Older cats who are suddenly averse to exercise or who breathe shallowly and/or rapidly may have a buildup of calcium nodules in their lungs. Diagnosis of this requires X-ray examination, and treatments tend to be more about making your cat comfortable than curing the condition.

Calcium buildup, when found in the lungs, is also called pulmonary mineralization. This can happen as a result of localized trauma to a singular area, or in a more diffuse way that affects much of the lung tissue. This disease is often idiopathic, meaning that it has no definite cause. Symptoms can range from nothing to severe respiratory distress. However, as it gets worse, the calcium deposits can make naturally flexible lung tissue rigid. It is most common in older cats, and can be a secondary symptom of a primary disease.

There are many cases in which a calcium buildup in the lungs offers no symptoms at all. The severity of symptoms can range anywhere from mild to extreme. They can include:

This condition, along with calcification in many of the other soft tissues in cats, does not have one specific cause. Localized calcifications are often an immune response to a singular area of physical trauma or infection. Diffuse mineralization, however, is often hard to understand. It can appear alone or it can be a secondary symptom of several primary diseases. Commonly known causes include: 

An X-ray and a blood test are typically the first two things that a vet will do to try and diagnose any form of lung distress. Chest X-rays can measure the amount of calcification, whether it is diffuse or localized, and if there are causes located directly in the lungs, like bronchial stones. From there, a urinalysis and a lung biopsy of calcified tissue can further narrow down whether the cause is due to something fungal, cancer-related, or hormonal. If the images that an X-ray provides are insufficient, the vet may want to do a CT scan. At this point, they will likely look at additional soft tissues to see if the mineralization is only in the lungs or if it is the heart and other internal organs. Many conditions that can cause pulmonary mineralization do not limit the calcium deposits to lungs alone, but instead will spread them into many of the body's soft tissues. If a fungal or other infection is suspected to be linked to the problem, then the vet may biopsy a lymph node to look for infective agents that may have a role in the calcification. 

It is relatively easy to treat localized calcium buildup with a biopsy or minor surgery. However, diffuse mineralization has no known cure. Treatments tend to focus on management of a primary condition or on easing any respiratory distress.

If there are localized calcium nodules in the lungs, it is possible to remove them in a minor surgery, provided they are only in one or two locations. This is not a viable option for diffuse mineralization. Surgery may be worthwhile from a cost and invasiveness standpoint if it is able to be done in a few hours of outpatient surgery. However, the more complicated the surgery, the higher the risk and the cost.

Metastatic lung cancer or other cancers can have calcium mineralization in the lungs as a secondary symptom. If the cancer is treated, it may cause a reversal of the mineralization, or at least it will stop additional calcium deposits. 

If your cat has an adrenal tumor causing high levels of cortisol, then removing the adrenals may solve the issue, and can often be much easier to solve than metastatic cancer. 

Fungal infections may cause calcium buildups in the lungs of cats as well as the other organs and soft tissues. Though they can be time-consuming and difficult to treat, there are antifungal medications that are not overly expensive and which only require you to give your cat oral medication one to three times daily. 

Calcium buildup is often linked to autoimmune diseases, and it can be lessened by regular doses of corticosteroids. The duration of time and dose of steroids will depend on the severity of the case and the advice of your vet.

In some cases, the buildup may be considered untreatable. If this is the case, the vet may offer some form of medication to either ease pain or aid breathing. The goal, in this case, will simply be to make your cat as comfortable as possible.

Many forms of diffuse calcium buildup in the lungs are neither curable nor treatable. If the cat has one of these forms of mineralization, then there will likely be regular follow-up visits to ensure that medications for comfort are working. However, in the case of management through curing a primary illness, then recovery is based on how easy the primary condition is to cure. Fungal infections are easier to cure than cancer, for example, and have a much more likely chance of full recovery without need for follow-up. Prognosis is highly variable from cat to cat, and from cause to cause.