De novo ARF3 variants cause neurodevelopmental disorder with brain abnormality.

An optimal Golgi transport system is important for mammalian cells. The adenosine diphosphate (ADP) ribosylation factors (ARF) are key proteins for regulating cargo sorting at the Golgi network. In this family, ARF3 mainly works at the trans-Golgi network (TGN), and no ARF3-related phenotypes have yet been described in humans. We here report the clinical and genetic evaluations of two unrelated children with de novo pathogenic variants in the ARF3 gene: c.200A > T (p.Asp67Val) and c.296G > T (p.Arg99Leu). Although the affected individuals presented commonly with developmental delay, epilepsy and brain abnormalities, there were differences in severity, clinical course and brain lesions. In vitro subcellular localization assays revealed that the p.Arg99Leu mutant localized to Golgi apparatus, similar to the wild-type, whereas the p.Asp67Val mutant tended to show a disperse cytosolic pattern together with abnormally dispersed Golgi localization, similar to that observed in a known dominant negative variant (p.Thr31Asn). Pull-down assays revealed that the p.Asp67Val had a loss-of-function effect and the p.Arg99Leu variant had increased binding of the adaptor protein, Golgi-localized, γ-adaptin ear-containing, ARF-binding protein 1 (GGA1), supporting the gain of function. Furthermore, in vivo studies revealed that p.Asp67Val transfection led to lethality in flies. In contrast, flies expressing p.Arg99Leu had abnormal rough eye, as observed in the gain-of-function variant p.Gln71Leu. These data indicate that two ARF3 variants, the possibly loss-of-function p.Asp67Val and the gain-of-function p.Arg99Leu, both impair the Golgi transport system. Therefore, it may not be unreasonable that they showed different clinical features like diffuse brain atrophy (p.Asp67Val) and cerebellar hypoplasia (p.Arg99Leu).

[Intravenous cyclophosphamide pulse therapy for refractory juvenile dermatomyositis].

We described three children with juvenile dermatomyositis (JDM) refractory to the conventional therapy. They were successfully treated with intravenous cyclophosphamide (IVCY) pulses, and two of them were administered plasma exchange (PE) before IVCY. Case 1. A 17-year-old girl with JDM was previously treated for 2 years with the combination of prednisolone, intravenous gamma-globulin, methotrexate, and azathioprine. However, muscle weakness gradually progressed. She failed to hold her sitting position and to rise her arms, but both serum CK and aldolase were stable. After the episode of aspiration pneumonia the follow-up muscle biopsy was performed, which revealed muscle degeneration and massive mononuclear cell infiltration in perivascular area. The erythrocyte sedimentation rate (ESR) and fibrin degradation product E (FDP-E) levels were gradually increased. Because the active inflammation of muscle and muscle vasculature was suspected, the PE and IVCY combination therapy was administered. During the 6 courses of the therapy, muscle weakness was markedly improved so that she could hold herself at the sitting position and could have meals by herself. Case 2. A 5-year-old boy with JDM was treated for 8 months with prednisolone p.o., but his muscle strength became worse. The muscle enzyme levels, such as serum CK and aldolase, were not reflecting his status of the disease, but FDP-E levels were increased. Muscle MRI and biopsy revealed the inflammatory changes of perivascular area of muscle. The PE and IVCY combination therapy was effective, and he became able to walk and run by himself. Case 3. A 14-year-old boy was diagnosed as having JDM when he was 10 years of age, and treated with prednisolone p.o., and subsequently with intravenous methylprednisolone pulses and azathioprine. Three years later the flares were observed accompanied with the elevations of serum CK and FDP-E. The administration of IVCY improved muscle strength as well as serum muscle enzyme and FDP-E levels. These findings indicated that the clinical manifestations of JDM should be closely monitored, that the serum levels of muscle enzymes including CK and aldolase were sometimes not indicative for the flares of JDM, and that muscle MRI and re-biopsy examination were needed for the children with progressive muscle weakness. In addition, determination of ESR and FDP-E was not specific but helpful to detect flares of the disease in some cases.