Understanding ASMD

What is ASMD?

An inherited disease with multiorgan symptoms that can worsen over time

ASMD (acid sphingomyelinase deficiency) is historically known as Niemann-Pick disease types A, A/B, and B. This disease can be passed down through families, and has a wide array of symptoms that can impact your life in multiple ways. ASMD often affects the liver, lungs, spleen, and blood, as well as the digestive system.

There are 3 types of ASMD, which vary in symptom severity and appearance

	TYPE A	TYPE A/B	TYPE B (most common*)
First appearance of symptoms	Early infancy	Infancy to childhood	Infancy to adulthood
Organs involved	Affects many key organs in the body, including the brain	Affects many key organs in the body, including the brain	Affects many key organs in the body, with little or no impact to the brain
Rate of symptom progression	Rapid	Varies in progression rate	Slow
Severity	Most severe	Varies in severity	Least severe

*Based on patient population from a multicenter, historical cohort study (N=100).

What causes ASMD?

ASMD is an inherited condition caused by genetic variants (changes in your genes). These changes can alter certain processes in your body and result in disease. The gene involved in ASMD is called SMPD1.

The role of SMPD1 is to make an enzyme called acid sphingomyelinase (sfin-goh-my-uh-lin-ase), or ASM. Enzymes are responsible for carrying out important processes in your body, such as breaking down fats and substances in your cells. ASM is needed to break down a fatty substance called sphingomyelin. This breakdown happens in the lysosomes within some of your cells. Lysosomes contain enzymes—including ASM.

In people with ASMD, the body is unable to make enough of the ASM enzyme. Without regular levels of ASM, sphingomyelin cannot be broken down efficiently, and instead builds up in major organs such as the liver, lungs, and spleen. This can lead to complications over time, as key organs in the body may not be able to function properly.

Explore how ASM enzyme activity affects the buildup of sphingomyelin in the cells