NEWBORN SCREENING FOR PILOT STUDY FOR ADRENOLEUKODYSTROPHY (ALD)

新生儿筛查的目标是发现新生儿中可能致命或致残的疾病，从而为早期治疗提供机会，通常是在儿童仍无症状时。这种早期发现和治疗可以对受影响儿童的临床严重程度产生深远影响。如果得不到诊断和治疗，目标疾病的后果可能是可怕的，许多会造成不可逆转的神经损伤，智力，发育和身体残疾，甚至死亡。2006年，美国医学遗传学学会（ACMG）制定了新生儿筛查指南，建议所有新生儿筛查31种“核心疾病”，并报告在核心评估期间确定的26种次要疾病。这些建议已被卫生与公众服务部（HHS）新生儿和儿童遗传性疾病咨询委员会（ACHDNC）（由2000年《儿童健康法》授权）和卫生与公众服务部秘书接受。大多数州现在使用这种或非常类似的面板进行新生儿筛查。目前，已经发现了数千种罕见疾病，数百种可能从新生儿筛查中受益。 X-连锁肾上腺脑白质营养不良（ALD）是一组称为脑白质营养不良的遗传性疾病之一，会导致髓鞘受损，髓鞘是大脑中包围神经细胞的绝缘膜。女性有两条X染色体，是疾病的携带者，但由于男性只有一条X染色体，缺乏额外X染色体的保护作用，因此他们受到的影响更严重。患有X-ALD的人在大脑和肾上腺皮质中积累高水平的饱和极长链脂肪酸（VLCFA）。髓鞘的丢失和肾上腺的进行性功能障碍是X-ALD的主要特征。虽然几乎所有的X-ALD患者都患有肾上腺功能不全，也称为阿狄森病，但神经系统症状可以开始于儿童或成年。儿童大脑型是最严重的，发病年龄在4至10岁之间。最常见的症状通常是行为变化，如异常退缩或攻击性，记忆力差，以及学校表现差。其他症状包括视力丧失、学习障碍、癫痫发作、发音不清、吞咽困难、耳聋、步态和协调障碍、疲劳、间歇性呕吐、皮肤色素沉着增加和进行性痴呆。较温和的成人发病形式也称为肾上腺脊髓神经病（AMN），通常在21岁至35岁之间发病。症状可能包括进行性僵硬、下肢无力或瘫痪以及共济失调。虽然成人发病的ALD比经典的儿童形式进展得更慢，但它也可能导致大脑功能的恶化。几乎一半的X-ALS携带者将发展为较温和的X-ALD形式。 肾上腺功能必须定期检查所有ALD患者。肾上腺激素治疗可以挽救生命。ALD的症状和支持治疗包括物理治疗，心理支持和特殊教育。儿童脑X-ALD患者的预后通常很差，因为进行性神经功能恶化，除非早期进行骨髓移植。死亡通常发生在症状出现后1至10年内。成人AMN将在数十年内进展。

The goal of newborn screening is to detect potentially fatal or disabling conditions in newborns, thereby providing a window of opportunity for early treatment, often while the child is still asymptomatic. Such early detection and treatment can have a profound impact on the clinical severity of the condition in the affected child. If left undiagnosed and untreated, the consequences of the targeted disorders can be dire, many causing irreversible neurological damage, intellectual, developmental and physical disabilities, and even death. In 2006, the American College of Medical Genetics (ACMG) developed newborn screening guidelines that recommend that all newborn infants be screened for 31 "core conditions" and that 26 secondary conditions identified during the core evaluations be reported. These recommendations have been accepted by the Department of Health and Human Services (HHS) Advisory Committee on Heritable Disorders in Newborns and Children (ACHDNC) (authorized by the Children's Health Act of 2000), and by the Secretary of HHS. Most states now use this or very similar panels for newborn screening. Currently, there are thousands of rare disorders that have been identified and hundreds that could potentially benefit from newborn screening. X-linked Adrenoleukodystrophy (ALD) is one of a group of genetic disorders called the leukodystrophies that cause damage to the myelin sheath, an insulating membrane that surrounds nerve cells in the brain. Women have two X chromosomes and are the carriers of the disease, but since men only have one X chromosome and lack the protective effect of the extra X chromosome, they are more severely affected. People with X-ALD accumulate high levels of saturated, very long chain fatty acids (VLCFA) in the brain and adrenal cortex. The loss of myelin and the progressive dysfunction of the adrenal gland are the primary characteristics of X-ALD. While nearly all patients with X-ALD suffer from adrenal insufficiency, also known as Addison's disease, the neurological symptoms can begin either in childhood or in adulthood. The childhood cerebral form is the most severe, with onset between ages 4 and 10. The most common symptoms are usually behavioral changes such as abnormal withdrawal or aggression, poor memory, and poor school performance. Other symptoms include visual loss, learning disabilities, seizures, poorly articulated speech, difficulty swallowing, deafness, disturbances of gait and coordination, fatigue, intermittent vomiting, increased skin pigmentation, and progressive dementia. The milder adult-onset form is also known as adrenomyeloneuropathy (AMN), which typically begins between ages 21 and 35. Symptoms may include progressive stiffness, weakness or paralysis of the lower limbs, and ataxia. Although adult-onset ALD progresses more slowly than the classic childhood form, it can also result in deterioration of brain function. Almost half the women who are carriers of X-ALS will develop a milder form of X-ALD. Adrenal function must be tested periodically in all patients with ALD. Treatment with adrenal hormones can be lifesaving. Symptomatic and supportive treatments for ALD include physical therapy, psychological support, and special education. Prognosis for patients with childhood cerebral X-ALD is generally poor due to progressive neurological deterioration unless bone marrow transplantation is performed early. Death usually occurs within 1 to 10 years after the onset of symptoms. Adult-onset AMN will progress over decades.