MADD-like pattern of acylcarnitines associated with sertraline use.

Multiple acyl-CoA dehydrogenase deficiency (MADD) is a primary mitochondrial dysfunction affecting mitochondrial fatty acid and protein metabolism, caused by biallelic pathogenic variants in ETFA, ETFB, or ETFDH genes. The heterogeneous phenotypes associated with MADD have been classified into three groups: neonatal onset with congenital anomalies (type 1), neonatal onset without congenital anomalies (type 2), and attenuated and/or later onset (type 3). Here, we present two cases with biochemical profiles mimicking late-onset MADD but negative genetic testing, associated with the use of sertraline, a commonly used antidepressant. Case 1 is a 22 yo woman diagnosed with depression and profound fatigue who was referred to the metabolic clinic because of carnitine deficiency and a plasma acylcarnitine profile with a MADD-like pattern. Case 2 is a 61 yo woman with a history of chronic fatigue who was admitted to the emergency department with difficulty swallowing, metabolic acidosis, and mild rhabdomyolysis. Plasma acylcarnitine profile showed a MADD-like pattern. The muscle biopsy revealed lipid droplet accumulation and proliferation of mitochondria with abnormal osmiophilic inclusions, and a biochemical assay of the respiratory chain showed a deficit in complex II activity. In both cases, urine organic acid profile was normal, and genetic tests did not detect variants in the genes involved in MADD. Sertraline was on their list of medications and considering its association with inhibition of mitochondrial function and rhabdomyolysis, the team recommended the discontinuation under medical supervision. In Case 1 after discontinuation, the plasma acylcarnitine test normalized, only to return abnormal when the patient resumed sertraline. In Case 2, after sertraline was discontinued rhabdomyolysis resolved, and the muscle biopsy and biochemical assay of the respiratory chain normalized. Although sertraline is considered a safe drug, these two cases suggest that the use of sertraline may be associated with a potentially reversible form of mitochondrial dysfunction mimicking MADD. Further studies are needed to confirm and estimate the risk of MADD-like presentations with the use of sertraline, as well as identifying additional contributing factors, including genetic factors. Metabolic physicians should consider sertraline use in the differential diagnosis of MADD, particularly when genetic testing is negative.

Ring Chromosome 14 with a Terminal 14q32.33 Deletion.

OBJECTIVES: Ring chromosome 14 is a rarely observed chromosomal abnormality characterized by a circular, ring-like appearance in one or both copies of chromosome 14. Ring chromosome 14 syndrome (OMIM #616606) is marked by global developmental delays, drug-resistant epilepsy, microcephaly, and ocular abnormalities. To date, fewer than 100 cases of ring chromosome 14 syndrome have been described in the medical literature. We describe a case of ring chromosome 14 and its clinical presentation in a 10-year-old female, adding to the literature about this rare condition.

De Novo Variants in RAB11B Cause Various Degrees of Global Developmental Delay and Intellectual Disability in Children.

BACKGROUND: RAB11B was described previously once with a severe form of intellectual disability. We aim at validation and delineation of the role of RAB11B in neurodevelopmental disorders. METHODS: We present seven novel individuals with disease-associated variants in RAB11B when compared with the six cases described in the literature. We performed a cross-sectional analysis to identify the clinical spectrum and the core phenotype. Additionally, structural effects of the variants were assessed by molecular modeling. RESULTS: Seven distinct de novo missense variants were identified, three of them recurrent (p.(Gly21Arg), p.(Val22Met), and p.(Ala68Thr)). Molecular modeling suggests that those variants either affect the nucleotide binding (at amino acid positions 21, 22, 33, 68) or the interaction with effector molecules (at positions 72 and 75). Our data confirmed the main manifestations as neurodevelopmental disorder with intellectual disability (85%), muscular hypotonia (83%), structural brain anomalies (77%), and visual impairment (70%). Combined analysis indicates a genotype-phenotype correlation; variants impacting the nucleotide binding cause a severe phenotype with intellectual disability, and variants outside the binding pocket lead to a milder phenotype with epilepsy. CONCLUSIONS: We confirm that disease-associated missense variants in RAB11B cause a neurodevelopmental disorder and suggest a genotype-phenotype correlation based on the impact on nucleotide binding functionality of RAB11B.

A promoter variant in the OTC gene associated with late and variable age of onset hyperammonemia.

Ornithine transcarbamylase deficiency (OTCD) is an X-linked inborn error caused by loss of function variants in the OTC gene typically associated with severe neonatal hyperammonemia. Rare examples of late-onset OTCD have also been described. Here, we describe an OTC promoter variant, c.-106C>A, in a conserved HNF4a binding site, identified in two male siblings in Family 1 whose first and only recognized episodes of severe hyperammonemia occurred at ages 14 and 39 years, respectively. We identified the same OTC variant segregating in a large family with late-onset OTCD with variable expressivity (Family 2). We show that this OTC promoter variant reduces expression >5-fold in a dual-luciferase assay that tests promoter function. Addition of an upstream OTC enhancer increases expression of both the wild type and the c.-106C>A variant promoter constructs >5-fold with the mutant promoter still about fourfold lower than the wild type. Thus, in both contexts, the promoter variant results in substantially lower OTC expression. Under normal demand on urea cycle function, OTC expression in hemizygous males, although reduced, is sufficient to meet the demand for waste nitrogen excretion. However, in response to severe metabolic stress with attendant increased requirements on urea cycle function, the impaired promoter function results in inadequate OTC expression with resultant hyperammonemia. In the absence of precipitating events, hemizygotes with this allele are asymptomatic, explaining the late age of onset of hyperammonemia in affected individuals and the incomplete penetrance observed in some individuals in Family 2.