Reduced muscle phosphorylase kinase activity

What it means

Activity of the enzyme muscle phosphorylase kinase (PhK) in muscle tissue below the lower limit of normal.

The enzyme PhK comprises four copies each of four subunits (alpha, beta, gamma, and delta).

Rare diseases that can present with this1

The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.

Part of the broader category