Testing Modalities for Inborn Errors of Metabolism — What a Clinician Needs to Know?

Knowledge and experiences of healthcare workers in managing children with neurometabolic disorders in a developing country: a cross-sectional study

OBJECTIVE

To evaluate the knowledge and experiences of healthcare workers in the management of neurometabolic disorders.

METHODS

A cross-sectional study was carried out among the 132 participants of a continued medical education program conducted in the Department of Pediatrics at a tertiary-care teaching hospital. A questionnaire-based feedback form was circulated among the participants, and their responses were analyzed.

RESULTS

Ninety-three responses were analyzed. The most common pediatric illnesses identified were infections (91%), nutritional (91%), birth-related injuries (44.4%) and metabolic disorders (44.4%). Consanguinity (81.5%) and genetic heterogeneity (42.4%) were recognized as most important causes of neurometabolic disorders. Important steps identified for prevention were prenatal testing (65.6%) and newborn screening at birth (61%); while for improving the diagnosis were routine availability of metabolic investigations (65.3%) and screening at birth (46.6%). Most respondents (58.7%) expressed discomfort in managing a case with inherited metabolic defect due to a lack of knowledge (46.8%) and diagnostic facilities (44.6%). Despite access to testing in the majority, a high cost of testing was noticed for biochemical and genetic investigations. The majority of participants (73%) considered some of the inherited metabolic disorders as treatable. Dietary substitution (89.3%), enzyme replacement (69%), cofactor replacement (53.6%), gene therapy (35.7%) and regular dialysis (16.7%) were considered the treatment options.

CONCLUSION

In spite of growing awareness of inherited metabolic disorders, there are still gaps in knowledge among healthcare workers. It is challenging to diagnose and manage these disorders. Cost-reduction of diagnostic tests, routine newborn screening and increased educational activities are key challenges to be addressed.

Detection of IEMs by Mass Spectrometry Techniques in High-Risk Children: A Pilot Study

OBJECTIVES

To determine the incidence and types of inborn errors of metabolism (IEMs) in high-risk children using mass spectrometry techniques.

METHODS

Children considered high-risk for IEM were screened for metabolic diseases during a 3-y period. Dried blood spots and urine samples were analyzed by tandem mass spectrometry (LC-MS/MS) and gas chromatograph-mass spectrometry (GCMS). Samples with abnormal amino acids were confirmed by high-performance liquid chromatography (HPLC).

RESULTS

Eight hundred and twenty-two suspected cases were evaluated; of which, 87 possible cases of IEMs were identified. Homocystinuria (n = 51) was the most common IEM detected followed by biotinidase deficiency (n = 7), glutaric aciduria type 1 (n = 7), and carnitine uptake defect (n = 6). Overall, there were 45 (51.7%) cases of organic acidemia, 31 cases (35.6%) of amino acid defect, 9 (10.3%) cases of fatty-acid oxidation disorders, and 2 (2.3%) cases of probable mitochondrial disorder.

CONCLUSION

IEMs are common in India, with a hospital-based incidence of 1 in approximately 6642 among high-risk children. Screening of high-risk children by mass spectrometry techniques is a valuable strategy for early diagnosis of IEMs where universal newborn screening is not yet available.

Spectrum of Common and Rare Small Molecule Inborn Errors of Metabolism Diagnosed in a Tertiary Care Center of Maharashtra, India

Introduction

Inborn errors of metabolism (IEM) form a large group of genetic diseases involving defects in genes coding for enzymes, receptors, and cofactors in the metabolic pathways of small and large molecules. The present study is the comprehensive data analysis of the tandem mass spectrometry (TMS) and urine metabolic pattern for the diagnosis of IEMs by gas chromatography and mass spectrometry (GC/MS) in samples received for high-risk IEM screening.

Methods

We conducted a retrospective analysis of children diagnosed with IEMs presenting at the genetic clinic of Mahatma Gandhi Missions (MGM) Medical College, Aurangabad. This article summarizes retrospective data of 40 pediatric cases over a three-year period, diagnosed with small molecule IEM based on the standard testing criteria.

Results

Out of 40, 17 patients (42.5%) were found to have organic acidemias, four (10%) had fatty acid oxidation defects, six (15%) had disorders of aminoacidopathies, seven (17.5%) had mitochondrial diseases, and three (7.5%) had urea cycle defects. One patient in each group (2.5% each) had carbohydrate metabolism defects, purine metabolic defects, and neurotransmitter metabolic defects.

Conclusions

This clinico-etiological profile study has thrown light on the clinical features and natural course of many common and rare IEMs, and it may provide clinicians with a deeper understanding of these conditions, allowing for improved early diagnosis and treatment of these diseases. Because of the high degree of consanguinity and marriages in the same community, common as well as many rare inherited metabolic diseases were diagnosed and novel genetic variants were identified.

Inborn Errors of Metabolism-Approach to Diagnosis and Management in Neonates

Inborn errors of metabolism (IEM), otherwise known as inherited metabolic disorders (IMD), are individually rare, but collectively common. IEM pose a challenge to diagnosis, as neonates present with nonspecific signs. A high index of suspicion is essential. Knowledge on clinical presentation may be life saving, especially for conditions that are treatable. It is important for the first-line physicians not to miss treatable disorders. Simplified classification and algorithmic approach help in the clinical setting. This article describes the classification of IEM into three groups, namely group 1 - intoxication disorders, group 2 - energy defects, and group 3 - storage disorders. Clinical presentations of IEM in the neonatal period, a quick guide to the diagnosis with the help of baseline investigations (glucose, arterial blood gas, lactate, ammonia, and ketone abbreviated as GALAK), a tabulated guide to the diagnosis with the help of tandem mass spectrometry (TMS), and gas chromatography and mass spectrometry (GCMS) are summarized in this article. Four principles of therapy that include substrate reduction, provision of deficient metabolites, disposal of toxic metabolites, and increase in enzyme activity are elaborated with particular stress to the diet management. In addition, a list of medications used in the treatment of different disorders classified according to Society for the Study of IEM (SSIEM) is presented.

Infantile Tremor Syndrome Followed by West Syndrome: Effect or Continuation of Spectrum?

BACKGROUND

Infantile tremor syndrome (ITS) is a nutritional deficiency syndrome, frequently reported from the Indian subcontinent caused by vitamin B12 deficiency. The West syndrome (WS), on the other hand, is a type of epileptic encephalopathy with variable etiology.

CASE SERIES

We present a series of five children who presented with symptoms consistent with ITS and received standard intramuscular vitamin B12 therapy to which good response was observed. All these children were readmitted with WS with a time lag varying from 2 to 12 months. Magnetic resonance imaging brain and metabolic screen were within normal limits. Three out of five patients responded well to adrenocorticotropic hormone (ACTH), remaining two required additional drugs. We hypothesize that WS could have developed after ITS due to developmental desynchronization.

CONCLUSION

In the Indian scenario, it is particularly important to be aware of appearance of WS after ITS, because of high prevalence of ITS and devastating nature of WS.