When evaluating children with global developmental delay without evident etiological factors, extensive investigations are required, preferably following a clinical suspicion algorithm. In the last years the development of genetics identified many rare syndromes and has become a very important diagnostic tool in unexplained cases investigation.Objective: We report the case of a girl followed since the age of 9 months for global developmental delay (GDD) and the complex journey to her diagnostic, comparing the results with the existing literature data.Case presentation: The girl, aged 30months, had no perinatal history, but the development was slow, with important hypotonia, no sitting or walking, severe discontact and midline strereotypia, oculogyric episodes. She also presents some dysmorphism and a striking abnormal hair (thin, dry, frizzy), which imposed differential diagnosis with conditions with particular hair.

Results: She was investigated - metabolic, EEG, ophtamological, nerve conduction studies, electronic microscopy for the hair, all with normal results. Brain MRI showed a thin corpus callosum. At  2 years genetic whole exome sequencing was performed, revealing a mutation in AHDC1 gene, but also a mutation in PADI3 gene, explaining in the context of the diagnosis of Xia-Gibbs syndrome the association of the particular hair - uncombable hair syndrome.Conclusions: Xia-Gibbs syndrome is a newly described disordered, the main features being GDD, hypotonia, severe language impairment, autistic traits, sleep apnea and epilepsy. Genetic testing should be placed up in the investigation plan of children with developmental delay, in order to allow establishing an early follow-up and prevent reported complications.