Chronic multisymptom illness (CMI), more commonly known as Gulf War illness (GWI), is a condition that may affect as many as 30% of Gulf War veterans who were on active duty in the Southeast Asia theater of military operations beginning in August of 1990 and ending in February 1991. It also may affect troops who stayed in the area through July of 1991 performing clean-up operations, destroying chemical weapon facilities, and extinguishing oil well fires. As many as 250 000 US service members have been shown to exhibit the same cluster of symptoms. Studies report that US veterans deployed to the Persian Gulf area report worse health status than veterans serving at the same time who were deployed elsewhere. The illness has also been documented in troops from Australia and the United Kingdom who were deployed to the Gulf War in 1990-1991.

The first cases emerged in the early 1990s. No definitive cause of CMI has been identified. Epidemiologic data from the last 30 years have demonstrated several exposures associated with GWI, including nerve agents, Kuwaiti oil well fire smoke and combustion products, pyridostigmine bromide (oral medication given to service members to counteract the effects of nerve agents), and pesticides.

Case definition of CMI: There is no single, validated case definition for CMI; it is characterized by multiple, persistent symptoms (eg, fatigue, headache, arthralgias, myalgias, concentration and attention problems, and gastrointestinal disorders) across more than one body system. The symptoms must be present or frequently recur for more than 6 months and should be severe enough to interfere with daily functioning.

Patients with this illness may have concurrent diagnoses of posttraumatic stress disorder, depression, irritable bowel syndrome, chronic fatigue syndrome, and fibromyalgia. Because the cohort affected by CMI is an aging population, patients can have many other illnesses that may or may not be related to GWI.

GWI has also been referred to as Persian Gulf War syndrome and Gulf War veterans' illness.

Elements of assessment:

• Obtain a medical history and military / deployment history.
• Conduct psychosocial assessment of each patient including psychological trauma history.
• Conduct a physical examination.
• Consider diagnostic studies, as indicated, to rule out alternative diagnoses only; avoid any tests for which there may be limited additional benefit.
• Consider additional and/or longer duration encounters.

For more information, refer to the US Department of Veterans Affairs (VA) / Department of Defense (DoD) Clinical Practice Guideline on the Management of Chronic Multisymptom Illness CMI 2021.