TANGO2 deficiency disorder in a 61-year-old male with episodic weakness, rhabdomyolysis, myotonia, and a novel missense variant.

TANGO2 Deficiency Disorder (TDD) is an autosomal recessive condition, most commonly diagnosed in childhood. Clinical features may include episodic movement disorders, seizures, cognitive impairment, hypothyroidism, and metabolic crises marked by rhabdomyolysis and life-threatening cardiac symptoms. A small number of adults, thought to largely represent the milder end of the phenotypic spectrum, have received a diagnosis of TDD in their 30's or 40's, though no genotype-phenotype correlations have been established to date. In this case report, we present a 61-year-old man with mild intellectual disability and recurrent muscle weakness who was diagnosed with TDD during an inpatient hospitalization for diverticulitis, prostatitis, and muscle weakness, ultimately attributed to rhabdomyolysis. Genetic testing revealed a deletion of exons 3-9 in TANGO2 along with a novel missense variant (c.187G > T; p.Gly63Cys) on the other allele. The patient was started on vitamin B-complex with additional pantothenic acid (500 mg daily) and subsequently noted improvement in his speech and energy levels. To our knowledge, this case describes the oldest known individual living with TDD by two decades. Additionally, the patient's relatively mild symptom profile and previously unreported missense variant in TANGO2 may represent the first known example of genotype-phenotype correlation in TDD.