TANGO2 deficiency disorder is a rare genetic disease caused by biallelic defects in TANGO2 gene.

We report the clinical phenotype of two children with TANGO2 deficiency disorder.

Patient 1 is a female child presenting with developmental delay and microcephaly during the second year of life, who evolved with severe cognitive impairment, facial dysmorphisms, spastic paraparesis, and atonic seizures. At age 13 years, she was hospitalized due to an episode of rhabdomyolysis complicated with cardiac arrhythmia and hypothyroidism. Patient 2 is a female child with dysmorphic facial features, cleft palate, and developmental delay who was diagnosed with DiGeorge syndrome. At age three years, she presented with an acute episode of severe rhabdomyolysis in the context of human herpesvirus 6 infection. After the resolution of this acute episode, she maintained recurrent muscle weakness with axial hypotonia and progressive spasticity of the lower extremities. In both patients, diagnosis of TANGO2 deficiency disorder was only confirmed after an acute metabolic crisis.

A high index of suspicion for TANGO2 deficiency disorder is needed in patients with developmental delay or other neurological symptoms and episodic rhabdomyolysis.