Experience of King Faisal Specialist Hospital and Research Center with Saudi organic acid disorders

Screening for organic acidurias and aminoacidopathies in high-risk Brazilian patients: Eleven-year experience of a reference center

Organic acidurias and aminoacidopathies are groups of frequent inborn errors of metabolism (IEMs), which are caused by mutations in specific genes that lead to loss of protein/enzyme or transport function with important deleterious effects to cell metabolism. Since a considerable number of such disorders are potentially treatable when diagnosed at an early stage of life, diagnosis is crucial for the patients. In the present report, we describe symptomatic individuals referred to our service that were diagnosed with these disorders from 2006 to 2016. We used blood and urine samples from 21,800 patients suspected of aminoacidopathies or organic acidemias that were processed by the analytical techniques reverse phase high-performance liquid chromatography for amino acid quantification and gas chromatography coupled to mass spectrometry for organic acid detection. Analysis of dried blood spots by liquid chromatography-tandem mass spectrometry was used in some cases. We detected 258 cases of organic acidurias, and 117 patients with aminoacidopathies were diagnosed. Once diagnosis was performed, patients were promptly submitted to the available treatments with clear reduction of mortality and morbidity. The obtained data may help pediatricians and metabolic geneticists to become aware of these diseases and possibly expand newborn screening programs in the future.

Spectrum of mutations underlying Propionic acidemia and further insight into a genotype-phenotype correlation for the common mutation in Saudi Arabia

Propionic acidemia (PA) is an autosomal recessive metabolic disorder. PA is characterized by deficiency of the mitochondrial enzyme propionyl CoA carboxylase (PCC) that results in the accumulation of propionic acid. Alpha and beta subunits of the PCC enzyme are encoded by the PCCA and PCCB genes, respectively. Pathogenic variants in PCCA or PCCB disrupt the function of the PCC enzyme preventing the proper breakdown of certain amino acids and metabolites. To determine the frequency of pathogenic variants in PA in our population, 84 Saudi Arabian patients affected with PA were sequenced for both the PCCA and PCCB genes. We found that variants in PCCA accounted for 81% of our cohort (68 patients), while variants in PCCB only accounted for 19% (16 patients). In total, sixteen different sequence variants were detected in the study, where 7 were found in PCCA and 9 in PCCB. The pathogenic variant (c.425G > A; p.Gly142Asp) in PCCA is the most common cause of PA in our cohort and was found in 59 families (70.2%), followed by the frameshift variant (c.990dupT; p.E331Xfs*1) in PCCB that was found in 7 families (8.3%). The p.Gly142Asp missense variant is likely to be a founder pathogenic variant in patients of Saudi Arabian tribal origin and is associated with a severe phenotype. All variants were inherited in a homozygous state except for one family who was compound heterozygous. A total of 11 novel pathogenic variants were detected in this study thereby increasing the known spectrum of pathogenic variants in the PCCA and PCCB genes.

Autism in patients with propionic acidemia

Certain inborn errors of metabolism have been suggested to increase the risk of autistic behavior. In an animal model, propionic acid ingestion triggered abnormal behavior resembling autism. So far only a few cases were reported with propionic acidemia and autistic features. From a series of twelve consecutively diagnosed cases with propionic acidemia, we report on eight patients with autistic features. The patients were followed 2-4 times a year and underwent regular clinical, dietary and laboratory investigations. Psychological evaluation was performed every second to fourth year. All patients were compliant with the standard diet and carnitine supplementation. None of the patients had frequent metabolic decompensations. From the metabolic factors known to impact neuropsychological outcome we detected chronically decreased valine levels and altered valine to leucine ratios in five out of the eight patients. Recurrent lactic acid elevations were present in six out of the eight patients. Five of the eight patients were diagnosed with Autism Spectrum Disorder, four of them had pathogenic variants in PCCB. Disorder according to DSM-IV and/or DSM-5 criteria. One of the patients diagnosed with propionic acidemia by newborn screening had the most significant behavioral features and another was diagnosed with Autism Spectrum Disorder prior to propionic acidemia. We hypothesize that chronic suboptimal intracellular metabolic balance may be responsible for the increased risk for autistic features in propionic acidemia. We propose that patients diagnosed with propionic acidemia should be screened for Autism Spectrum Disorder.

Incidence and Geographic Distribution of Succinic Semialdehyde Dehydrogenase (SSADH) Deficiency

The incidence of succinic semialdehyde dehydrogenase (SSADH) deficiency, an autosomal recessive inherited disorder of GABA degradation, is unknown. Upon a recent diagnosis of a new family of affected fraternal twins from the Punjabi ethnic group of India, case ascertainment from the literature and our database was done to determine the number of confirmed cases along with their geographic distribution. The probands presented with global developmental delay, infantile onset epilepsy, and a persistent neurodevelopmental disorder upon diagnosis at 10 years of age with intellectual disability, expressive aphasia, and behavioral problems most prominent for hyperactivity. Gamma-hydroxybutyric aciduria and homozygous ALDH5A1 c.608C>T; p.Pro203Leu mutations were confirmed. Identification of all available individual cases with clinical details available including geographic or ethnic origin revealed 182 patients from 40 countries, with the largest number of patients reported from the USA (24%), Turkey (10%), China (7%), Saudi Arabia (6%), and Germany (5%). This study provides an accounting of all published cases of confirmed SSADH deficiency and provides data useful in planning further studies of this rare inborn error of metabolism.

Genetics and psychotic disorders: A fresh look at consanguinity

Consanguineous unions refer to marriages between related individuals who share a common ancestor. These unions are still commonplace in certain regions of the world such as the southern coast of the Mediterranean, throughout the Middle East and South-East Asia. According to available data, couples of second cousins or closer and their offspring currently represent 10.4% of the world's population, thus resulting in increased frequencies of autosomal recessive disorders. Furthermore, consanguinity may be implicated in the increased frequency of multifactorial pathologies such as mental disorders. The few existing epidemiological studies in consanguineous and/or geographically isolated populations confirm that there is a significant association between consanguinity and mental disorders and a higher risk of schizophrenia or bipolar disorders among offspring from consanguineous couples. There exists a strong and complex genetic component in the predisposition to psychotic disorders that has been confirmed in numerous studies. However, the genetic basis of these disorders remains poorly understood. GWAS studies (Genome Wide Association Studies) over the past 10 years have identified a few weak associations, thus refuting the "common diseases-common variants" hypothesis. A model implicating numerous rare variants has been supported by the recent discovery of CNVs (Copy Number Variants) and their statistically significant association with psychiatric disorders such as schizophrenia, bipolar disorders and autism. The study of consanguineous families may contribute to identifying rare variants in homogenous populations who have conserved certain alleles. Major developments in molecular biology techniques would facilitate these studies as well as contributing to identifying major genes. These results emphasize the need for genetic counseling in high-risk communities and the importance of implementing preventive actions and raising awareness concerning the risk of consanguineous unions.

Diagnosis and clinical features of organic acidemias: A hospital-based study in a single center in Damascus, Syria

Background: Organic acidemias (OA) are a group of heterogeneous metabolic inherited disorders characterized by the accumulation of organic acids in body fluids and tissues. These are rare disorders and infrequently reported worldwide. In Syria, there is a lack of information regarding these disorders. Objective: Our hospital-based study aimed to describe the pattern of clinical and demographic presenting features of organic acidemias among Syrian children and to shed light on the diagnostic experience of organic acidemias in the Children's Hospital of Damascus through a five year period. Material and methods: We conducted a retrospective cohort study by reviewing the medical records of OA patients in the Children's Hospital of Damascus between 2008 and 2012. All cases were investigated by metabolic work up, including the acylcarnitine profile performed by tandem mass spectrometry (MS/MS) and quantitative urine organic acid analysis performed by gas chromatography mass spectrometry (GC-MS). Results: A total of 70 OA confirmed cases were included in the study. There were 46 males and 31 females. Twenty-seven cases were diagnosed after the first year of life. Methylmalonic acidemia was the most frequent disorder (57.1%). There were relatively high rates of family history of unexplained death and OA confirmed cases (50%), consanguinity (74.2%) and mortality (21.4%). The most frequent symptoms were apnea or respiratory distress (65.7%) and vomiting (40%). Conclusion: The lack of specific confirmatory diagnostic tests being performed and the high mortality and consanguinity rates among OA patients suggests high incidence of OA in Syria. Further studies are needed to determine the actual incidence of OA and the cost-effectiveness of applying a governmental mandatory newborn screening program.

A novel PCCB mutation in a Thai patient with propionic acidemia identified by exome sequencing

Propionic acidemia (PA) is an inborn error of metabolism, caused by mutations in either the PCCA or PCCB gene, leading to mitochondrial accumulation of propionyl-CoA and its by-products. Here we report a 6-year-old Thai boy with PA who was born to consanguineous parents. Exome sequencing identified a novel homozygous frameshift insertion (c.379_380insA; p.T127NfsX160) in the PCCB gene, expanding its mutational spectrum.

Propionic acidemia in the Arab World

The autosomal recessive disease propionic acidemia (PA) is an inborn error of metabolism with highly variable clinical manifestations, caused by a deficiency of propionyl-CoA carboxylase (PCC) enzyme, due to mutations in either PCCA or PCCB genes, which encode the alpha and beta subunits of the PCC enzyme, respectively. The classical clinical presentation consists of poor feeding, vomiting, metabolic acidosis, hyperammonemia, lethargy, neurological problems, and developmental delay. PA seems to be a prevalent disease in the Arab World. Arab patients with PA seem to have the same classical clinical picture for PA with distinctive associated complications and other diseases. Most of the mutations found in Arab patients seem to be specific to the Arab population, and not observed in other ethnic groups. In this review, I will discuss in details the clinical and molecular profile of Arab patients with PA.

Autism spectrum disorders and inborn errors of metabolism: an update

BACKGROUND

Autism spectrum disorder is characterized by social communicative deficits with restricted interests occurring in about 1% of the population. Although its exact cause is not known, several factors have been implicated in its etiology, including inborn errors of metabolism. Although relatively uncommon, these disorders frequently occur in countries with high rates of consanguinity and are often associated with behavioral problems, such as hyperactivity and aggression. The aim of this review is to examine the association of autism with these conditions.

METHOD

A computer-assisted search was performed to identify the most common inborn errors of metabolism associated with autism.

RESULTS

The following disorders were identified: phenylketonuria, glucose-6-phosphatase deficiency, propionic acidemia, adenosine deaminase deficiency, Smith-Lemli-Opitz syndrome and mitochondrial disorders, and the recently described branched chain ketoacid dehydrogenase kinase deficiency.

CONCLUSION

The risk of autistic features is increased in children with inborn errors of metabolism, especially in the presence of cognitive and behavioral deficits. We propose that affected children should be screened for autism.

Selective newborn screening of inborn errors of amino acids, organic acids and fatty acids metabolism in the Kingdom of Bahrain

Mandatory newborn screening for metabolic disorders has not been implemented in most Middle Eastern countries. Early detection and treatment of inborn errors of metabolism can reduce mortality and minimize morbidity. Preliminary studies conducted in some parts of Middle East suggest that the incidences of inborn errors of metabolism are reported to be higher in the region than anywhere else in the world due to the consanguinity. In this study the incidence of inborn errors of amino acids, organic acids and fatty acids oxidation disorders was investigated from the results of blood spot analysis of 1986 symptomatic children from 1st January 2008 to 31st of December 2011. Out of 1986 newborns screened 25 infants were diagnosed and confirmed with amino acids (n=11), organic acids (n=9) and fatty acids oxidation (n=5) disorders. Overall incidences based on number of live birth between 2008 and 2011 inclusive were 1:6000, 1:8000 and 1:14,000 for amino acids, organic acids and fatty acids oxidation disorders; respectively. Out of 25 infants diagnosed, 21 were the children of first cousin marriages. Results from this study suggest high incidence of inborn errors of amino acids, organic acids and fatty acids oxidation metabolism in Bahrain and significant contribution of consanguinity in inherited metabolic disorders. Mandatory screening for inborn errors of metabolism in Bahrain is highly recommended.

Propionic acidemia associated with visual hallucinations

Propionic acidemia, an autosomal recessive disorder, is a common form of organic aciduria resulting from the deficiency of propionyl-CoA carboxylase. It is characterized by frequent and potentially lethal episodes of metabolic acidosis often accompanied by hyperammonemia. A wide range of brain abnormalities have been reported in propionic acidemia. We report recurrent visual hallucinations in 2 children with propionic acidemia. Four visual hallucination events were observed in the 2 patients. Three episodes were preceded by an intercurrent illness, and 2 were associated with mild metabolic decompensation. The 2 events in one patient were associated with a seizure disorder with abnormal electroencephalogram. Brain magnetic resonance imaging showed abnormal basal ganglia and faint temporo-occipital swelling bilaterally. This is probably the first report of visual hallucinations in propionic acidemia and should alert the treating clinicians to look for visual hallucinations in patients with organic acidurias, especially in an unusually anxious child.

Diagnosis of major organic acidurias in children: two years experience at a tertiary care centre

Organic acid disorders are inherited metabolic disorders in which organic acids accumulate in tissues and biological fluids of affected individuals. Classical organic acidurias include methylmalonic aciduria, propionic aciduria, isovaleric aciduria and maple syrup urine disease (MSUD). They are considered the most frequent metabolic disorders among severely ill children. Patients frequently present with acute symptoms early in life. 420 cases clinically suspected to have organic aciduria, with upper age limit of 12 years for a 2-year period (January 2007-December 2008) were enrolled into this study. Metabolic acidosis and neurological symptoms were the most common signs. Screening tests and thin layer chromatography were done for detection of organic acidurias. Identification and quantitation of organic acids in urine and quantification of amino acids in blood were done by high performance liquid chromatography. Out of 420 patients, 45 patients (10.7%) were found to have organic acidurias. 15 cases of methylmalonic aciduria, 16 cases of propionic aciduria, 13 cases of MSUD, and one case of isovaleric aciduria were diagnosed. Results demonstrate the importance of testing for organic acidurias. Since organic aciduria may cause irreversible brain damage if not treated, we recommend selective screening amongst severely ill children despite implied extra costs.

Incidence and patterns of inborn errors of metabolism in the Eastern Province of Saudi Arabia, 1983-2008

BACKGROUND AND OBJECTIVES

Individual inborn errors of metabolism (IEM) are rare disorders, but may not be that uncommon in our patient population. We report the incidence of IEM in a defined cohort of births at the Saudi Aramco medical facilities in the Eastern Province of Saudi Arabia over 25 years.

METHODS

The records of all patients diagnosed with IEM from 1 January 1983 to 31 December 2008 were reviewed and categorized according to accumulated or deficient metabolites into small-molecule disorders (aminoacidemia, organic acidopathies [OA], urea cycle defects, fatty acid oxidation, and carbohydrate metabolic disorders) and other disorders, including glycogen and lysosomal storage disorders (LSDs), and organelle disorders.

RESULTS

During the study period, 165,530 Saudi Arabian infants were born at Saudi Aramco and 248 were diagnosed with an IEM, corresponding to a cumulative incidence of 150 cases per 100,000 live births. Small-molecule disorders were diagnosed in 134/248 patients (54%). OA were the most common (48/248 patients; 19%), and methylmalonic aciduria was the most frequently observed OA (13/48 patients; 27%). LSDs were diagnosed in 74/248 patients (30%), and mucopolysaccharidosis was the most frequently observed LSD (28/74; 38%).

CONCLUSION

We believe that our data underestimate the true incidence of IEM in the region. Regional and national newborn screening programs will provide a better estimation of the incidence of IEM. We recommend a centralized newborn screening program that employs tandem mass spectrometry.

Evolution in health and medicine Sackler colloquium: Consanguinity, human evolution, and complex diseases

There is little information on inbreeding during the critical early years of human existence. However, given the small founding group sizes and restricted mate choices it seems inevitable that intrafamilial reproduction occurred and the resultant levels of inbreeding would have been substantial. Currently, couples related as second cousins or closer (F >or= 0.0156) and their progeny account for an estimated 10.4% of the global population. The highest rates of consanguineous marriage occur in north and sub-Saharan Africa, the Middle East, and west, central, and south Asia. In these regions even couples who regard themselves as unrelated may exhibit high levels of homozygosity, because marriage within clan, tribe, caste, or biraderi boundaries has been a long-established tradition. Mortality in first-cousin progeny is approximately 3.5% higher than in nonconsanguineous offspring, although demographic, social, and economic factors can significantly influence the outcome. Improving socioeconomic conditions and better access to health care will impact the effects of consanguinity, with a shift from infant and childhood mortality to extended morbidity. At the same time, a range of primarily social factors, including urbanization, improved female education, and smaller family sizes indicate that the global prevalence of consanguineous unions will decline. This shift in marriage patterns will initially result in decreased homozygosity, accompanied by a reduction in the expression of recessive single-gene disorders. Although the roles of common and rare gene variants in the etiology of complex disease remain contentious, it would be expected that declining consanguinity would also be reflected in reduced prevalence of complex diseases, especially in population isolates.

Newborn screening: experiences in the Middle East and North Africa

This review presents the current experiences with newborn screening in the Middle East and North Africa region. The population in the region is about 400 million, with high birth rate and an estimated 10 million newborns per year. The majority of the population is of the Islamic faith and mostly Arab. The population is characterized by a high consanguinity (25-70%) and a high percentage of first-cousin marriages. Haemoglobin disorders, inherited metabolic disorders, neurogenetic disorders and birth defects are relatively common among the population. There is a rather slow progress in developing and implementing preventive genetic programmes owing to legal, cultural, political and financial issues. Although research spending is rather soft in the region, there are numerous pilot studies that highlighted the high incidence of genetic defects and the need for newborn screening programmes. Currently, there are only four countries that are executing national newborn screening but they vary from one disease to 23 and coverage is not complete. The region needs to take big steps towards developing national strategies for prevention and should learn from experiences of regional and international screening programmes.

Detection of organic acidemias in Brazil

BACKGROUND

Organic acidurias or organic acidemias are inherited metabolic disorders in which organic acids (carboxylic acids) accumulate in tissues and physiologic fluids of affected individuals. They are considered the most frequent metabolic disorders among severely ill children. Patients frequently present acute symptoms in early life. Metabolic acidosis and neurologic symptoms are the most common signs.

METHODS

Urine specimens obtained from 1,926 children from January 1994 to July 2001 were used in analyses. Venous blood specimens were also collected from some patients. Samples were initially submitted to screening tests for detection of inborn errors of metabolism. Identification and semi-quantitation of organic acids in urine were performed by gas chromatography or gas chromatography coupled to mass spectrometry using capillary column (DB-5) and flame ionization detection.

RESULTS

Ninety three (4.8%) cases of organic acidemias were diagnosed among 1,926 patients investigated from January 1994 to July 2001. Prompt therapy was instituted after diagnosis in a considerable number of patients and resulted in rapid improvement in their symptomatology, distinct from our previous cases diagnosed abroad where patients representing index cases died before any measure could be taken.

CONCLUSIONS

Results demonstrate the importance of diagnosing organic acidurias in loco in developing countries despite implied extra costs.

18Fluoro-2-deoxyglucose (18FDG) PET scan of the brain in propionic acidemia: clinical and MRI correlations

The clinical data and the imaging findings of the positron emission tomography (PET) and the magnetic resonance imaging (MRI) studies in five patients, previously diagnosed to have propionic acidemia, were retrospectively reviewed. The patients were all normal at birth. The first clinical signs, typically hypotonia and failure to thrive, appeared during the first 2 years of life. With progression of the disease, the neurological findings consisted of variable degrees of dementia and extrapyramidal symptoms, notably dystonia, choreoathetosis and rigidity of variable degrees. Initial cerebral PET and MRI studies were normal. Follow-up MRI examinations showed progressive basal ganglia degeneration, with evidence of atrophy and signal abnormalities within the caudate nuclei and the putamina. The thalamic structures were normal. The PET studies demonstrated increased uptake in the basal ganglia and thalami, followed by decreased uptake in the basal ganglia at a later stage of the disease. The structural (MRI) and the functional (PET) studies of the brain were found to be complementary in the evaluation of propionic acidemia, and were in good correlation with the clinical findings.

Infectious complications of propionic acidemia in Saudia Arabia

A retrospective study of 38 patients with propionic acidemia indicates a high frequency of infections; affecting 80% of such patients. The Saudi Arabian population studied is a product of consanguineous marriages, and presents with a severe phenotype. Most microorganisms implicated are unusual, which suggests an underlying immune deficiency. These frequent infections occur despite aggressive treatment with appropriate diets, carnitine and during acute episodes of the disease with metronidazole, which suggests a global effect of the disease on T and B lymphocytes as well as on the bone marrow cells. Any patient with propionic acidemia should be closely followed up for an intercurrent infection in association with acute metabolic decompensation.

Comparative frequency and severity of hypoglycemia in selected organic acidemias, branched chain amino acidemia, and disorders of fructose metabolism

The Institution's experience with hypoglycemia in different types of organic acidemias, branched chain amino acidemia (MSUD), and disorders of fructose metabolism was reviewed retrospectively. The charts of 144 patients who were followed for 1-5 years were studied for the severity and frequency of hypoglycemia. The patients were mainly Saudi; however, 10-25% were from neighboring countries. Therefore, the observations pertain to the genetic groups in the Arabian peninsula. Organic acidemias which primarily manifest with neurologic signs, such as 4-hydroxybutyric aciduria, infantile onset 3-methylglutaconic aciduria, and glutaric aciduria type 1 never showed hypoglycemia. Patients with beta-ketothiolase deficiency, biotinidase deficiency, or intermittent or intermediate MSUD, also did not have hypoglycemia during metabolic crisis. Hypoglycemia was rare and mild among neonates with classic MSUD, ethylmalonic aciduria, and isovaleric acidemia. Less than 50% of the patients with MSUD older than 8 months, pyruvate carboxylase deficiency, methylmalonic acidemia, or propionic acidemia had hypoglycemia during metabolic crisis. On the other hand, patients with 3-hydroxy-3-methyl glutaryl-CoA lyase deficiency, holocarboxylase synthetase deficiency, medium or long-chain acyl-CoA dehydrogenase deficiency, neonatal onset 3-methylglutaconic aciduria, glutaric aciduria type 2, and disorders of fructose metabolism invariably had moderate-to-severe hypoglycemia associated with metabolic crisis. The purpose of this report is to provide the pediatrician, particularly in the Middle East, with a diagnostic guideline to the identification and management of different types of organic acidemias, based on co-existing hypoglycemia.

Movement disorders in childhood organic acidurias. Clinical, neuroimaging, and biochemical correlations

Over the last 5 years the Pediatric Neurology service at King Faisal Specialist Hospital and Research Centre (KFSH&RC) has seen 131 infants and children with movement disorders. Forty-nine (37%) had identifiable biochemical defects, 25 of which were organic acidemias. Nineteen of 29 patients with dystonia had organic acidemias, primarily glutaric aciduria type 1 (7 patients), bilateral striatal necrosis (4 patients), and 3-methyl glutaconic aciduria (3 patients). All patients with parkinsonian rigidity (n = 11) had organic acidemias; again, the greatest number accounted for by glutaric aciduria type 1 (7 patients), who had both parkinsonian rigidity combined with dystonia. Myoclonus occurred in only 1 of 25 and chorea in 7 of 25 patients with organic acidemias. At the least all patients had bilateral lesions of putamen and head of caudate, seen best in MRI brain scans as increased T2 signal intensities with normal volume, and later with volume loss.

Emergency presentations of patients with methylmalonic acidemia, propionic acidemia and branched chain amino acidemia (MSUD)

The charts of 16 patients with branched chain amino acidemia (MSUD) who had 48 emergency room (ER) visits, of 10 patients with propionic acidemia (PA) who had 57 ER visit, and of 13 patients with methylmalonic acidemia (MMA) who had 154 ER visits, were reviewed retrospectively for the most common clinical presentations, physical and laboratory findings. The most common clinical presentation was acute or chronic vomiting and the most common physical finding was dehydration. When hypoglycemia was found, the mental status of 55% of patients with MSUD and MMA and 20% of patients with PA, was alert. Mixed acid/base disturbance, i.e. alkalosis caused by vomiting mixed with metabolic acidosis caused by the disease, was present in 30% of MSUD, in 33% of PA, and 45% of MMA. There was no relationship between acidosis detected by the blood pH and mental status of the patients. A good correlation between base excess < -5 and serum bicarbonate < 21 mmol/l was found. Blood cultures were positive for bacteria and fungi in 15% of the visits with MSUD, in 23% with PA, and 3% with MMA. Patients with positive blood cultures did not necessarily have a temperature > 39 degrees C nor hypothermia. The results suggest that the mental status of the patients should not detract the ER physician from obtaining blood pH, gases and glucose and in all instances a blood culture should be secured, even if the patient has no fever.