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Evaluations Of Exercise Intolerance With Cardiopulmonary Exercise Tests In A 24-Year-Old Young Male With Obesity With Tetrahydrobiopterin Deficiency: A Case Report, Chun-Yu Chen, Shin-Tsu Chang, Ko-Long Lin, Mu-Hsun Wu

Rehabilitation Practice and Science

Phenylketonuria (PKU) is a rare amino acid metabolism genetic disorder. Tetrahydrobiopterin (BH4) metabolism defects cause variant PKU. BH4 coenzyme deficiency disables phenylalanine metabolism into tyrosine, causing brain damage and intellectual impairment. Patients follow a low-phenylalanine diet for life, increasing the risk of obesity, hypertension, and metabolic syndrome. A 24-year-old male patient with BH4 deficiency underwent a pulmonary function test and cardiopulmonary exercise test (CPET). Forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were within normal values, with an 80.68% ratio. The 20-watt bicycle exercise test indicated moderate functional impairment (27.3 ml/kg/min of peak oxygen intake). The …