Metachromatic leukodystrophy (MLD)

MLD is grouped by the age when symptoms start. The late-infantile form usually begins in the second year of life. MedlinePlus Genetics says it affects about 50 to 60 in 100 people with MLD. Juvenile forms begin later in childhood and affect about 20 to 30 in 100. Experts often split them into early-juvenile and late-juvenile MLD. The adult form begins in the teens or later and affects about 15 to 20 in 100. The form matters because the treatment options differ.

It depends on the form and on whether treatment happens early. Without treatment, late-infantile MLD moves fast. A 2025 expert review says children lose all major movement skills, such as sitting, standing and walking, before 40 months of age (a little over 3 years). They usually die within 5 years after symptoms begin, though good supportive care can lengthen survival. Later forms move more slowly, and survival varies. The same review says people with juvenile onset often do not reach age 20, and life expectancy in the adult form ranges from several years to decades. No number can predict one person's course.

MLD is rare. The U.S. Food and Drug Administration (FDA) estimates that it affects about 1 in 40,000 people in the United States. MedlinePlus Genetics gives a range of 1 in 40,000 to 1 in 160,000 people worldwide. It is much more common in a few communities where people share ancestry, such as part of the Navajo Nation and some groups in Israel.

No. When it approved a gene therapy in 2024, the FDA said there is no cure for MLD. But some treatments can change its course if they are given early enough. A one-time gene therapy made from a child's own stem cells is called Lenmeldy in the U.S. It is approved for children with late-infantile or early-juvenile MLD before symptoms, and for early-juvenile MLD with early symptoms. For late-juvenile and adult MLD with no or early symptoms, a donor stem cell transplant is considered the standard treatment. Both work best before symptoms begin.

Sometimes, depending on the form and the timing. European transplant recommendations say a donor transplant does not work in the earliest-onset MLD. They say it can help in juvenile or adult forms when done early in the disease. A 2025 review adds that about 10 to 15 in 100 people with MLD who have a transplant die, and more in some groups. For children with early-onset MLD found before symptoms, U.S. expert guidelines point to gene therapy with the child's own cells where it is available.

In the U.S., MLD was added to the Recommended Uniform Screening Panel, the federal list of conditions recommended for newborn screening, in a notice published December 22, 2025. Each state decides which conditions its program screens for, so not every baby is screened yet. Screening tests a baby's blood spot for sulfatides and enzyme activity, followed by genetic testing. It can find children before symptoms, when treatment works best.