2 articles
Congenital disorders of glycosylation (CDG) represent a group of rare diseases with multisystem involvement and exponential expansion, characterized by defects in the glycosylation process, which is essential for the proper functioning of proteins and lipids. These often manifest under the guise of other pathologies. The objective of the study was to diagnose CDG using Isoelectric Focusing of Transferrin (IEFT) in the Republic of Moldova and to identify diseases that mimic CDG.
Following medical-genetic consultations at the Institute of Mother and Child, 320 patients suspected for CDG were selected. History, clinical and paraclinical data were collected, and the proposed research questionnaire was completed. After signing the informed consent, the biological samples (serum, plasma, urine, DNA, DBS) were collected from all patients. Screening serum using the IEFT method was performed for 150 patients due to limited availability of reagents. For cases with negative CDG results, selective molecular-genetic tests such as MLPA, CGH-array, WES/WGS were performed.
Clinical and paraclinical examination of patients suspected CDG revealed multisystem involvement in 99.1% of cases, predominantly affecting the central nervous system in 92.2%. System and organ evaluation showed that, in addition to neurological damage there were skeletal (22.5%), renal (10.9%), ophthalmological (38.8%), muscular (22.5%), hepatic (20.9%), cardiac (40.6%), auditory (5.9%), pulmonary (3.8%), and gastrointestinal (29.4%) involvement. Analysis of 150 serum samples by IEFT method identified 3 positive cases for CDG. Molecular genetic testing revealed additional two CDG cases with negative IEFT and over 50 rare pathologies that manifest under the guise of CDG.
Clinical heterogeneity and disruptions in various biological pathways contribute to the complexity of CDG diagnosis. The clinical overlap of genetic diseases represents a considerable challenge for clinicians, as similar symptoms between different genetic conditions can lead to confusion and delay in identifying the disease.
Inborn errors of metabolism (IEM) make up a large group of disorders caused by an inherited defect of proteins that have enzymatic, carrier, receptor or structural roles. The cumulative prevalence of IEM in different populations is around 1:500 – 800 newborns, despite the fact that some of these disorders are extremely rare when taken individually. Early recognition and intervention are essential to avoiding disastrous consequences associated with IEM. The phenotype of IEM patients is very heterogeneous and only in combination with specialized metabolic test it can lead to a correct diagnosis. The aim of the study was defined as evaluation of importance of plasma amino acid profile in the diagnosis of IEM.
Plasma amino acids quantification have been performed by high performance liquid chromatography on Shimadzu LC-20 with post column derivatization with OPA in 15 patients aged from 0 to 13 years old, selected through medical genetic counseling, based on inclusion and exclusion criteria. Inform consent has been signed by parents after receiving all necessary information regarding the study. Additionally, liquid chromatography-tandem mass spectrometry (LC-MS/MS) on dried blood spots and Nuclear Magnetic Resonance Spectroscopy (H1-NMR) on urine has been done as complementary tests.
The first line investigations showed acid-base imbalance (33,3%), hypoglycemia (46,6%), high lactate level (46,6%) and high ammonia level (20%). Plasma amino acid concentrations were abnormal in 4 patients (27%). Increased glycine (544 μmol/L, reference values 70,72 – 256,36 μmol/L), along with elevated glycine in cerebrospinal fluid (CSF) / plasma ratio (0,147, normal < 0.02) was detected in a patient with seizures, coma, and respiratory arrest indicating non-ketotic hyperglycinemia. High level of phenylalanine (Phe 1568µmol/L, reference values 26.52 – 221 µmol/L) has been identified in a patient suspected for Phenylketonuria after neonatal screening results (Phe > 3mg/dL). Also the ratio Phe / Tyr around 17 was specifically appreciated as for classical form of PKU. High alanine concentration (> 450 µmol/L) has been observed in two patients presenting severe metabolic acidosis and high lactate level, suggesting for a metabolic error with mitochondrial involvement. The results from extended newborn screening and NMR spectroscopy narrowed the spectrum of suspected diseases, facilitating the diagnosis. Molecular genetic tests are required for the confirmation of disease in all cases.
Quantitative amino acids analysis is an important tool for the diagnosis of “intoxication type” of IEMs and nutritional monitoring of individuals with already established diagnosis.