Fifteen years experience: Egyptian metabolic lab

Biochemical diagnosis of Sanfilippo disorder types A and B

BACKGROUND

One of the 11 recognized mucopolysaccharidosis (MPS) diseases is Sanfilippo. It is autosomal recessive in its mode of transmission. There are four subtypes of Sanfilippo (A, B, C, and D). The most worldwide prevalent subtypes of mucopolysaccharidosis type III (MPS III) are A and B followed by C and D subtypes. To estimate the frequency of MPS IIIA among MPS III patients, we diagnose and compare their clinical features with those of MPS IIIB and also compare the prevalence of MPS IIIB versus MPS IIIA among diagnosed cases at the Biochemical Genetic Department at NRC. For every case that was referred, the quantitative determination of urine Glycosaminoglycans (GAGs) was assessed. Two-dimensional electrophoresis (2DE) of GAGs extracted from urine was performed on all cases with high urinary GAG levels. Both N-sulphoglucosamine sulphohydrolase (MPS IIIA) and N-alpha-acetylglucosaminidase (MPS IIIB) enzyme activity were determined fluorometrically.

RESULTS

From November 2019 to May 2022, 535 cases were referred to the National Research Centre's Biochemical Genetics Department. 233 (43%) MPS cases were diagnosed with high urinary GAG levels for their ages. 73 (31.3%) MPS III cases were diagnosed by 2DE out of the 233 MPS cases. Plasma N-alpha-acetylglucosaminidase enzyme assay was insufficient in 36 (49.3%) patients (Sanfilippo type B), while N-sulphoglucosamine sulphohydrolase enzyme activity was deficient in 15 (20.6%) patients. The other 22 (30.1%) patients are either Sanfilippo type C or D.

CONCLUSION

N-sulphoglucosamine sulphohydrolase enzyme activity was measured for the first time in Egypt. Thirty-one percent of all diagnosed MPS cases during the last 3 years were MPS type III, making Sanfilippo the most common MPS type among the referred cases to our Biochemical Genetics Department. MPS IIIA accounts for 20.6% of MPSIII cases in this study. Still, MPS type IIIB is the commonest type among diagnosed patients.

Inherited metabolic disorders in a cohort of Egyptian children

Background

Inborn errors of metabolism (IEMs) represent a special challenge in pediatric practice. Despite the unquestionable clinical significance of newborn screening, it just offers a snapshot of an extremely minor subgroup of metabolic disorders. So, it is crucial to use multiple techniques for accurate diagnosis of a wider spectrum of IEMs early in infancy to prevent overwhelming irreversible neurological complications in a cohort of high-risk Egyptian pediatrics. This study included four thousand and eighty suspected IEMs patients. They were referred to the Chromatography Unit, Clinical Biochemistry and Molecular Diagnostics Laboratories, National Liver Institute (NLI) for laboratory assessment in the period from March 2016 to November 2020. Separation of amino acids and acylcarnitines using tandem mass spectrometry (LC/MS) and organic acids using gas chromatography mass spectrometry (GC/MS) was done.

Results

Three hundred and twenty (320/4080, 7.8%) patients were diagnosed with IEMs. The following disorders were identified: organic acidopathies—200 (62.5%) including methylmalonic acidemia (MMA) (48/320, 15%), glutaric academia (GA) (40/320, 12, 5%), propionic acidemia (PA), (32/320, 10%), isovaleric acidemia (IVA) (40/320, 12.5%), methylcrotonyl glyceinuria (16/320, 5%), and orotic acidemia (24/320, 7.5%); amino acidopathies—80 (25%) including maple syrup urine disease (MSUD) (32/320, 10%), phenylketonuria (24/320, 7.5%), homocystinuria (16/320, 5%), and nonketotic hyperglycinemia (8/320, 2.5%) in addition to fatty acid disorders (FAO): 24 (7.5%) and lactic academia (LA), 16 (5%).

Conclusion

Early detection of IEMs by rapid non-invasive techniques. LC/MS and GC/MS. is a crucial process for early diagnosis of different types of IEMs to install therapeutic clue in a group of high-risk Egyptian pediatrics for proper treatment and better outcome

N- and O-glycan analysis for the detection of glycosylation disorders

Background

Congenital disorders of glycosylation (CDGs) are defined as a group of several rare autosomal recessive inborn errors of metabolism that affect the glycosylation of many proteins and/or lipids. Variable clinical presentation is very characteristic for all types of CDGs; symptoms include severe neurological manifestations that usually start in the neonatal period and cause aggressive irreversible neurological damage. These disorders are usually misdiagnosed as other non-inheritable disorders or remain undiagnosed for a long time, leading to severe neurological complications. The diagnosis of CDGs is quite tedious due to their diverse clinical presentation. In Egypt, there is still no available screening programme to detect CDGs in patients at a young age. Therefore, the need for a reliable rapid test that uses a small sample size has emerged.

This study included 50 suspected subjects and 50 healthy controls with matching age and sex. Western blotting and liquid chromatography-tandem mass spectrometry were used for the analysis of N- and O-glycans, respectively.

Results

The study detected 9 patients with hypoglycosylation (18%). Eight of the nine patients showed abnormal separation of N-glycoproteins using Western blotting indicative of reduced glycosylation (16% of the study subjects and 89% of the subjects with hypoglycosylation). Only one of the nine patients showed a decreased level of sialyl-T-antigen with a normal T-antigen level leading to an increased T/ST ratio (2% of study subjects and 11% of the subjects with hypoglycosylation).

Conclusion

Although N- and O-glycan analysis did not determine the underlying type of CDG, it successfully detected hypoglycosylation in 9 clinically suspected patients (18% of the studied subjects). All detected CDG cases were confirmed by molecular analysis results of mutations causing 4 different types of congenital disorders of glycosylation.

Mucopolysaccharidoses diagnosis in the era of enzyme replacement therapy in Egypt

BACKGROUND

Undegraded glycosaminoglycans (GAGs) induced by deficiency of enzymes are the primary cause of mucopolyscchardoses. Mucopolysacchardoses (MPS) are a group of rare lysosomal storage diseases (LSD). The quantification of a specific enzymatic activity is needed for accurate diagnosis. The objectives of this work were: first, to continue the study of mucopolysacchardoses disease in Egypt after the start of using the enzyme replacement therapy (ERT). Second, to define the commonest types among our population after 18 years experience with the disease. Third, to compare the different MPS types' distribution, diagnosed after the start of the ERT, to identify the impact of using ERT on the number and type of diagnosed patients.

METHOD

Urinary GAGs were measured for all referred cases followed by two-dimensional electrophoretic separation for cases with high levels of GAGs; the specific enzyme activity was assayed for each type depending on the abnormal electrophoretic pattern obtained. Clinically suspected cases of Morquio syndrome were directly subjected to measuring the specific enzyme.

RESULTS

Out of 1448 suspected cases, 622 (42.9%) MPS patients were diagnosed revealing the following distribution: MPS I (172, 27.7%), MPS II (57, 9.1%), MPS III [(177, 28.5%: 134 type B and 43 types A, C or D)], MPS IVA (124, 19.9%), MPS VI (90, 14.5%) and MPS VII (2, 0.3%). MPS III was the most commonly diagnosed type followed by MPS I and MPS IVA. MPS IVA represented the most common type receiving treatment, followed by MPS I, MPS II and MPS VI.

CONCLUSION

The presence of treatment encouraged the affected families and physicians to seek diagnosis. MPS III was the commonest type among our studied group after 7 years of diagnosis, while MPS IVA was the commonest type receiving treatment.

Detection of some metabolic disorders in suspected neonates admitted at Assiut University Children Hospital

Background

Inborn errors of metabolism are genetically inherited diseases which can lead to accumulation of toxic metabolites in the body. Inborn errors of metabolism have a high morbidity and mortality in neonates. Many inborn errors of metabolism are amenable to treatment with early diagnoses. Till now, more than 500 metabolic disorders have been detected. Although individual metabolic disorders are rare, the incidence of overall metabolic disorders is high.

Results

It was found that 70/200 cases (35 %) had confirmed inborn errors of metabolism, and another 8 cases (4%) suspected to have inborn errors of metabolism; 15/200 (7.5%) cases had mild elevation of phenylalanine level, while 107/200 (53.5%) had another diagnosis rather than metabolic disorders. Urea cycle defect was diagnosed in 20/70 (28.5%), maple syrup urine disease in 18/70 (25.7%), organic acidemia in 15/70 (21.4%), and non-ketotic hyperglycinemia in 1/70 (1.4 %) case. Also, 15/70 (21.4 %) cases had fatty acid oxidation defect. Lastly, one female case (1.4 %) was diagnosed to have disorder of pyrimidine deficiency.

Conclusion

Diagnosis of inborn errors of metabolism was confirmed in 35% of neonates, and 4% was suspected to have metabolic disorders. These results showed that inherited metabolic disorders are not rare. The development of a nationwide screening program for metabolic disorders is mandatory for early detection of these potentially treatable disorders.

Research, diagnosis and education in inborn errors of metabolism in Colombia: 20 years' experience from a reference center

The use of specialized centers has been the main alternative for an appropriate diagnosis, management and follow up of patients affected by inborn errors of metabolism (IEM). These centers facilitate the training of different professionals, as well as the research at basic, translational and clinical levels. Nevertheless, few reports have described the experience of these centers and their local and/or global impact in the study of IEM. In this paper, we describe the experience of a Colombian reference center for the research, diagnosis, training and education on IEM. During the last 20 years, important advances have been achieved in the clinical knowledge of these disorders, as well as in the local availability of several diagnosis tests. Organic acidurias have been the most frequently detected diseases, followed by aminoacidopathies and peroxisomal disorders. Research efforts have been focused in the production of recombinant proteins in microorganisms towards the development of new enzyme replacement therapies, the design of gene therapy vectors and the use of bioinformatics tools for the understanding of IEM. In addition, this center has participated in the education and training of a large number professionals at different levels, which has contributed to increase the knowledge and divulgation of these disorders along the country. Noteworthy, in close collaboration with patient advocacy groups, we have participated in the discussion and construction of initiatives for the inclusion of diagnosis tests and treatments in the health system.

Lysosomal Storage Disorders in Egyptian Children

OBJECTIVE

To describe the spectrum, relative prevalence and molecular background of lysosomal storage disorders in Egypt.

METHODS

The authors evaluated the selective screening program for the diagnosis of lysosomal storage disorders in Egyptian children presenting to the inherited metabolic disease unit at Cairo University Children's Hospital, the largest tertiary care pediatric hospital in Egypt, over a six-year period (April 2008 through April 2014). During this period, 1,065 suspected children were assessed clinically, biochemically and some genetically.

RESULTS

Two hundred and eleven children (aged 44 ± 32 mo; 56 % boys, 82 % with consanguineous parents) were confirmed with 21 different lysosomal disorders. The diagnostic gap ranged between 2 mo and 14 y (average 25 mo). Mucopolysaccharidoses were the most common group of diseases diagnosed (44.5 %), while Maroteaux-Lamy, Gaucher and nephropathic cystinosis were the most commonly detected syndromes (17.1, 14.7 and 13.7 %, respectively). Eighty mutant alleles and 17 pathogenic mutations were detected in 48 genetically assessed confirmed patients (30 Gaucher, 16 cystinosis and two Niemann-Pick type C patients).

CONCLUSIONS

This report is the first to describe relative frequency and spectrum of clinical and molecular data in a large cohort of Egyptian lysosomal patients. The crude estimate denotes that over 80 % of Egyptian lysosomal patients do not have access to optimal diagnosis. Upgrading diagnostic and genetic services for lysosomal storage disorders in Egypt is absolutely necessary.