The classic presentation of COP is the development of nonspecific systemic (e.g., fevers, chills, night sweats, fatigue, weight loss) and respiratory (e.g. difficulty breathing, cough) symptoms in association with filling of the lung alveoli that is visible on chest x-ray. This presentation is usually so suggestive of an infection that the majority of patients with COP have been treated with at least one failed course of antibiotics by the time the true diagnosis is made.

"Organizing" refers to unresolved pneumonia (in which the alveolar exudate persists and eventually undergoes fibrosis) in which fibrous tissue forms in the alveoli. The phase of resolution and/or remodeling following bacterial infections is commonly referred to as organizing pneumonia, both clinically and pathologically.

Pulmonary toxicity is the medical name for side effects on the lungs.

Although most cases of pulmonary toxicity in medicine are due to side effects of medicinal drugs, many cases can be due to side effects of radiation (radiotherapy). Other (non-medical) causes of pulmonary toxicity can be chemical compounds and airborne particulate matter.

Side effects on the lungs can be very varied, and can include signs and symptoms that are either clinical, or radiological (i.e., seen on chest X-ray or CT), or both. They can include lung inflammation (pneumonitis), secondary (in this context, indirectly caused) lung infection (pneumonia), lung fibrosis, organising pneumonia (bronchiolitis obliterans organising pneumonia, BOOP), ARDS (acute respiratory distress syndrome), solitary pulmonary mass (even including lung cancer in some cases, mainly in cases of asbestos-related lung disease, but today this is very rare, because asbestos is now completely prohibited by law in most countries), or pulmonary nodule. The diagnosis should be made by a specialist, if possible.

In spite of Crohn's and UC being very different diseases, both may present with any of the following symptoms: abdominal pain, vomiting, diarrhea, rectal bleeding, severe internal cramps/muscle spasms in the region of the pelvis and weight loss. Anemia is the most prevalent extraintestinal complication of inflammatory bowel disease. Associated complaints or diseases include arthritis, pyoderma gangrenosum, primary sclerosing cholangitis, and non-thyroidal illness syndrome (NTIS). Associations with deep vein thrombosis (DVT) and bronchiolitis obliterans organizing pneumonia (BOOP) have also been reported. Diagnosis is generally by assessment of inflammatory markers in stool followed by colonoscopy with biopsy of pathological lesions.

The chief types of inflammatory bowel disease are Crohn's disease and ulcerative colitis (UC). Inflammatory bowel diseases fall into the class of autoimmune diseases, in which the body's own immune system attacks elements of the digestive system.

Accounting for fewer cases are other forms of IBD, which are not always classified as typical IBD:

- Microscopic colitis subdivided into collagenous colitis and lymphocytic colitis

- Diversion colitis

- Behçet's disease

- Indeterminate colitis

No disease specific markers are currently known in the blood, enabling the reliable separation of Crohn's disease and ulcerative colitis patients. The way doctors can tell the difference between Crohn's disease and UC is the "location" and "nature" of the inflammatory changes. Crohn's can affect any part of the gastrointestinal tract, from mouth to anus ("skip lesions"), although a majority of the cases start in the terminal ileum. Ulcerative colitis, in contrast, is restricted to the colon and the rectum.

Microscopically, ulcerative colitis is restricted to the mucosa (epithelial lining of the gut), while Crohn's disease affects the full thickness of the bowel wall ("transmural lesions"). Lastly, Crohn's disease and ulcerative colitis present with extra-intestinal manifestations (such as liver problems, arthritis, skin manifestations and eye problems) in different proportions.

In 10–15% of cases, a definitive diagnosis neither of Crohn's disease nor of ulcerative colitis can be made because of idiosyncrasies in the presentation. In this case, a diagnosis of indeterminate colitis may be made. Although a recognised definition, not all centres refer to this.

Traditionally there have been 5 components that form the chiropractic subluxation. The vertebral subluxation complex is differentiated by the fifth component, general systemic disturbances secondary to the spinal misalignment (vertebral subluxation).

1. Spinal Kinesiopathology

2. Neuropathophysiology/Neuropathology

3. Myopathology

4. Histopathology

5. Pathophysiology/Pathology

In chiropractic, vertebral subluxation is a purported misalignment of the spinal column, not necessarily visible on X-rays, leading to a set of signs and symptoms sometimes termed vertebral subluxation complex. It has no biomedical basis, lacks clinical meaningfulness, and is categorized as pseudoscientific by leading chiropractic authorities. Traditionally, the "specific focus of chiropractic practice" is the chiropractic subluxation and historical chiropractic practice assumes that a vertebral subluxation or spinal joint dysfunction interferes with the body's function and its innate intelligence, as promulgated by D. D. Palmer, the inventor of chiropractic.

The chiropractic subluxation is the heart of the split between "straight" and "mixer" chiropractors. Straight chiropractors continue to follow Palmer's vitalistic tradition, claiming that subluxation has considerable health effects and also adding a visceral component to the definition, while mixers, as exemplified by the United Kingdom's General Chiropractic Council, consider it a historical concept with no evidence identifying it as the cause of disease.

Within the chiropractic tradition, a vertebral subluxation complex is believed to be a dysfunctional biomechanical spinal segment which actively alters neurological function, which in turn, is believed to lead to neuromusculoskeletal and visceral disorders. The WHO acknowledges this difference between the medical and chiropractic definitions of a subluxation: medical doctors only refer to "significant structural displacements" as subluxations, whereas chiropractors suggest that a dysfunctional segment, whether displaced significantly or not, should be referred to as a subluxation. This difference has been noted in the proceedings of the chiropractic profession's "Mercy Center Consensus Conference": "The chiropractic profession refers to this concept as a 'subluxation'. This use of the word "subluxation" should not be confused with the term's precise anatomic usage, which considers only the anatomical relationships."

The chiropractic vertebral subluxation complex has been a source of controversy since its inception in 1895 due to the lack of empirical evidence for its existence, its metaphysical origins, and claims of its far reaching effects on health and disease. Although some chiropractic associations and colleges support the concept of subluxation, many in the chiropractic profession reject it and shun the use of this term as a diagnosis. In the United States and in Canada the term "nonallopathic lesion" may be used in place of "subluxation".

A 2009 review concluded that epidemiologic evidence does not support the chiropractic subluxation, concluding:

In 2015, internationally accredited chiropractic colleges from Bournemouth University, University of South Wales, University of Southern Denmark, University of Zürich, Institut Franco-Européen de Chiropraxie, and University of Johannesburg made an open statement which included: "The teaching of the vertebral subluxation complex as a vitalistic construct that claims that it is the cause of disease is unsupported by evidence. Its inclusion in a modern chiropractic curriculum in anything other than an historic context is therefore inappropriate and unnecessary".