Key result
CPET in tetrahydrobiopterin deficiency reveals moderate functional impairment driven by obesity with a 27.3 peak VO2.
Why the study?
Patients with tetrahydrobiopterin deficiency variant PKU are at increased risk of obesity and metabolic complications, but evaluations of exercise intolerance in this population are limited.
Does cardiopulmonary exercise testing evaluate cardiorespiratory fitness in a patient with tetrahydrobiopterin deficiency and obesity?
Case Report (n=1)
No
Does cardiopulmonary exercise testing evaluate cardiorespiratory fitness in a patient with tetrahydrobiopterin deficiency and obesity?
CPET identified moderate functional impairment caused by obesity in a patient with BH4 deficiency, highlighting its utility in guiding weight control and exercise programs.
Answers are grounded in this paper and cite their sources.
Single case in BH4-deficient PKU cautions against routine extrapolation; leaves open need for prospective data on diet-related cardiopulmonary risks.
Background: 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. Case Presentation: 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 test achieved 81% and 70% of the target and reserve heart rates, respectively. The patient’s body mass index was 29.9 kg/m2, causing a high resting metabolic rate and oxygen uptake. The need for oxygen uptake is more prominent during high-intensity exercise, thus his functional impairment was caused by obesity. Conclusion: CPET evaluates cardiorespiratory fitness in patients with PKU, providing appropriate aerobic and resistance training to improve prognosis with a weight control program.
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Chen et al. (2023) conducted a case report in Tetrahydrobiopterin deficiency (variant phenylketonuria) and obesity (n=1). Cardiopulmonary exercise test (CPET) was evaluated on Peak oxygen uptake (VO2). Cardiopulmonary exercise testing in a 24-year-old male with tetrahydrobiopterin deficiency revealed a peak oxygen uptake of 27.3 ml/kg/min, indicating moderate functional impairment primarily caused by obesity.
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