A study of Iraqi patients with homocysteine remethylation disorders in a tertiary pediatric centre

Background

Hyperhomocysteinemia is a group of inherited homocysteine metabolism disorders characterised by elevated blood homocysteine levels (total homocysteine >15 μM). Homocystinuria is classified into two main homocysteine metabolism disorders. Classical Homocystinuria is caused by a deficiency of the pyridoxine-dependent enzyme cystathionine beta-synthase in the trans‑sulfuration pathway. Non-classical Homocystinuria is a group of disorders affecting the interconversion of methionine to homocysteine through the re-methylation pathway.

Aim

This study aims to describe the clinical, biochemical, and genetic profiles of patients with re-methylation disorders.

Patients and methods

A cohort study was conducted at the metabolic clinic of Children Welfare Teaching Hospital in Baghdad from the 1st of December 2021 to the 1st of December 2022. The study included fifteen patients who met the following criteria: (1) elevated serum homocysteine levels (>15 μmol/L); (2) low or normal blood methionine levels (12-40 μmol/L). Results: fourteen MTHFR patients underwent statistical analysis, and one CblC patient was assessed separately. MTHFR patients comprised nine females and five males. The mean age at presentation was 7.1 years ±4.5, ranging from 1 to 16 years. Consanguineous marriages were reported in 13 patients. A family history of a similar disorder was documented in 73 % of cases. Among the families, four had two affected siblings. The two main reported clinical manifestations were gait disturbance (10/14, 71.4 %) and cognitive impairment/intellectual disability (6/14, 42.8 %). Brain MRI was conducted for all studied patients, with leukodystrophy being the most common finding (8/14, 57.1 %). Molecular testing revealed variants in MTHFR in 14 patients, and MMACHC in one patient.

Conclusion

According to this study, individuals with homocysteine re-methylation disorders can manifest symptomatology such as neuroregression, psychomotor delay, and whiter matter changes earlier than anticipated. And these disorders are amenable to treatment. Genetic testing is crucial in identifying the specific mutation type and guiding definitive treatment.

Subcutaneous vitamin B12 administration using a portable infusion pump in cobalamin-related remethylation disorders: a gentle and easy to use alternative to intramuscular injections

Background

Cobalamin (cbl)-related remethylation disorders are a heterogeneous group of inherited disorders comprising the remethylation of homocysteine to methionine and affecting multiple organ systems, most prominently the nervous system and the bone marrow. To date, the parenteral, generally intramuscular, lifelong administration of hydroxycobalamin (OHCbl) is the mainstay of therapy in these disorders. The dosage and frequency of OHCbl is titrated in each patient to the minimum effective dose in order to account for the painful injections. This may result in undertreatment, a possible risk factor for disease progression and disease-related complications.

Results

We describe parenteral administration of OHCbl using a subcutaneous catheter together with a portable infusion pump in a home therapy setting in four pediatric patients with remethylation disorders, two patients with cblC, one patient with cblG, and one patient with cblE deficiency, in whom intramuscular injections were not or no longer feasible. The placement of the subcutaneous catheters and handling of the infusion pump were readily accomplished and well accepted by the patients and their families. No adverse events occurred. The use of a small, portable syringe driver pump allowed for a most flexible administration of OHCbl in everyday life. The concentrations of total homocysteine levels were determined at regular patient visits and remained within the therapeutic target range. This approach allowed for the continuation of OHCbl therapy or the adjustment of therapy required to improve metabolic control in our patients.

Conclusions

Subcutaneous infusion using a subcutaneous catheter system and a portable pump for OHCbl administration in combined and isolated remethylation disorders is safe, acceptable, and effective. It decreases disease burden in preventing frequent single injections and providing patient independence. Thus, it may promote long-term adherence to therapy in patients and parents.

Molecular and biochemical investigations of inborn errors of metabolism-altered redox homeostasis in branched-chain amino acid disorders, organic acidurias, and homocystinuria

India, resembling other developing nations, is confronting a hastening demographic switch to non-communicable diseases. Inborn errors of metabolism (IEM) constitute a varied heterogeneous group of disorders with variable clinical appearance, primarily in the pediatric populace. Congenital deformities and genetic disorders are significant for mortality throughout the world, and the Indian scenario is not very different. IEMs are a group of monogenic issues described by dysregulation of the metabolic networks that bring about development and homeostasis. Incipient evidence focuses on oxidative stress and mitochondrial dysfunction as significant contributors to the multiorgan modifications are detected in a few IEMs. The amassing of toxic metabolites in organic acidurias, respiratory chain, and fatty acid oxidation ailments inhibit mitochondrial enzymes and processes, bringing about elevated levels of reactive oxygen species (ROS). In different IEMs, as in homocystinuria, various sources of ROS have been suggested. In patients' samples along with cellular and experimental animal models, a few investigations have recognized substantial increments in ROS levels alongside diminishes in antioxidant defenses, relating with oxidative damage to proteins, lipids as well as DNA. Elevated ROS levels interrupt redox signaling pathways controlling biological processes such as cell development, differentiation, or apoptosis; however, few investigations explore these processes in IEMs. This review depicts the mitochondrial dysfunction, oxidative stress, redox signaling in branched-chain amino acid disorders, further organic acidurias, and homocystinuria, alongside the latest research investigating the proficiency of antioxidants in addition to mitochondria-targeted therapies as therapeutic components in these diseases.