AbstractParents of children with severe inborn errors of metabolism frequently face stressful events related to the disease of their child and are consequently at high risk for developing parental posttraumatic stress disorder (PTSD). Assessment and subsequent treatment of PTSD in these parents is however not common in clinical practice. PTSD can be effectively treated by Eye Movement Desensitization and Reprocessing (EMDR), however no studies have been conducted yet regarding the effect of EMDR for parental PTSD. EMDR is generally offered in multiple weekly sessions which may preclude participation of parents as they are generally overburdened by the ongoing and often intensive care for their child. Therefore, we offered time-limited EMDR with a maximum of four sessions over two subsequent days to two parents of mucopolysaccharidosis type III (MPS III) patients to explore its potential effects. Both qualitative and quantitative outcomes were used to evaluate treatment effects. Both parents felt more resilient and competent to face future difficulties related to the disease of their child, and no adverse effects were reported. Quantitative outcomes showed a clinically significant decrease in post traumatic stress symptoms and comorbid psychological distress from pre- to post treatment, and these beneficial effects were maintained at follow-up. In conclusion, time-limited EMDR may be a highly relevant treatment for traumatized parents of children with MPS III, and probably also for parents of children with other rare progressive disorders. Further research is needed to validate the efficacy of EMDR in this specific population.