Second Department of Neurology, National and Kapodistrian University of Athens, School of Medicine.
Iatropolis Magnetic Resonance Diagnostic Centre.
Neurologist. 2020 Dec 30;26(1):20-21. doi: 10.1097/NRL.0000000000000295.
Phenylketonuria (PKU) is the most common inborn error of amino acid metabolism and causes neurological manifestations because of excessive accumulation of phenylalanine (PHE). It can also affect adult patients who discontinue their treatment, even if they had been under adequate metabolic control during childhood. For that reason, it is recommended that PKU treatment should be continued throughout life and target PHE levels for adult patients should range between 120 and 600 μmol/L.
The authors present an adult patient with PKU who discontinued treatment and developed cognitive dysfunction because of high blood levels of PHE. Brain magnetic resonance imaging (MRI) of the patient was characteristic for PKU, presenting periventricular and callosal white matter hyperintensities in T2 and fluid-attenuated inversion recovery sequences, which were additionally associated with true restriction in diffusion-weighted imaging sequence, a far less recognized PKU neuroimaging feature.
Cognitive dysfunction and psychiatric disorders can be present in adult patients with PKU who discontinue treatment and have poor PHE metabolic control. The presence of white matter hyperintensities in T2 and fluid-attenuated inversion recovery MRI-sequences is a well-described neuroimaging feature of PKU, but diffusion-weighted imaging sequence may also be reliable in detecting brain lesions in patients with PKU. PKU lesions should be considered in the differential diagnosis of true diffusion restriction in brain MRI of patients with PKU history or those who might have escaped newborn screening diagnosis but present neurocognitive dysfunction. Appropriate treatment for the management of PKU should be initiated for the reversal of the clinical and neuroimaging findings.
苯丙酮尿症（PKU）是最常见的氨基酸代谢遗传疾病，由于苯丙氨酸（PHE）的过度积累，会导致神经系统表现。它也会影响成年患者，即使他们在儿童时期已经得到了充分的代谢控制，也会停止治疗。因此，建议 PKU 的治疗应持续终生，成年患者的 PHE 水平应在 120 至 600μmol/L 之间。
作者介绍了一名成年 PKU 患者，因血液 PHE 水平升高而停止治疗，并出现认知功能障碍。该患者的脑部磁共振成像（MRI）具有 PKU 的特征，在 T2 和液体衰减反转恢复序列中出现脑室周围和胼胝体白质高信号，此外在弥散加权成像序列中还存在真正的受限，这是一种远不如 PKU 神经影像学特征广泛认知的特征。
停止治疗且 PHE 代谢控制不佳的成年 PKU 患者可能会出现认知功能障碍和精神障碍。T2 和液体衰减反转恢复 MRI 序列中的白质高信号是 PKU 的一种明确的神经影像学特征，但弥散加权成像序列也可能在检测 PKU 患者的脑部病变方面具有可靠性。对于有 PKU 病史或可能逃避新生儿筛查诊断但出现神经认知功能障碍的患者，应考虑将 PKU 病变作为脑 MRI 中真正弥散受限的鉴别诊断。对于 PKU 的管理，应启动适当的治疗以逆转临床和神经影像学发现。
