We reported a patient carrying two large de novo interstitial duplications including a 20 Mb duplication at 1q42-q44 and a 14.2 Mb duplication at 9q21.12-q21.33. This type of case is quite rare.

We summarized the clinical characteristics of patients with distal 1q trisomy and patients with 9q21 duplication respectively.

We compared the phenotypes of distal 1q trisomy and 9q21 duplication.

We concluded that the distal 1q trisomy may have contributed to the features of macrocephaly, prominent forehead and limb abnormalities of our patient.

Either the distal 1q trisomy or the 9q21 duplication or both could have contributed to our patient’s clinical presentation of growth retardation, developmental delay and dysmorphic features including hypertelorism, low-set ears and abnormal nose/nasal bridge.