The diagnostic conundrum of late-onset developmental regression in child psychiatry: case series.

Background: Developmental regression in children, in the absence of neurological damage or trauma, presents a significant diagnostic challenge. The complexity is further compounded when it is associated with psychotic symptoms.

Method: We discuss a case series of ten children aged 6-10 years, with neurotypical development, presenting with late-onset developmental regression (>6 years of age), their clinical course and outcome at 1 year. A comprehensive clinical evaluation, laboratory investigations and neuroimaging ruled out any identifiable neurological cause.

Results: Mean age at regression was 7.65 (s.d. 1.5) years and mean illness duration was 10.1 (s.d. 8.5) months. The symptom domains included regression (in more than two domains - cognitive, socio-emotional, language, bowel and bladder incontinence), emotional disturbances, and hallucinatory and repetitive behaviours. Response to treatment was gradual over 6 months to 1 year. At 1-year follow-up, nine children did not attain pre-regression functioning, and residual symptoms included not attaining age-appropriate speech and language, socio-emotional reciprocity and cognitive abilities.

Conclusions: These cases demonstrate a unique pattern of regression with psychiatric manifestations, distinct from autism spectrum disorder and childhood-onset schizophrenia. The diagnostic dilemma arises from the overlap of symptoms with childhood disintegrative disorder (CDD), childhood-onset schizophrenia and autism. This study underscores the diagnostic intricacies of this clinical presentation and highlights the need for longitudinal follow-up to unravel the transitions in phenomenology, course and outcome. For severe manifestations such as developmental regression, where the illness is still evolving, considering CDD as a non-aetiological and transitory/tentative diagnosis would aid against premature diagnostic categorisation and provide scope for ongoing aetiological search.