This paper presents spazioD, a design case around the topic of dyslexia. Building on selected contributions from the literature on infrastructuring in participatory design and publics, it proposes that digital platforms are artefacts that can help infrastructuring the formation of publics and study their biography. The paper then unfolds describing the context in which the case was situated, presenting a specific digital platform (i.e. Facebook) and how it was enacted. The contribution of the paper is threefold: it provides a practice-based instance of the activities entangled in the infrastructuring of publics; building on this description, it shows how a digital platform can contribute to infrastructuring; and, finally, it articulates how the analytical tool embedded in the digital platform contribute to and influence the interpretation of an infrastructuring process and their limitations.