Children and adults with KMT2B mutations usually presents in childhood as follows:
- Development of dystonia (a medical term for muscle spasms), which usually starts in the legs, but can affect the whole body including all four limbs, neck, face and voice. Patients may experience difficulties in walking, running, writing, sitting, eating and speaking.
- Some patients have learning difficulties and delayed development.
- Some patients also have other features, such as learning difficulties, a small head size, reduced height, eye abnormalities and behavioural issues.