We are presenting a case of a 13 years old child who presented with normal development till 3 years of age followed by deterioration in previously acquired language and social skills with stereotypic hand movements suggestive of Childhood Disintegrative Disorder. This case is reported as this condition is very rare. Introduction Childhood disintegrative disorder, first described by Theodore Heller, is a condition in which young children develop normally until age 3 or 4, but then demonstrate a severe loss of social, communication and other skills. It’s also called Heller’s syndrome, dementia infantilis, disintegrative psychosis and pervasive disintegrative disorder.1 It affects 1 in 100,000 children and more boys are affected than girls.2