Based on the information provided, I cannot directly name the illness causing a Lipitor dose change as the question does not specify a particular context or situation. However, I can provide some general information about Lipitor and possible reasons for dose changes.

Lipitor, also known as atorvastatin, is a prescription medication used to treat high cholesterol levels and prevent cardiovascular disease [1]. It belongs to a class of drugs called statins, which work by reducing the amount of cholesterol produced by the liver [1].

There are several reasons why a healthcare provider might adjust a patient's Lipitor dose. These reasons may include:

1. Changes in the patient's condition: If a patient's cholesterol levels or risk of cardiovascular disease changes, their healthcare provider may adjust their Lipitor dose accordingly.
2. Adverse reactions: If a patient experiences adverse reactions to Lipitor, such as muscle pain or liver problems, their healthcare provider may adjust their dose or recommend a different medication [1].
3. Drug interactions: Lipitor can interact with other medications, which may affect its effectiveness or increase the risk of adverse reactions. In these cases, a healthcare provider may adjust the Lipitor dose or recommend alternative treatments [1].

It's important to note that any changes to a patient's medication regimen should be made in consultation with a healthcare provider.

Sources:
[1] DrugPatentWatch.com. (n.d.). Atorvastatin (Lipitor). Retrieved from <https://www.drugpatentwatch.com/drugs/atorvastatin>