Study of neurometabolic disorders in Egyptian children

Background: Metabolic brain diseases usually present with a complex neurological picture so they are often overlooked. This prospective study was undertaken to focus on the clinical aspects, biochemical abnormalities and neuroimaging of the brain in children suffering from neurometabolic disorders

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Patients and methods: This study was carried out on 130 patients suspected clinically of having metabolic brain diseases and presented to the neuropediatric clinic, neonatal intensive care unit in Benha faculty of medicine and the neurometabolic specialized clinic in Abu El-Reesh hospital. The diagnosis of neurometabolic disorders was confirmed in 29 children [22%]. They were 19 males and 10 females, their age ranged from 5 days to 10 yrs with mean age 3.61 +/- 2.2 years. They presented with clinical manifestations suggestive of metabolic brain diseases. They were subjected to thorough history, clinical examination, investigations in the form of serum ammonia, serum lactate ,blood glucose, blood gases assessment, ketone bodies in urine, CPK [creatine phosphokinase],urine organic acids, plasma aminogram, enzymatic assay, EMG [Electromyography],EEG[electroencephalography], muscle biopsy, CT and MRI of the brain

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Results: Patients were classified according to their clinical presentations, biochemical and radiological findings into 5 groups, Group I, Organic acidemia 10 cases [34.5%], including, Methyl malonic acidemia [4 cases], Biotinidase deficiency [3 cases], Glutaric Aciduria type 1 [2 cases] and Maple syrup urine disease [one case]. Group II, Mitochondrial disorders 9 cases [31%] including, Leigh syndrome [4 cases], Pyruvate dehydrogenase deficiency [2 cases], mitochondrial encephalomyopathy [2 cases] and MELAS syndrome[mitochondrial encephalopathy, lactic acidosis and stroke] [one case]. Group III, Urea cycle abnormalities 5 cases [17.2 %]. Group IV Aminoacidopathy 3 cases [10.4 %]in the form of Phenylketonuria. Group V Fatty acid oxidation defect 2 cases [6.9%]. The main neurological manifestations were global developmental delay [93.1%], seizures [89.7%], hypertonia [65.5%] and microcephaly [55.2%]. Biochemical abnormalities were: Group I: had acidosis in 9 cases[90%] [ketoacidosis in [4 cases],lactic acidosis in[3 cases],acidosis without ketosis in [2 cases]], ketosis only in one case [10%] and hyperammonemia in 7 cases [70%] of cases. GroupII: had mainly lactic acidosis 5 cases [55.6%] and mild hyperammonemia [11.1%]. GroupIII: had isolated hyperammonemia [100%]. Group IV: had hyperphenylalaninemia in [100%] of cases with phenylketonuria. Group V: had lactic acidosis,mild hyperammonemia, hypoglycemia and absent ketosis in [100%]of cases. Neuroimaging showed abnormal findings in the form of basal ganglia abnormalities [41.4%], brain atrophy [27.5%], diffuse demeylination and focal demeylination [6.9%]each and normal findings in [17.3%]

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Conclusion: Presence of unexplained neurological symptoms whose severity is out of proportion to the inciting illness should arouse suspicion of a metabolic disease. Screening tests like blood gas analysis, blood levels of lactate, glucose and ammonia, urine examination for ketones and neuroimaging provide valuable clues to the presence of an underlying metabolic disease