An Unusual Cause for a Bilateral Ptosis Abstract. Immune-checkpoint-inhibitors are increasingly used in various malignancies. Autoimmune side effects such as colitis, hepatitis or skin reactions are well known, on the other hand neurological autoimmune complications such as myasthenic syndromes, myopathies or overlap syndromes with potentially life-threatening complications are less common and not well understood. A precise diagnosis has far reaching therapeutic consequences. Here we present the case of a patient under immune checkpoint inhibitor therapy, in which the diagnosis, due to the presence of overlap symptoms, is shown to be challenging. However, it was crucial to find the correct diagnosis in order to choose the proper therapy.