CSS is a progressive disease consisting of three distinct phases: the allergic stage, the hypereosinophilic stage and the vasculitic stage. With early diagnosis and effective treatment, not everyone diagnosed with Churg Strauss Syndrome experiences all three phases, or experiences them sequentially.

The first stage is often called the prodromal phase. Prodromal simply means symptoms that occur at the onset of a disease. This first, allergic phase, is almost always characterized by asthma. Often the individual develops asthma late in life. This is called late onset asthma. Some people who have had asthma throughout their lives experience a worsening of symptoms that become more difficult to treat. Sinus disease, which is characterized by facial pain from sinusitis, nasal polyps, allergic rhinitis (inflammation of the mucous membranes of the nose causing sneezing, itching, runny nose) and recurrent pneumonia and/or bronchitis are also typical of this prodromal phase. This phase can last from 4 to 27 months, although some patients stay in this phase for many years.

The next phase is called the hypereosinophilic phase. Hypereosinophilia means there is an overabundance of a certain white blood cell called an eosinophil. This overabundance of eosinophils can occur either in the blood or in the tissues. Often during this phase, patients suffer from chronic eosinophilic pneumonia and eosinophilic gastroenteritis (inflammation of the esophagus, stomach or intestines). The symptoms during this phase can include feeling generally unwell with weight loss, fever, and night sweats. In addition if the lungs are affected, the patient may experience shortness of breath, a feeling of heaviness in the chest and a constant cough. If the gastrointestinal tract is involved people may experience abdominal pain, bloating, vomiting, diarrhea, and nausea. Inflammation of the esophagus may cause dysphagia, or difficulty swallowing. Many people with eosinophilic gastroenteritis find it very difficult to eat. They often experience increasing and sometimes very severe pain after meals. After eating they may experience bouts of vomiting and/or diarrhea, sometimes resulting in weight loss and even anorexia. Some patients get ulcers. Patients may stay in the this second phase for months or years. During this time, their symptoms may become less severe and may even go away, only to recur. Some people experience the second and third phases simultaneously. With treatment and medication some folks never even get to the third phase which is:

The systemic vasculitis phase. Systemic vasculitis means that there may be inflammation and damage to blood vessels throughout the body. This, in turn, may cause damage to many different organs. Because CSS can affect so many different organs at this stage, symptoms vary widely depending on the organ affected. General symptoms include fever, weight loss and adenopathy (enlargement of the glands, especially the lymph glands). Common organs affected by CSS include the skin, the heart, the lungs, the central nervous system, the peripheral nervous system, the gastrointestinal tract and less commonly, the kidneys, the eyes and the musculoskeletal system.

CSS involving the skin can manifest itself in many way. Rashes, purpura (purplish discolorations caused by bleeding vessels near the surface of the skin) or nodules (solid raised bumps of more than 10 millimeters in diameter) are common. In addition, livedo reticularis (a blotchy mottling of the skin), urticaria (raised red welts) and vesicles (small fluid filled blisters) might occur.

If the lungs are involved the following symptoms might be present: cough, shortness of breath, hemoptysis (coughing up blood stained sputum), rales (small clicking, bubbling or rattling sounds in the lung), rhonchi (chest sounds that sound like snoring) and a feeling of pressure in the chest.

If the disease progresses to the heart the CSS patient might experience fatigue, dyspnea (shortness of breath), chest pain, irregular heartbeat, increased blood pressure, difficulty in breathing except when upright, swollen legs, appetite loss and fainting episodes. Some of these symptoms are related to pericarditis, which is inflammation of the sac-like covering of the heart, where others are related to congestive heart failure. Heart problems are a leading cause of death in Churg Strauss Syndrome.

Involvement of the central nervous system, or the brain, might cause intellectual or motor disturbances, seizures, confusion, difficulty in speaking and headaches. Cerebral hemorrhage is a cause of death in Churg Strauss Syndrome and usually occurs in patients who also have hypertension.

Patients more commonly have problems associated with the peripheral nervous system, such as peripheral neuropathy, including mononeuritis multiplex. Symptoms occur in the limbs and include feelings of numbness or hypoesthesia, and hyperesthesia , which is an increased sensitivity to any stimulation and can be experienced as tingling or a burning pain. Other symptoms include abnormal sensations, and difficulty in moving a part of the body. Some people experience foot drop. Patients with foot drop cannot lift up the ankle, straighten or extend the toes, or turn the foot outward.

Gastrointestinal problems occur in approximately 40% to 60% of patients whose disease progresses to the vasculitic phase. The main symptoms are severe abdominal pain, bloody diarrhea, vomiting and nausea. The symptoms may be the same or similar to those of eosinophilic gastroenteritis. Some patients may develop obstructions or perforated intestines. 

Involvement of the musculoskeletal system may result in swelling of the joints, muscle pain and arthritis.

Kidney involvement is not common in CSS. If the kidneys themselves are damaged there might not be any symptoms at all. Tests, however might show there to be blood or protein in the urine. Sometimes kidneys can be damaged by obstructive uropathy which occurs when urine cannot drain through a ureter because of a blockage, causing urine to back up into the kidney. Symptoms of kidney involvement include fever, urinary tract infection, nausea, edema (swelling), and difficulty or pain while urinating.

Although not common, the optic nerve can be affected by vasculits causing eye pain and vision problems.

During the vasculitic phase patients may be anemic or have low platelet counts, resulting in weakness and fatigue.

In addition to all the possible symptoms caused by Churg Strauss Syndrome in any of the three phases, patients might also experience the general effects of anyone who has a a chronic illness, such as depression, fatigue and general malaise. In addition, the medications used to treat the disease may also cause side effects. Treatment sometimes causes the immune system to be suppressed leading to a greater vulnerability to all sort of illnesses, including a greater susceptibility to pneumonia. CSS is a type of vasculitis and people with vasculitis have an increased risk of blood clots. Because it is often hard to sort out what is disease, what are the effects of medications, and what is something else all together, it is helpful to keep a medical journal to keep track of symptoms, problems and concerns for discussion with your doctors.

It is easy to feel overwhelmed and discouraged after reading about all the possible problems associated with having Churg Strauss Syndrome, but it is essential to remember that: 1) with early diagnosis and treatment, many people never experience the vasculitic phase of the disease, 2) with effective treatment most of the symptoms in any of the three phases can be relieved, and 3) researchers are working to achieve a greater understanding of the disease which will lead to better treatment and possibly, a cure.