Widespread and debilitating hemangiomas in a patient with enchondromatosis and D-2-hydroxyglutaric aciduria

An intermediate phenotype in IDH related enchondromatosis spectrum

Mosaic variants of IDH1 (isocitrate dehydrogenase-1) R132 and IDH2 (isocitrate dehydrogenase-2) R172 loci were detected in most of the bone cysts of Ollier and Maffucci series and in the blood and tissue samples of metaphyseal enchondromatosis with D-2-hydroxyglutaric aciduria (MC-HGA) patients. We aimed to report an intermediate phenotype comparing with the reported cases. The proband was a 9-year-old boy with widespread metaphyseal enchondromatosis involving metaphyses of long tubular bones, iliac bones and tubular bones of both hands and feet and sparing spine and flat and short bones. He underwent quad whole exome sequencing (index-both parents-healthy sibling). Sanger sequencing was performed for confirmation and segregation purposes. Heterozygous IDH1 R132H (c.395G > A) variant was detected in his blood via whole exome sequencing and Sanger analysis in mosaic state, 22% of the reads and Sanger signal. He had no D-2-hydroxyglutaric aciduria in urinary organic acid analysis. Our case is unique with the presence of IDH1 R132H variant in blood with metaphyseal enchondromatosis without D-2-hydroxyglutaric aciduria. It was a transitional phenotype. With his phenotype, we expand the IDH1/IDH2 related enchondromatosis phenotypes.

Neuronal Death, Glial Reactivity, Microglia Activation, Oxidative Stress and Bioenergetics Impairment Caused by Intracerebroventricular Administration of D-2-hydroxyglutaric Acid to Neonatal Rats

D-2-hydroxyglutaric acid (D-2-HG) accumulates and is the biochemical hallmark of D-2-hydroxyglutaric acidurias (D-2-HGA) types I and II, which comprehend two inherited neurometabolic diseases with severe cerebral abnormalities. Since the pathogenesis of these diseases is poorly established, we tested whether D-2-HG could be neurotoxic to neonatal rats. D-2-HG intracerebroventricular administration caused marked vacuolation in cerebral cortex and striatum. In addition, glial fibrillary acidic protein (GFAP), S-100 calcium binding protein B (S100B) and ionized calcium-binding adapter molecule 1 (Iba-1) staining was increased in both brain structures, suggesting glial reactivity and microglial activation. D-2-HG also provoked a reduction of NeuN-positive cells in cerebral cortex, signaling neuronal death. Considering that disturbances in redox homeostasis and energy metabolism may be involved in neuronal damage and glial reactivity, we assessed whether D-2-HG could induce oxidative stress and bioenergetics impairment. D-2-HG treatment significantly augmented reactive oxygen and nitrogen species generation, provoked lipid peroxidation and protein oxidative damage, diminished glutathione concentrations and augmented superoxide dismutase and catalase activities in cerebral cortex. Increased reactive oxygen species generation, lipoperoxidation and protein oxidation were also found in striatum. Furthermore, the antagonist of NMDA glutamate receptor MK-801 and the antioxidant melatonin were able to prevent most of D-2-HG-induced pro-oxidant effects, implying the participation of these receptors in D-2-HG-elicited oxidative damage. Our results also demonstrated that D-2-HG markedly reduced the respiratory chain complex IV and creatine kinase activities. It is presumed that these deleterious pathomechanisms caused by D-2-HGA may be involved in the brain abnormalities characteristic of early-infantile onset D-2-HGA.

IDH1 mutated acute myeloid leukemia in a child with metaphyseal chondromatosis with D-2-hydroxyglutaric aciduria

D-2-hydroxyglutaric aciduria (D-2-HGA) is a rare metabolic disorder characterized by developmental delay, hypotonia, and bi-allelic mutations in D-2-hydroxyglutarate dehydrogenase (D2HGDH) or a single gain-of-function mutation in isocitrate dehydrogenase 2 (IDH2). Metaphyseal chondromatosis with D-2-hydroxyglutaric aciduria (MC-HGA) is a type of D-2-HGA that has been previously reported in ten patients (OMIM 614875), three of whom had somatic mosaicism for R132 variants in isocitrate dehydrogenase 1 (IDH1). We describe a 3-year-old boy with MC-HGA who subsequently developed acute myeloid leukemia (AML) and was found to have an IDH1 R132C mutation in a leukemic bone marrow sample. Further testing revealed presence of somatic mosaicism for IDH1 R132C variant, suggesting an association of IDH1 in inducing myeloid leukemogenesis.

D-2-Hydroxyglutaric Aciduria with Enchondromatosis and Angiokeratoma Circumscriptum

In this study, we report a four-year-old male with D-2-hydroxyglutaric aciduria (D2HA) and enchondromatosis with a prior history of hyperpigmented, segmental whorls and streaks on his abdomen who later presented with an eruption of angiokeratoma circumscriptum within a similar distribution. His condition can likely be explained by underlying somatic mosaicism; however, a unifying culprit gene mutation has not yet been identified. To date, only 10 reported cases of D2HA with enchondromatosis are available in the literature with three reported skin findings. This is the first reported case of angiokeratoma circumscriptum associated with the rare condition of D2HA and enchondromatosis.