The diagnosis and treatment of rare diseases present significant global challenges. This study aimed to identify the difficulties faced by specialists in the diagnosis and management of rare diseases, as well as to gather their recommendations for potential solutions. An expert committee specializing in inborn metabolic disease and genetics developed a comprehensive survey, which was then distributed online to professionals working with rare diseases. A total of 21 specialists actively engaged in the management of rare diseases participated in the survey. All participants acknowledged the substanstial significant diagnostic challenges associated with rare diseases, with 86% indicating that these diagnostic challenges negatively affect their clinical practice. The primary obstacles encountered in the diagnosis and follow-up of rare diseases were low awareness, a lack of a multidisciplinary approach, insufficient numbers of specialists and inadequate infrastructure, limited newborn screening programs, challenges in accessing treatment, and insufficient psychosocial support. All participants emphasized the need for a multidisciplinary approach in the management of rare diseases. Proposed solutions included enhanced training for healthcare professionals, the establishment of multidisciplinary teams and diagnostic algorithms, the regular convening of councils and meetings, and the establishment of robust registries. While all participants rated their own clinical experience as proficient in diagnosing and treating rare diseases, the establishment of multidisciplinary teams was the most frequently suggested area for improvement. Conclusion: Addressing the challenges in the diagnosis, treatment, and monitoring of rare diseases requires a multifaceted approach, including raising awareness, enhancing patient services, developing robust research and improving the infrastructure, establishing multidisciplinary care frameworks, and implementing preventive medicine and social policies. What is Known:• It is estimated that over 300 million people globally are living with one or more rare diseases. The process of diagnosis, treatment, and follow-up of rare diseases involves significant global challenges. What is New:• In our study, the difficulties encountered by specialists in the diagnosis and treatment of rare diseases in Türkiye and solution suggestions are presented. This is the first study on this subject in Türkiye.

Objectives DNAJC12 deficiency (OMIM# 617384) is a new cause of hyperphenylalaninemia (HPA). The deficiency of the co-chaperone protein DNAJC12 was identified in 2017. To date, only 43 patients have been reported. Here, we report four patients from a single family with DNAJC12 deficiency while being followed up with a diagnosis of HPA. Case presentation Two of the patients, who were cousins, were diagnosed with HPA by newborn screening. And the other two patients were siblings of these patients. Neurological examinations were normal except for one patient with mild learning disability. A c.158-2A>T p.(?) biallelic pathogenic variant was detected in intron 2 of the DNAJC12 gene. In the 24 h tetrahydrobiopterin (BH4) challenge test, there was a significant decrease in phenylalanine levels, especially at the 16th hour. Three patients had decreased homovalinic acid (HVA) and 5-hydroxyindoleacetic acid (5HIAA) in cerebrospinal fluid (CSF), while only one had decreased 5HIAA. In treatment, sapropterin, levodopa/carbidopa and 5-OH tryptophan were started. Conclusions We propose that it will be beneficial to evaluate the patients who have unexplained hyperphenylalaninemia for DNAJC12 deficiency. Patients with early diagnosis of neurotransmitter deficiency may be given a chance to be treated before clinical symptoms begin.

Background/Objectives: Phenylketonuria is a hereditary metabolic disorder characterized by a deficiency of phenylalanine hydroxylase. The main treatment for PKU is a phenylalanine-restricted diet. The exclusion of protein rich natural foods and inclusion of low-Phe substitutes may give rise to an imbalanced diet, and the increased risk of overweight and obesity in PKU is a cause for concern. We aimed to evaluate the body composition and nutritional biochemical biomarkers in adult PKU patients who are on Phe-restricted and essential amino acid-supplemented nutrition therapy and to investigate the relationships between these parameters and patient gender, adherence to dietary therapy, and disease type, defined as mild or classic PKU. Methods: The study group comprised 37 PKU patients and 26 healthy siblings as controls. The participants were assessed based on an analysis of anthropometric parameters, body composition, and biochemical test results. Results: PKU patients do not have a higher incidence of overweight and obesity than healthy controls, the proportion of energy derived from carbohydrates in their diets was below the recommended level, and their total energy intake was below the recommended daily allowance. It was remarkable that patients with a treatment adherence ratio of <50% displayed a higher prevalence of overweight and abdominal obesity in comparison to those with a more favorable treatment adherence ratio. Conclusions: In view of the growing prevalence of overweight in the general population, PKU patients should be kept under close long-term follow-up. Particularly in the group with low treatment compliance, more caution should be taken in terms of adverse outcomes.

Objectives: Transient infantile hypertriglyceridemia (HTGTI) is caused by mutations in the glycerol-3-phosphate dehydrogenase 1 (GPD1) gene. HTGTI is characterized by hypertriglyceridemia, hepatomegaly, hepatic steatosis and fibrosis in infancy. Here, we reported first Turkish HTGTI patient with a novel mutation of GPD1, having hypertriglyceridemia, hepatomegaly, growth retardation and hepatic steatosis. He is the first case who needs transfusion until 6th month in GPD1. Case presentation: A 2-month-27-day-old boy, who had growth retardation, hepatomegaly and anemia suffered to our hospital with vomiting. Triglyceride level was 1603 mg/dL (n<150). Liver transaminases were elevated and hepatic steatosis was developed. He needed transfusion with erythrocyte suspension until 6th month. Etiology could not be elucidated by clinical and biochemical parameters. A novel homozygous c.936_940del (p.His312GlnfsTer24) variant was detected in the GPD1 gene by Clinical Exome Analysis. Conclusions: GPD1 deficiency should be investigated in the presence of unexplained hypertriglyceridemia and hepatic steatosis in children especially in infants.

Background/Objectives: Phenylketonuria is a hereditary metabolic disorder characterized by a deficiency of phenylalanine hydroxylase. Main treatment for PKU is a phenylalanine-restricted diet. Exclusion of protein rich natural foods and inclusion of low-Phe substitutes may give rise to an imbalanced diet increasing the risk of overweight and obesity in PKU is a cause of concern. We aimed to evaluate the body composition and nutritional biochemical biomarkers in adult PKU patients who are on Phe-restricted and essential amino acids supplemented nutrition therapy and to investigate the relationships, between these parameters and patient gender, adherence to dietary therapy and disease type defined as mild or classic PKU. Methods: The study group comprised 37 PKU patients and 26 healthy siblings as controls. The participants were assessed based on an analysis of anthropometric parameters, body composition and biochemical test results. Results: PKU patients do not have a higher incidence of overweight and obesity than healthy controls, and the proportion of energy derived from carbohydrates in their diets was below the recommended level, and the total energy intake was below the recommended daily allowance. It was remarkable that patients with a treatment adherence ratio of <50% displayed a higher prevalence of overweight and abdominal obesity in comparison to those with a more favorable treatment adherence ratio. Conclusions: In view of the growing prevalence of overweight in the general population, PKU patients should be kept under close long-term follow-up. Particularly in the group with low treatment compliance, more caution should be paid in terms of adverse outcomes.

Background: Phenylketonuria (PKU) requires lifelong phenylalanine (Phe) restriction, potentially affecting dietary inflammatory potential. We investigated the relationships between the Dietary Inflammatory Index (DII), circulating cytokines, and metabolic parameters in adolescents with PKU. Methods: This case–control study enrolled 61 adolescents with PKU (aged 10–18 years) and 61 healthy age- and sex-matched controls. DII scores were calculated from three-day dietary records using 22 available dietary parameters. Anthropometric measurements, bioelectrical impedance analysis, biochemical markers, blood Phe concentrations, and pro-inflammatory and anti-inflammatory cytokines (GM-CSF, IFN-γ, TNF-α, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12 (p70), IL-13) were assessed. IL-4 was excluded from analysis because of analytical concerns. Between-group cytokine comparisons were evaluated using Bonferroni correction, and within-group correlation analyses and exploratory multivariable regression analyses were performed. Results: DII scores were significantly lower in the PKU group than in controls (−1.83 ± 1.35 vs. 0.71 ± 1.39; p < 0.001), with negative scores in 93.4% of adolescents with PKU. GM-CSF, TNF-α, IL-1β, and IL-12 (p70) concentrations were nominally higher in PKU (unadjusted p = 0.006–0.023; r = 0.206–0.247), but none remained significant after Bonferroni correction (threshold p < 0.00417). In exploratory adjusted regression analyses, DII was not significantly associated with the four selected cytokines, whereas the study group showed a nominal association with TNF-α (p = 0.007). Within-group analyses showed no significant correlations between DII scores and GM-CSF, TNF-α, IL-1β, or IL-12 (p70) concentrations in either group. Conclusions: Adolescents with PKU exhibited more anti-inflammatory dietary scores than healthy controls, but cytokine differences did not withstand correction for multiple comparisons. These exploratory findings warrant confirmation in larger studies.