Certain inborn errors of metabolism have been suggested to increase the risk of autistic behavior. In an animal model, propionic acid ingestion triggered abnormal behavior resembling autism. So far only a few cases were reported with propionic acidemia and autistic features. From a series of twelve consecutively diagnosed cases with propionic acidemia, we report on eight patients with autistic features. The patients were followed 2-4 times a year and underwent regular clinical, dietary and laboratory investigations. Psychological evaluation was performed every second to fourth year. All patients were compliant with the standard diet and carnitine supplementation. None of the patients had frequent metabolic decompensations. From the metabolic factors known to impact neuropsychological outcome we detected chronically decreased valine levels and altered valine to leucine ratios in five out of the eight patients. Recurrent lactic acid elevations were present in six out of the eight patients. Five of the eight patients were diagnosed with Autism Spectrum Disorder, four of them had pathogenic variants in PCCB. Disorder according to DSM-IV and/or DSM-5 criteria. One of the patients diagnosed with propionic acidemia by newborn screening had the most significant behavioral features and another was diagnosed with Autism Spectrum Disorder prior to propionic acidemia. We hypothesize that chronic suboptimal intracellular metabolic balance may be responsible for the increased risk for autistic features in propionic acidemia. We propose that patients diagnosed with propionic acidemia should be screened for Autism Spectrum Disorder.

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Background Neuromuscular disorders (NMD) are intrusive medical conditions with implications for psychosocial development. Objectives This paper explores illness perceptions and illness identity dimensions of youth with NMD. First, we compare illness identity outcomes and illness perceptions of NMD patients with a comparison group of adolescents with type 1 diabetes mellitus (DM). Second, we report about the relationships between NMD-related variables and illness perceptions and illness identity. Methods Scores on the Brief Illness Perception Questionnaire and the Illness Identity Questionnaire were compared between a group of NMD patients ( N = 59; 12–22 years) and an age- and gender-matched group of DM patients ( N = 118). NMD-related variables included time since diagnosis, prognosis, wheelchair use, and physical limitations. Results Youth with NMD scored significantly higher on two of the four illness identity dimensions than youth with DM. NMD patients reported significantly less positive illness perceptions, experienced more physical symptoms, and had a lower score on understanding of their illness. Within the NMD group, wheelchair-users have a better understanding of their disease than those who are not wheelchair-bound. Conclusions The present study is the first to investigate illness identity and illness perceptions in NMD. More research is needed to provide insight in the identity formation process of the growing group of adolescents with NMDs.

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