Histologically atypical case of Gaucher disease type 1.

This report presents a case of childhood Gaucher disease type 1, a rare inherited metabolic disorder. Although the clinical symptoms were classical, the histological findings in this case were atypical and initially led to diagnostic uncertainty. The pathognomonic histological finding on bone marrow is Gaucher cells, which are lipid-engorged phagocytes secondary to the accumulation of glucosylceramide. These cells typically demonstrate diffuse and avid iron staining using a Prussian blue iron stain. In this case, although the histiocytes seen on bone marrow were abnormal, the absence of iron staining on bone marrow led to a large range of other diagnoses being considered. In retrospect, this anomaly was likely in the setting of prolonged iron deficiency and anaemia as a result of the insidious nature of this presentation. The prognosis of type 1 Gaucher disease is favourable, with current treatments significantly improving duration and quality of life. We explore the utility of a collaborative multidisciplinary approach in addressing diagnostic uncertainty and the importance in making a diagnosis for Gaucher disease type 1 in order to provide appropriate and targeted treatment.

Interstitial lung disease and pancreatic exocrine insufficiency in CADDS: Phenotypic expansion and literature review.

Contiguous ABCD1/ DXS1357E deletion syndrome (CADDS) is a rare deletion syndrome involving two contiguous genes on Xq28, ABCD1 and BCAP31 (formerly known as DXS1357E). Only nine individuals with this diagnosis have been reported in the medical literature to date. Intragenic loss-of-function variants in BCAP31 cause the deafness, dystonia, and cerebral hypomyelination syndrome (DDCH). Isolated pathogenic intragenic variants in ABCD1 are associated with the most common peroxisomal disorder, X-linked adrenoleukodystrophy (X-ALD), a single transporter deficiency, which in its more severe cerebral form is characterised by childhood-onset neurodegeneration and high levels of very-long-chain fatty acids (VLCFA). While increased VLCFA levels also feature in CADDS, the few patients described to date all presented as neonates with a severe phenotype. Here we report a tenth individual with CADDS, a male infant with dysmorphic facial features who was diagnosed through ultra-rapid whole genome sequencing (WGS) in the setting of persistent cholestatic liver disease, sensorineural hearing loss, hypotonia and growth failure and developmental delay. Biochemical studies showed elevated VLCFA and mildly reduced plasmalogens. He died at 7 months having developed pancreatic exocrine deficiency and interstitial lung disease, two features we propose to be possible extensions to the CADDS phenotype. We also review the genetic, phenotypic, and biochemical features in previously reported individuals with CADDS.

A serendipitous journey to a promoter variant: The c.-106C>A variant and its role in late-onset ornithine transcarbamylase deficiency.

Ornithine transcarbamylase deficiency (OTCD) is an X-linked urea cycle disorder characterised by reduced or absent OTC enzyme activity, resulting in the accumulation of neurotoxic ammonia. Approximately 80%-90% of the causative variants are identified by Sanger sequencing or multiplex ligation-dependent probe amplification (MLPA) of the OTC gene. A 23-year-old male with biochemical evidence of OTCD was referred for molecular analysis. Initial Sanger sequencing yielded no pathogenic variants. MLPA testing raised suspicion of a mosaic deletion of exon 1; however, high-resolution microarray did not identify a copy number variant on the X chromosome. Sequencing over the suspected breakpoint detected a hemizygous likely pathogenic promoter variant, c.-106C > A, which was located within the MLPA probe binding site. Subsequently, historical patients referred to our centre, without a molecular aetiology for their OTCD, were re-sequenced with these primers and this variant was also identified in two additional unrelated males. All three patients described in this case series have the late-onset disease. Two presented at 5 years of age with vomiting, whilst the other was managed from birth based on a family history of late-onset OTCD. One patient required liver transplantation due to recurrent decompensations; the other two are managed with a protein-restricted diet. All three patients have not sustained any significant neurological insults and are functioning well as adults. These cases support screening of the promoter region within the OTC gene, particularly if a molecular basis has not been elucidated by MLPA or sequencing of the coding regions.

Understanding the role of SGLT2 inhibitors in glycogen storage disease type Ib: the experience of one UK centre.

BACKGROUND: Glycogen storage disease type Ib (GSD Ib) is a severe disorder of carbohydrate metabolism due to bi-allelic variants in SLC37A4. It is associated with neutropaenia and neutrophil dysfunction, which has recently been attributed to the accumulation of 1,5-anhydroglucitol-6-phosphate (1,5AG6P) within neutrophils. Treatment with sodium-glucose co-transporter-2 (SGLT2) inhibitors, such as empagliflozin, is a novel therapy that reduces 1,5-anhydroglucitol (1,5AG) in plasma. RESULTS: We report our experience in treating 8 paediatric GSD Ib patients with empagliflozin with a cumulative treatment time greater than 12 years. Treatment with a median dose of 5 mg (0.22 mg/kg height weight) of empagliflozin resulted in improvement in bowel health, growth, and laboratory parameters. Plasma 1,5AG levels reduced by a median of 78%. Baseline 1,5AG levels in our cohort were higher than in adult patients with GSD Ib. Hypoglycaemia on empagliflozin treatment occurred in 50% of our cohort. CONCLUSION: We report the largest single centre cohort of GSD Ib patients treated with empagliflozin to date. Treatment with SGLT2 inhibitors is a novel and favourable treatment option for neutropaenia and neutrophil dysfunction in GSD Ib. We suggest a low starting dose of empagliflozin with careful titration due to the risk of hypoglycaemia. The interpretation of 1,5AG levels and their role in treatment monitoring is yet to be established, and requires ongoing research.

Efficacy and safety of empagliflozin in glycogen storage disease type Ib: Data from an international questionnaire.

PURPOSE: This paper aims to report collective information on safety and efficacy of empagliflozin drug repurposing in individuals with glycogen storage disease type Ib (GSD Ib). METHODS: This is an international retrospective questionnaire study on the safety and efficacy of empagliflozin use for management of neutropenia/neutrophil dysfunction in patients with GSD Ib, conducted among the respective health care providers from 24 countries across the globe. RESULTS: Clinical data from 112 individuals with GSD Ib were evaluated, representing a total of 94 treatment years. The median age at start of empagliflozin treatment was 10.5 years (range = 0-38 years). Empagliflozin showed positive effects on all neutrophil dysfunction-related symptoms, including oral and urogenital mucosal lesions, recurrent infections, skin abscesses, inflammatory bowel disease, and anemia. Before initiating empagliflozin, most patients with GSD Ib were on G-CSF (94/112; 84%). At the time of the survey, 49 of 89 (55%) patients previously treated with G-CSF had completely stopped G-CSF, and another 15 (17%) were able to reduce the dose. The most common adverse event during empagliflozin treatment was hypoglycemia, occurring in 18% of individuals. CONCLUSION: Empagliflozin has a favorable effect on neutropenia/neutrophil dysfunction-related symptoms and safety profile in individuals with GSD Ib.

Ethylmalonic encephalopathy masquerading as meningococcemia.

Ethylmalonic encephalopathy (MIM #602473) is a rare autosomal recessive metabolic condition caused by biallelic variants in ETHE1 (MIM #608451), characterized by global developmental delay, infantile hypotonia, seizures, and microvascular damage. The microvascular changes result in a pattern of relapsing spontaneous diffuse petechiae and purpura, positional acrocyanosis, and pedal edema, hemorrhagic suffusions of mucous membranes, and chronic diarrhea. Here, we describe an instructive case in which ethylmalonic encephalopathy masqueraded as meningococcal septicemia and shock. Ultrarapid whole-genome testing (time to result 60 h) and prompt biochemical analysis facilitated accurate diagnosis and counseling with rapid implementation of precision treatment for the metabolic crisis related to this condition. This case provides a timely reminder to consider rare genetic diagnoses when atypical features of more common conditions are present, with an early referral to ensure prompt biochemical and genomic diagnosis.

The natural history of glycogen storage disease type Ib in England: A multisite survey.

Glycogen storage disease type Ib (GSDIb) is characterized by hepatomegaly and fasting hypoglycaemia as well as neutropaenia and recurrent infections. We conducted a retrospective observational study on a cohort of patients with GSDIb across England. A total of 35 patients, with a median age of 9.1 years (range 1-39 years), were included in the study. We examined the genotype and phenotype of all patients and reported 14 novel alleles. The phenotype of GSDIb in England involves a short fasting tolerance that extends into adulthood and a high prevalence of gastrointestinal symptoms. Growth is difficult to manage and neutropaenia and recurrent infections persist throughout life. Liver transplantation was performed in nine patients, which normalized fasting tolerance but did not correct neutropaenia. This is the first natural history study on the cohort of GSDIb patients in England.

New insights into carnitine-acylcarnitine translocase deficiency from 23 cases: Management challenges and potential therapeutic approaches.

Carnitine acyl-carnitine translocase deficiency (CACTD) is a rare autosomal recessive disorder of mitochondrial long-chain fatty-acid transport. Most patients present in the first 2 days of life, with hypoketotic hypoglycaemia, hyperammonaemia, cardiomyopathy or arrhythmia, hepatomegaly and elevated liver enzymes. Multi-centre international retrospective chart review of clinical presentation, biochemistry, treatment modalities including diet, subsequent complications, and mode of death of all patients. Twenty-three patients from nine tertiary metabolic units were identified. Seven attenuated patients of Pakistani heritage, six of these homozygous c.82G>T, had later onset manifestations and long-term survival without chronic hyperammonemia. Of the 16 classical cases, 15 had cardiac involvement at presentation comprising cardiac arrhythmias (9/15), cardiac arrest (7/15), and cardiac hypertrophy (9/15). Where recorded, ammonia levels were elevated in all but one severe case (13/14 measured) and 14/16 had hypoglycaemia. Nine classical patients survived longer-term-most with feeding difficulties and cognitive delay. Hyperammonaemia appears refractory to ammonia scavenger treatment and carglumic acid, but responds well to high glucose delivery during acute metabolic crises. High-energy intake seems necessary to prevent decompensation. Anaplerosis utilising therapeutic d,l-3-hydroxybutyrate, Triheptanoin and increased protein intake, appeared to improve chronic hyperammonemia and metabolic stability where trialled in individual cases. CACTD is a rare disorder of fatty acid oxidation with a preponderance to severe cardiac dysfunction. Long-term survival is possible in classical early-onset cases with long-chain fat restriction, judicious use of glucose infusions, and medium chain triglyceride supplementation. Adjunctive therapies supporting anaplerosis may improve longer-term outcomes.

Pathogenic variants in glutamyl-tRNAGln amidotransferase subunits cause a lethal mitochondrial cardiomyopathy disorder.

Mitochondrial protein synthesis requires charging mt-tRNAs with their cognate amino acids by mitochondrial aminoacyl-tRNA synthetases, with the exception of glutaminyl mt-tRNA (mt-tRNAGln). mt-tRNAGln is indirectly charged by a transamidation reaction involving the GatCAB aminoacyl-tRNA amidotransferase complex. Defects involving the mitochondrial protein synthesis machinery cause a broad spectrum of disorders, with often fatal outcome. Here, we describe nine patients from five families with genetic defects in a GatCAB complex subunit, including QRSL1, GATB, and GATC, each showing a lethal metabolic cardiomyopathy syndrome. Functional studies reveal combined respiratory chain enzyme deficiencies and mitochondrial dysfunction. Aminoacylation of mt-tRNAGln and mitochondrial protein translation are deficient in patients' fibroblasts cultured in the absence of glutamine but restore in high glutamine. Lentiviral rescue experiments and modeling in S. cerevisiae homologs confirm pathogenicity. Our study completes a decade of investigations on mitochondrial aminoacylation disorders, starting with DARS2 and ending with the GatCAB complex.