Antibodies to MOG (MOG-Abs) have been detected in 30–50% [2, 4] of children at first presentation of acquired demyelinating syndrome (ADS) [5], with two studies from the UK/France [4] and the Netherlands [6] suggesting that MOG-Abs identified at onset are associated with a non-MS disease course. The gene discussed is MOG; the disease is myeloid sarcoma.