Historically, some of the most severe presentations of developmental regression were recognised under the diagnosis of Childhood Disintegrative Disorder (CDD/Heller’s syndrome), a condition characterised by catastrophic global regression following a period of apparently typical development. CDD was first identified in 1908 by Theodor Heller, an Austrian educator who lived from 1869 to 1938. His description came more than three decades before autism was characterised by Leo Kanner and Hans Asperger.

CDD was absorbed into the autism spectrum diagnosis at the same time as Asperger's—in the DSM-5 in 2013, and in the ICD-11 when it took effect in 2022. But for a condition already this rare, the name was one of the few things holding its recognition together. Once it was gone, the awareness, research, and support built around it largely disappeared with it. However, with the removal of CDD as a distinct diagnosis and its absorption into broader autism spectrum classifications, many families feel these children and their unique clinical trajectories have become increasingly difficult to identify, study, and research as distinct subgroups. 

Beyond Disintegration believes we cannot afford to lose sight of the unique experiences and needs of these children.

Our work includes children whose regression occurred both before and after the historic CDD age threshold. Whilst earlier regression can be more difficult to define objectively, many families describe clear developmental loss in children who were previously thriving, progressing, learning, communicating, and engaging before experiencing dramatic and life-altering decline. 

Many children within this subgroup ultimately receive broad neurodevelopmental diagnoses, most commonly autism spectrum disorder (ASD), often alongside ADHD-like traits and other behavioural or sensory features that emerge during or following regression. 

This creates a major scientific and diagnostic challenge. By the time many children are first assessed, the regression has often already occurred, and the child may now present with autistic traits, hyperactivity, sensory dysregulation, repetitive behaviours, communication difficulties, attentional problems, or agitation. Because these children were often developing typically beforehand, clinicians are frequently relying on retrospective developmental history, parental reporting, educational observations, and home videos to understand what changed.

The research that might answer these questions remains scarce. Only a handful of groups in the US and UK study CDD at all, and researchers describe how difficult funding has become since the condition was merged into the autism spectrum and was no longer treated as a distinct diagnosis. Where the work has been done, the findings are striking: one group at Yale, working with one of the largest CDD cohorts assembled anywhere and the first neurogenetic study of the condition, reported differences between CDD and other forms of autism at every level they examined. The researchers themselves remain careful about what this means—whether CDD is a distinct and particularly devastating subtype of autism, or a separate condition that shares some of its features, they say openly that we do not yet know enough to be certain. What they agree on is that CDD warrants study in its own right, and that far more of it is needed.

Beyond Disintegration believes the presence of ASD-like features following regression does not necessarily answer the deeper mechanistic question of what may have contributed to the regression itself. 

These children were once speaking, learning, connecting, and functioning typically or near typically. 

Then something changed.