What is MMN? The disorder Euphoria’s Eric Dane’s ALS was mistaken for

Eric Dane was well-known for his roles in popular TV shows (Picture: Pief Weyman/NBC via Getty Images) When Grey’s Anatomy and Euphoria star Eric Dane passed away from ALS in February this year, the world was heartbroken. The neurological disorder, which is the most common form of Motor Neuron Disease (MND), accounting for 90% of all cases, was at the forefront of health news. But now, in his posthumous memoir My Book of Days: A Memoir in Moments, Eric revealed his terminal condition was mistaken for a treatable illness. After seeking treatment for struggling to use his right hand, the actor saw numerous specialists, before being misdiagnosed with Multifocal Motor Neuropathy (MMN). Much rarer than ALS, he described the condition as a ‘rare autoimmune disorder’, and the misdiagnosis was only evident when he didn’t respond to the treatment. So, here’s everything you need to know about MMN… Look beyond the headlines Get a curated list of the most important stories of the weekend every Sunday from our weekend editor Jess Austin. Look beyond the headlines with exclusive articles, emotive interviews and must-read explainers from our expert team of reporters across news, lifestyle and entertainment. Sign up here. What is Multifocal Motor Neuropathy? ‘Multifocal Motor Neuropathy is a rare neurological condition in which the body produces antibodies that block the conduction of electrical impulses along the motor nerves that supply the body’s muscles,’ consultant neurologist Mark Weatherall, tells Metro. ‘The consequence of this is that the muscles do not work properly, causing weakness without any loss of sensation.’ Eric playing Mark in Grey’s Anatomy before his ALS progressed (Picture: Randy Holmes/Disney General Entertainment Content via Getty Images) This usually comes on slowly, but the doctor adds it can be progressive over a number of weeks or months, or sometimes even longer. What are the symptoms? Ask Metro Use AI to go deeper into the stories you care about – powered by Metro and trusted publications. From the outside, it can look similar to ALS, but Asal Shirazi BEM, the founder and CEO of the Autoimmune Support and Awareness Foundation tells Metro which both impact movement rather than sensation. ‘It causes weakness that is often greater on one side than the other, typically beginning in a hand or forearm,’ she explains. ‘Someone might notice difficulty turning a key, fastening buttons, writing or holding objects. Other symptoms include muscle cramps, twitching, wrist drop or foot drop.’ Over time, those with the condition can see muscle wasting, although significant numbness or loss of sensation is unusual, which Asal says helps distinguish MMN from many other peripheral nerve conditions. Is it curable? While both experts say there is currently no cure for Multifocal Motor Neuropathy, that doesn’t mean it isn’t treatable. ‘It can be brought under control,’ Dr Weatherall, for The Medical Chambers Kensington, says. ‘The treatments aim to suppress the body’s production of the antibodies that block the nerve impulses.’ This can be done through infusions. ‘The main treatment is intravenous immunoglobulin, or IVIg,’ Asal explains. ‘This is a preparation of antibodies from donated plasma, given through a vein to modify the abnormal immune response.’ Although, she explains that responses to this can vary and established nerve damage can limit recovery. Why can it be mistaken for ALS? ‘MMN can look like motor neuron disease,’ Dr Weatherall says. ‘This is because both conditions cause weakness without impairing sensation. ‘The conditions can be distinguished by detailed electrical tests of the nerves and muscles that would typically be required to make a definitive diagnosis of ALS, and by a blood test that looks for the antibodies associated with the condition.’ Eric was misdiagnosed with a condition that can easily confused with ALS (Picture: Pief Weyman/NBC via Getty Images) MMN and ALS can both cause progressive weakness, muscle wasting and twitching, which is why confusion is possible. Asal explains: ‘This is the case for most autoimmune conditions where early diagnosis is delayed due to overlapping symptoms. ‘One important clue to MMN is “conduction block”, where electrical signals fail to travel properly along part of a motor nerve. MMN also typically lacks the upper motor neuron signs, such as spasticity and abnormal reflex patterns, that can occur in ALS. ‘That being said, conduction block is not detectable in every case, so diagnosis requires the whole clinical picture rather than one test result.’ Treatment times need to be quicker ‘The most important message is that progressive weakness deserves timely neurological assessment because some causes respond to treatment. A 2025 study across nine UK neuroscience centres found that more than half of the 95 people studied experienced a diagnostic delay exceeding one year after their first neurological assessment. Deals of the Day The Orlando holiday deal Disney fans shouldn't miss We're adding this discounted NEOM gift set straight to basket Want an LED face mask for less? This Black Friday deal could save you hundreds This teeth whitening sale could save you up to 64% before Black Friday QVC shoppers can save £159 on Elemis' biggest beauty gift set of the year For patients, recognising a treatable condition can make an enormous difference.’ Do you have a story you’d like to share? Get in touch by emailing MetroLifestyleTeam@metro.co.uk Arrow MORE: Why you always wake up between 2am and 4am — and what to do about it Arrow MORE: I couldn’t stop drinking – but I’m not an alcoholic Arrow MORE: The new night out trend that has people saying ‘we’re in hell’ The Sunday Edit Look beyond the headlines with exclusive articles, emotive interviews and must-read explainers from our expert team of reporters across news, lifestyle and entertainment.