Although more than 85% of children with DCD are affected by handwriting disorders, their characteristics and underlying mechanisms remain poorly known.

We aim to better identify the nature of handwriting disorders in subtyping DCD children.

School children aged between 5 to 15 years and exhibited a DCD (according to DSM-5) are eligible for inclusion. They were classified in three subtypes of DCD: ideomotor (IM), visual-spatial and/or constructional (VSC), and mixed (MX). They were assessed with a standardized handwriting evaluation including quality and speed and a clinical observation of motor gestual developmental and temporal-spatial organization of handwriting highlighting six qualitative criteria: irregular handwriting (criterion 1), immaturity of handwriting gesture (criterion 2), excessive pressure of the pen on the paper (criterion 3), neuro-vegetative responses (criterion 4), trembling (criterion 5), slow handwriting velocity (criterion 6). Two groups are established: children with poor handwriting (PH) and children with dysgraphia (DysG).

While 89% of children have handwriting disorders, only 20% exhibit dysgraphia. IM DCD is characterized by an immaturity of handwriting gesture and is associated with PH. Dysgraphia appears only in VSC and MX DCD which are characterized by the association of criteria 1, 2, 3, and 4. This association appears to more than 80% in DysG. Slow handwriting velocity is constant between PH and DysG.

Immaturity of handwriting gesture is a possible underlying mechanism of poor handwriting. Dysgraphia is associated with specific impairments in spatial organization of letters and in motor control of handwriting gesture.