Personalised medicine has become a central paradigm in modern healthcare, aiming to tailor prevention, diagnosis, and therapy to each patient's unique molecular and clinical profile. This paper provides a comprehensive overview of the lectures presented at the 36th annual Symposium of the Croatian society of medical biochemistry and laboratory medicine. It highlights key topics including the role of disease-causing variants in hereditary disorders, the development of cystic fibrosis transmembrane conductance regulator (CFTR) modulators, the evolution of newborn screening programs and spinal muscular atrophy diagnostics, emphasizing early detection and timely initiation of therapy, advances in cancer genetics, pharmacogenetics, and the translation of other laboratory-based innovations into clinical practice. Altogether, these advances reaffirm the central role of laboratory diagnostics as the cornerstone of personalised medicine, bridging genetic discovery with clinical translation and transforming modern healthcare into a predictive, preventive, and truly patient-centred discipline.

Fenilketonurija je autosomno recesivno nasljedna metabolička bolest uzrokovana bialelnim patogenim varijantama gena PAH koji kodira enzim fenilalanin hidroksilazu (PAH). Uslijed smanjene aktivnosti enzima PAH dolazi do poremećaja metabolizma aminokiseline fenilalanina te njegovog nakupljanja u tkivima i tjelesnim tekućinama. Liječenje zahtijeva cjeloživotnu strogu niskoproteinsku dijetu, uz obaveznu suplementaciju specijalnim medicinskim pripravcima kojima se osigurava dostatan unos ostalih esencijalnih aminokiselina i drugih esencijalnih nutrijenata. Pravovremena dijagnoza putem novorođenačkog probira i rani početak terapije ključni su za prevenciju razvoja intelektualnih teškoća i drugih teških neuroloških posljedica. Međutim, čak i uz cjeloživotno praćenje i dobru metaboličku kontrolu, bolesnici mogu imati poteškoće s pažnjom i kognitivnim funkcijama. Liječenje pacijenata u Republici Hrvatskoj provodi se sukladno važećim europskim smjernicama. Cilj ovog rada je predstaviti koncept edukativnog alata namijenjenog osobama s fenilketonurijom i njihovim obiteljima u Hrvatskoj. Alat je osmišljen kako bi se omogućilo jednostavnije i preciznije praćenje unosa fenilalanina i povećalo edukaciju korisnika te tako poboljšalo metaboličku kontrolu i kvalitetu života oboljelih.

Hypophosphatasia (HPP) is a rare, inherited metabolic disorder due to a deficiency of tissue-nonspecific alkaline phosphatase, characterized by defective bone and teeth mineralization with consequent problems, including respiratory failure in severe types of HPP. Severe patients exhibit other disease-related manifestations, including neurological manifestations, which make HPP complex and difficult to manage. Enzyme replacement therapy with asfotase alfa is a disease-specific treatment for skeletal manifestations in pediatric patients. We present a patient with perinatal HPP who had a severe clinical course with respiratory insufficiency during infancy requiring a higher dose of asfotase alfa than recommended (12 mg/kg/week). After improvement of respiratory function and outgrowing the higher dose, the patient was maintained on the standard dose (6 mg/kg/week) from the age of 3 years. At 6 years of age, unexplained clinical and radiographic deterioration occurred while laboratory parameters remained normal. Following a traumatic humerus fracture that occurred after several months, asfotase alfa was increased to 10 mg/kg/week. Remarkable clinical improvement was observed and the patient regained the ability to walk unassisted 3 months after the dose correction. The rickets severity score changed from 10 to 3.5 within 14 months. No side effects from the higher drug dose have been noticed. The remaining challenge in this patient was a neurodevelopmental disorder. In conclusion, the standard dose of asfotase alfa was not sufficient to treat the skeletal manifestations of HPP in our patient, indicating that some perinatal HPP patients should be treated with higher doses to reach treatment goals. Although bone disease and patient outcomes have been improved with tailored drug doses, neurological manifestations of HPP remain challenging.

Rhabdomyolysis is an acute failure of cellular homeostasis resulting in muscle breakdown, triggered by trauma, infection, drugs or strenuous exercise. Recurrent rhabdomyolysis is often associated with genetic and metabolic defects of skeletal muscle. The sarcoendoplasmic reticulum Ca2+-ATPase 2 (SERCA2), encoded by the ATP2A2 gene, is an intracellular pump located in the sarcoplasmic and endoplasmic reticulum that is essential for maintaining intracellular calcium (Ca2+) homeostasis and is highly expressed in slow-twitch muscle. Heterozygous loss-of-function variants in ATP2A2 have previously been associated with dominant skin diseases, but not with rhabdomyolysis. In this study, we report a rare novel heterozygous missense variant in the ATP2A2 gene (c.1583G>A, p.R528Q) identified in 14 affected individuals from three unrelated families with recurrent rhabdomyolysis. Muscle biopsy revealed mild myopathic changes with fibre type uniformity, core-like structures and Z-band streaming, but normal levels of SERCA2 protein. Ca2+ imaging showed that sarcoplasmic reticulum Ca2+ reuptake mediated by SERCA was significantly slower in myotubes derived from patient fibroblasts carrying the c.1583G > A variant. We hypothesize that the ATP2A2 variant impairs SERCA2a function in slow-twitch muscle, disrupting SR Ca2+ reuptake and causing cytosolic Ca2+ overload following a trigger, leading to recurrent rhabdomyolysis. Morphant zebrafish embryos with atp2a2a knockdown showed morphological and functional muscle abnormalities, with a reduction in body length and trunk muscle area associated with a reduction in locomotor activity in zebrafish larvae. Co-injection of wild-type human SERCA2a mRNA, but not variant SERCA2a mRNA, resulted in complete rescue of the phenotype. This study reveals a novel association between a heterozygous ATP2A2 variant and autosomal dominant recurrent rhabdomyolysis. Both in vitro and in vivo studies provide evidence that the variant alters SERCA2 function, causing abnormal intracellular Ca2+ homeostasis in skeletal muscle, resulting in rhabdomyolysis. The work not only increases understanding of autosomal dominant rhabdomyolysis but also provides a diagnostic conclusion for three generations of affected individuals across the three families.

Background: Lynch syndrome (LS) is a cancer-susceptibility syndrome associated with autosomal dominant predisposition to a spectrum of cancers, primarily of the colorectum and endometrium, which exhibit impaired DNA mismatch repair (MMR) activity. LS is caused by a hereditary (germline) pathogenic (PV) or likely pathogenic variant (LPV) in one of the mismatch repair (MMR) genes—MLH1, MSH2, MSH6, PMS2, or EPCAM. Although point mutations are the most common genetic changes in MMR genes, >20% are large genomic rearrangements. We hypothesized that a two-tier diagnostic strategy for Lynch syndrome (LS) using next generation sequencing (NGS) and multiplex ligation-dependent probe amplification (MLPA) can increase diagnostic yield of patients with Lynch syndrome. Methods: This study included 60 patients suspected of LS. After genetic counseling, they were referred to genetic testing. Genomic DNA was extracted from peripheral blood and sequenced using NGS multigene panel testing covering 113 cancer susceptibility genes, including MMR genes. Regarding limitations of NGS analysis, which cannot reliably detect genomic alterations larger than 50 base pairs in length, the MLPA method was used for NGS negative DNA samples in order to identify larger deletions and duplications, commonly referred to as copy number variations (CNVs). Results: Different PVs were detected by NGS in 10 patients and CNVs were detected by MLPA in 7 more patients: 3xMLH1 del ex9-15, 2xMSH2 del ex1 and upstream, 1xMSH2 del ex9, and 1xMSH2 del ex1. We did not detect LPVs or variants of uncertain significance (VUS). In our cohort, the addition of MLPA provided an incremental yield of seven pathogenic CNVs, representing an 11.6% absolute increase in diagnostic sensitivity (from 16.7% to 28.3%) over the NGS-alone workflow, with CNVs accounting for 41% of all pathogenic findings. Conclusions: Our results show that MLPA is a very useful method in molecular diagnostics of LS and its implementation in routine genetic testing in combination with NGS using multigene panel testing would benefit both patients and health care providers.

Racionalno indiciranje metaboličkih pretraga ključna je sastavnica uspješne dijagnostike nasljednih metaboličkih bolesti.Ono uključuje dobar odabir pretraga, njihov optimalan redoslijed i pravo vrijeme početka.Za ostvarenje toga nužno je imati specifična znanja što

By anchoring different cell structures like Z-bands, mitochondria, and desmosomes to the cytoskeleton, desmin filaments are essential for cellular integrity, signal transduction and mitochondrial function. The spectrum of clinical phenotypes associated with DES gene mutations is wide and heterogeneous. The most common clinical presentations of desminopathy include cardiomyopathy, cardiac conduction disease, and progressive skeletal myopathy. We present a case of an 11-year-old girl with progressive dilated cardiomyopathy (DCM) needing ECMO treatment. ECMO treatment was complicated by the early development of intracardiac thrombi and lung necrosis. Post-mortem exome sequencing revealed the causative, previously unreported, de novo mutation of DES gene, c.365 A > C, p.Tyr122Ser, characterized with unusually progressive clinical course leading to death.

Background Somatic and germline genetic alterations are significant drivers of cancer. Increasing integration of new technologies which profile these alterations requires timely, equitable and high-quality genetic counselling to facilitate accurate diagnoses and informed decision-making by patients and their families in preventive and clinical settings. This article aims to provide an overview of genetic counselling legislation and practice across European Union (EU) Member States to serve as a foundation for future European recommendations and action.Methods National legislative databases of all 27 Member States were searched using terms relevant to genetic counselling, translated as appropriate. Interviews with relevant experts from each Member State were conducted to validate legislative search results and provide detailed insights into genetic counselling practice in each country.Results Genetic counselling is included in national legislative documents of 22 of 27 Member States, with substantial variation in legal mechanisms and prescribed details (i.e. the 'who, what, when and where' of counselling). Practice is similarly varied. Workforce capacity (25 of 27 Member States) and genetic literacy (all Member States) were common reported barriers. Recognition and/or better integration of genetic counsellors and updated legislation and were most commonly noted as the 'most important change' which would improve practice.Conclusions This review highlights substantial variability in genetic counselling across EU Member States, as well as common barriers notwithstanding this variation. Future recommendations and action should focus on addressing literacy and capacity challenges through legislative, regulatory and/or strategic approaches at EU, national, regional and/or local levels.

Dihydrolipoamide dehydrogenase (DLD) deficiency can, in one of its forms, be a rare cause of acute liver failure. Clinical presentation is nonspecific. Biochemical findings can reflect metabolic block, but vary depending on patient and his condition. Consensus treatment guidelines do not exist. We present a family with five members suffering from DLD deficiency. Patient 1 presented with emesis, mental deterioration, and fulminant hepatic failure, which required high-urgency liver transplantation. His younger brother, patient 2, experienced unexplained hypoglycemia and metabolic acidosis on the second day after cardiac surgery. Three affected younger siblings were asymptomatic. In patients with acute liver failure of unknown etiology urgent metabolic work-up should be done, and whole exome sequencing considered. Liver transplantation remains life-saving treatment option, but its outcome may be dependent on etiology-specific supportive treatment.

Huppke-Brendel syndrome (HBS) is an autosomal recessive disorder caused by SLC33A1 mutations, a gene coding for the acetyl-CoA transporter-1 (AT-1). So far it has been described in nine pediatric and one adult patient. Therapeutic trials with copper histidinate failed to achieve any clinical improvement. Here, we describe the clinical characteristics of two novel patients, one of them diagnosed by gene analysis and his sib postmortally based on clinical characteristics. We demonstrate a therapeutic trial with acetylation therapy, consisting of N-acetylcysteine and ketogenic diet, in one of them. We provide biochemical data on N-acetylated amino acids in cerebrospinal fluid (CSF) and plasma before and after starting this treatment regimen. Our results indicate that ketogenic diet and N-acetylcysteine do not seem to normalize the concentrations of N-acetylated amino acids in CSF or plasma. The overall metabolic pattern shows a trend toward lowered levels of N-acetylated amino acids in CSF and to a lesser extent in plasma. Although there are some assumptions, the function of AT-1 is still not clear and further studies are needed to better understand mechanisms underlying this complex disorder.

Genske analize omogućuju definiranje molekularne osnove nasljedne metaboličke bolesti,

Contactin-associated protein-like 2 ( CNTNAP2 ) gene encodes for CASPR2, a presynaptic type 1 transmembrane protein, involved in cell–cell adhesion and synaptic interactions. Biallelic CNTNAP2 loss has been associated with “Pitt-Hopkins-like syndrome-1” (MIM#610042), while the pathogenic role of heterozygous variants remains controversial. We report 22 novel patients harboring mono- ( n = 2) and bi-allelic ( n = 20) CNTNAP2 variants and carried out a literature review to characterize the genotype–phenotype correlation. Patients (M:F 14:8) were aged between 3 and 19 years and affected by global developmental delay (GDD) ( n = 21), moderate to profound intellectual disability ( n = 17) and epilepsy ( n = 21). Seizures mainly started in the first two years of life (median 22.5 months). Antiseizure medications were successful in controlling the seizures in about two-thirds of the patients. Autism spectrum disorder (ASD) and/or other neuropsychiatric comorbidities were present in nine patients (40.9%). Nonspecific midline brain anomalies were noted in most patients while focal signal abnormalities in the temporal lobes were noted in three subjects. Genotype–phenotype correlation was performed by also including 50 previously published patients (15 mono- and 35 bi-allelic variants). Overall, GDD ( p < 0.0001), epilepsy ( p < 0.0001), hyporeflexia ( p = 0.012), ASD ( p = 0.009), language impairment ( p = 0.020) and severe cognitive impairment ( p = 0.031) were significantly associated with the presence of biallelic versus monoallelic variants. We have defined the main features associated with biallelic CNTNAP2 variants, as severe cognitive impairment, epilepsy and behavioral abnormalities. We propose CASPR2-deficiency neurodevelopmental disorder as an exclusively recessive disease while the contribution of heterozygous variants is less likely to follow an autosomal dominant inheritance pattern.

Glycosylphosphatidylinositol anchoring disorders (GPI-ADs) are a subgroup of congenital disorders of glycosylation. GPI biosynthesis requires proteins encoded by over 30 genes of which 24 genes are linked to neurodevelopmental disorders. Patients, especially those with PIGA-encephalopathy, have a high risk of premature mortality which sometimes is attributed to cardiomyopathy. We aimed to explore the occurrence of cardiomyopathy among patients with GPI-ADs and to raise awareness about this potentially lethal feature. Unpublished patients with genetically proven GPI-ADs and cardiomyopathy were identified through an international collaboration and recruited through the respective clinicians. We also reviewed the literature for published patients with cardiomyopathy and GPI-AD and contacted the corresponding authors for additional information. We identified four novel and unrelated patients with GPI-AD and cardiomyopathy. Cardiomyopathy was diagnosed before adulthood and was the cause of early demise in two patients. Only one patients underwent cardiac workup after being diagnosed with a GPI-AD. All were diagnosed with PIGA-encephalopathy and three had a disease-causing variant at the same residue. The literature reports five additional children with GPI-AD related cardiomyopathy, three of which died before adulthood. We have shown that patients with GPI-ADs are at risk of developing cardiomyopathy and that regular cardiac workup with echocardiography is necessary.

The aim of our study was to describe the characteristics of patients with classical galactosemia in Croatia, with the description of patients with galactokinase deficiency and a patient who was a double heterozygote for mutations of the galactose-1-phosphate uridyl transferase (GALT), and galactose-4’-epimerase (GALE) genes. The study included 24 patients who were diagnosed with classic galactosemia from 1977 to 2020. Diagnosis was based on clinical presentation and galactose concentrations in blood and urine, and confirmed by measuring galactose-1-phosphate-uridyl-transferase activity and/or GALT gene analysis. Acute manifestations of the disease developed in 87% of patients in the newborn period, and one patient died. The median age at the onset of first symptoms was four days and for onset of therapy 11.5 days. At least one long-term complication occured in 78.3% of patients, including developmental disorders (68.2%), behavioral disorders (31.8%), speech disorders (55.6%), impaired intellectual abilities (46.2%), other neurological complications (40.9%), cataract (18.2%), and decreased bone mineral density (27.8%). Ovarian insufficiency occured in 66.7% of female patients older than 10 years. When comparing siblings, although a galactose-free diet was started earlier in the second-born children with classical galactosemia, the incidence of long-term outcomes did not appear to be related to birth order. In conclusion, this study shows that the vast majority of patients develop symptoms in the neonatal period, as well as long-term complications, despite strict adherence to a galactose-free diet. Many factors that affect the pathogenesis and clinical course of the disease are still unknown, which is why further research into classical galactosemia is needed.