White matter hypomyelination

Protein hypomyelination is a common form of protein disease. For example, if this happens when the fetus is in the third to sixth month in the womb, it will often lead to developmental abnormalities in the child, viral infections, poisoning, and some autoimmune diseases. It will also have a relatively adverse effect on the child's nervous system development.

Causes of hypomyelination of white matter

If children are affected by certain secondary factors such as viral infection, suffocation, poisoning, autoimmune disease, etc., or certain primary factors such as multiple sclerosis, Schilder's disease, etc., they will develop demyelinating lesions. Demyelination has a significant impact on the development of the child's nervous system, often leading to disabilities such as mental retardation, epilepsy, language disorders, and limited mobility. MRI is helpful for diagnosis.

Differential diagnosis:

(A) Metachromatic leukodystrophy , also known as sulfatidosis, is an autosomal recessive disease that is caused by arylsulfatase A deficiency and leads to poor myelination. It is caused by mutations in the MLD gene encoding lysosomal arylsulfatase A (ASA). MLD is located at 22q13.33 and has many types of mutations. It can be roughly divided into two groups: patients with type I mutations cannot produce active ASA, and no ASA activity can be detected in their cultured cells; patients with type A mutations can synthesize a small amount of active ASA. The patient's phenotype depends on the type of gene mutation: homozygous type I mutations or those with two different type I mutations show clinically the late infantile type; those with one type I and one type A mutation show the adolescent or juvenile type; and when both mutations are type A, the disease presents as the adult type. A small number of patients with this disease, especially those with the adolescent type, do not develop the disease due to MLD mutations and their ASA activity is normal. This is because the patients lack a lysosomal protein, sulfatide activating factor (SAP1). Such patients are also known as activator-deficient metachromatic leukodystrophy.

2. Adrenoleukodystrophy

There are two types of adrenoleukodystrophy that are inherited. One is the more common X-linked inheritance (X-linked adrenoleukodystrophy, XLALD or ALD for short); the other is autosomal recessive inheritance, which occurs in newborns and is called neonatal adrenoleukodystrophy (NALD). The diagnosis of adrenoleukodystrophy relies on the following examinations: ① CT and MRI; ② electrophysiological examination. The early evoked potentials and nerve conduction velocities of children with ALD are normal. In adult AMN, the nerve conduction velocity slows down and the brainstem auditory evoked potential is abnormal; ③ Cerebrospinal fluid and ALD are mostly normal, but there may be a slight increase in protein and cell count. NALD often shows increased cerebrospinal fluid protein; ④ increased VLCFA in plasma and skin fibroblasts, especially C26 fatty acid, and increased C26/C22 ratio, which are of diagnostic significance; ⑤ in the event of Addison's crisis with adrenal insufficiency, blood cortisol decreases. When no crisis occurs, ACTH stimulation test can also detect a decrease in adrenal compensatory reserve. For male Addison's disease, VLCFA should be tested even if no neurological symptoms are seen to avoid misdiagnosis.