Iron deficiency in children with mitochondrial disease

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Metab Brain Dis (2010) 25:185–189 DOI 10.1007/s11011-010-9196-8

ORIGINAL PAPER

Iron deficiency in children with mitochondrial disease Hye Eun Kwon & Jung Hun Lee & Young Mock Lee & Hoon Chul Kang & Joon Soo Lee & Heung Dong Kim

Received: 11 July 2009 / Accepted: 27 August 2009 / Published online: 28 April 2010 # Springer Science+Business Media, LLC 2010

Abstract Mitochondrial disease is an energy metabolic disorder with various organ involvement. Iron is widely known to be one of the most important nutriments required for normal brain development and several essential metabolic functions. We retrospectively studied the laboratory data on iron deficiency (ID) in 69 children with mitochondrial respiratory chain complex (MRC) defects by biochemical enzyme assay using muscle tissue. We analyzed the differences between groups of mitochondrial disease based on the presence of ID. ID has higher prevalence in children with mitochondrial disease than in the normal population. There were 6 (9%) patients with low hemoglobin, 12 (17%) with low serum ferrtin, and 22 (32%) with low transferrin saturation levels among children with MRC defects. In comparisons between the ID and the non-ID group of MRC-defect patients, the frequency of MRC I defect was significantly higher in the ID group while that of MRC IV defect was higher in the non-ID group. Abnormal brain magnetic resonance imaging (MRI) findings were more frequently detected in the ID group. The incidence of failure to thrive and gastrointestinal symptoms were significantly higher in the ID group. Early diagnosis and proper treatment of ID are recommended. Especially in cases with risk factors such as failure to thrive or gastrointestinal manifestation, active evaluation of ID should be encouraged.

H. E. Kwon : J. H. Lee : Y. M. Lee (*) : H. C. Kang : J. S. Lee : H. D. Kim Department of Pediatrics, Gangnam Severance Hospital, Severance Children’s Hospital, Yonsei University College of Medicine, PO Box 1217, 712 Eonjuro, 146-92 Dogok-dong, Gangnam-gu 135-720 Seoul, Korea e-mail: [email protected]

Keywords Mitochondria . Iron deficiency . Respiratory chain . Childhood

Introduction Mitochondrial disease is caused by abnormal intracellular adenosine triphosphate (ATP) production in mitochondrial respiratory chain complex (MRC) (Zeviani and Di Donato, 2004). A patient with MRC defect shows symptoms that are related to various organs, such as the brain, muscle, heart, liver, and kidney. In children with MRC defects, growth failure and developmental retardation are noted more frequently (Fadic and Johns 1996; Zeviani and Di Donato 2004; Debray et al. 2008). Iron is widely known to be one of the most important nutriments required for normal brain development and several essential metabolic functions, thus affecting functions of multiple organs (Lozoff et al. 1996; BorgnaPignatti and Marsella 2008). There have been several reports of the function of iron related to the brain (Logan et al. 2001; Boon 2002; Yager and Hartfield 2002; Maguire et al. 2007; Cortese et al. 2008). Iron deficiency (ID) is known to induce neurological symptoms such as developmental delay, pediatric stroke, breath-holding spells, and cranial nerve palsy (Yager and Hartfield 2002). It starts from a shortage of serum ferritin, the storage iron, then followed by a decrease in serum iron and transferrin saturation. Finally, it results in hemoglobin deficiency. Iron deficiency anemia (IDA) is diagnosed when this final step of hemoglobin deficiency is detected (Lanzkowsky 2005; Zimmermann 2008). Up to now, most investigations and studies have been conducted mainly on IDA but not on ID itself (Clark 2008). Various clinical symptoms can appear with ID only before

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Metab Brain Dis (2010) 25:185–189

Materials and methods

15 ng/mL in those older than 5 years of age (Zimmermann 2008). In cases with infection or inflammation, deficiency can diagnosed if serum ferritin is lower than 30 ng/mL since ferritin, being an acute phase protein, tends to increase in those situations (Lozoff et al. 1996; Zimmermann 2008). We set the basis of low hemoglobin level as under 11 g/dL in children between 1 year and 6 years of age and under 11.5 g/dL in those between 6 year and 12 years of age. Low transferrin saturation was defined as lower than 15% (Zimmermann 2008).

Patients and controls

Statistical analysis

We retrospectively analyzed the medical records of 69 patients diagnosed with MRC defects on muscle biopsy and those of 44 aged-matched controls. Subjects were between the ages of 1 year and 12 years and underwent iron metabolism examination at Gangnam Severance Hospital between January 2007 and November 2008.

We analyzed the differences in laboratory workups, neuroimaging studies, and clinical symptoms between patients with mitochondrial disease and the control group. Data are presented as mean±standard deviation (SD), and statistical analyses were performed by t-test protocol. Results were considered statistically significant with a p value of
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