the abdominal aorta and is associated with umbilical artery catheterisation. There are only a few previous reports of thrombosis in the ascending aorta. We describe a case of ascending aortic thrombosis in a neonate who underwent successful thrombolytic therapy.

Thalassemia-like phenotype in a novel complex hemoglobinopathy with α, ß, δ globin chain abnormalities.

The occurrence of multiple abnormalities of α, ß, δ, and γ globin genes may lead to unusual and complex phenotypes when they arise simultaneously in the same individual. Here, we report the findings of an African American boy who coinherited 3 heterozygous globin gene abnormalities: the unstable ß-globin chain variant; hemoglobin (Hb) Showa-Yakushiji [ß110(G12) Leu→Pro], the δ-globin chain variant; HbB2 [δ16(A13) Gly→Arg] and α-thalassemia (α-thal); (α-/αα). Hb Showa-Yakushiji had been previously described in Japanese, Indian, and European populations. We report its first occurrence in a child of African ancestry who presented with anemia not responsive to iron and an incomplete ß-thalassemia minor phenotype. Although the clinical and laboratory features of Hb Showa-Yakushiji mimic those of a ß-thalassemia, the coinheritance of the δ-globin chain variant Hb B2 suppressed the relative increase in Hb A2 usually observed in heterozygotes for the Hb Showa-Yakushiji mutation. Protein-based methods detected only a trace amount of HbB2 and failed to reveal presence of Hb Showa-Yakushiji and α-thal. The latter were only identified through DNA analyses. The diagnostic difficulties, molecular characteristics, and genotype/phenotype correlations of this novel complex hemoglobinopathy syndrome are reviewed.

Prevalence of iron deficiency in children with Down syndrome.

OBJECTIVES: To determine the prevalence of iron deficiency (ID) and iron deficiency anemia (IDA) in a sample of children with Down syndrome (DS) and to evaluate the effect of macrocytosis on the diagnosis of ID/IDA in these children. STUDY DESIGN: Children with DS ≥ 12 months of age who were followed at the Duke University Medical Center Comprehensive DS Clinic from December 2004 to March 2007 were screened for ID/IDA with a complete blood count, reticulocyte count, iron panel, and erythrocytic protoporphyrins. RESULTS: A total of 114 children were enrolled, with a median age of 4.7 years. ID was identified in 12 subjects (10%), and IDA was identified in 3 subjects (3%). ID/IDA would not have been accurately diagnosed in 13 of 15 subjects (86%) if red blood cell (RBC) indices alone had been used for screening. Abnormal RBC indices with low transferrin saturation were 100% sensitive for ID/ IDA screening. CONCLUSIONS: Prevalence of ID/IDA in children with DS was comparable with that in the general pediatric population. Macrocytosis had implications for screening of ID/IDA with only RBC indices. We suggest ID/IDA screening in DS children be done with a laboratory panel at least including complete blood count, reticulocyte count, transferrin saturation, and serum ferritin.

A pilot study of hydroxyurea to prevent chronic organ damage in young children with sickle cell anemia.

BACKGROUND: Hydroxyurea improves laboratory parameters and prevents acute clinical complications of sickle cell anemia (SCA) in children and adults, but its effects on organ function remain incompletely defined. METHODS: To assess the safety and efficacy of hydroxyurea in young children with SCA and to prospectively assess kidney and brain function, 14 young children (mean age 35 months) received hydroxyurea at a mean maximum tolerated dose (MTD) of 28 mg/kg/day. RESULTS: After a mean of 25 months, expected laboratory effects included significant increases in hemoglobin, MCV and %HbF along with significant decreases in reticulocytes, absolute neutrophil count, and bilirubin. There was no significant increase in glomerular filtration rate by DTPA clearance or Schwartz estimate. Mean transcranial Doppler (TCD) velocity changes were -25.6 cm/sec (P < 0.01) and -26.8 cm/sec (P < 0.05) in the right and left MCA vessels, respectively. At study exit, no child had conditional or abnormal TCD values, and none developed brain ischemic lesions or vasculopathy progression by MRI/MRA. Growth and neurocognitive scores were preserved and Impact-on-Family scores improved. CONCLUSIONS: These pilot data indicate hydroxyurea at MTD is well-tolerated by both children and families, and may prevent chronic organ damage in young children with SCA.

Thrombophilia screening in asymptomatic children.

Children with a family history of thrombophilia and/or thrombosis are often referred to pediatric thrombosis centers for evaluation. This article reviews the risks and benefits of thrombophilia testing in this unique population. The article also reviews an approach to testing including a step-wise evaluation and involvement of a genetic counselor.

Clinical manifestations of hematologic and oncologic disorders in patients with Down syndrome.

Hematologic abnormalities are common in individuals with Down syndrome (DS). Increased erythrocyte mean corpuscular volume (MCV) is frequently found among DS infants and remains elevated throughout life in two-thirds of patients, making interpretation of red cell indices for diagnosis of nutritional anemias or bone marrow failure disorders more challenging. Transient myeloproliferative disorder (TMD) associated with pancytopenia, hepatosplenomegaly, and circulating immature WBCs, is found almost exclusively in DS infants with an incidence of approximately 10%. In most cases, TMD regresses spontaneously within the first 3 months of life, but in some children, it can be life threatening or even fatal. Despite the high rate of spontaneous regression, TMD can be a preleukemic disorder in 20-30% of children with DS. The types of malignancy, response to therapy, and clinical outcome in children with DS are also unique. There is an increased risk of leukemia with an equal incidence of lymphoid and myeloid leukemia. Acute megakaryocytic leukemia (AMKL) subtype is the most common form of acute myeloid leukemia (AML) in this setting, and is uncommon in children without DS. Somatic mutations of the gene encoding the hematopoetic growth factor GATA1 have been shown to be specific for TMD and AMKL in children with DS. Myelodysplastic syndrome can precede AML. Children with DS and leukemia are more sensitive to some chemotherapeutic agents such as methotrexate than other children which requires careful monitoring for toxicity. Although the risk for leukemia is higher in individuals with DS, these patients have a lower risk of developing solid tumors, with the exception of germ cell tumors, and perhaps retinoblastoma and lymphoma.