Gastroesophageal reflux disease (GERD): This is often considered the most common cause of persistent hiccups due to the irritation of the nerves that control breathing, which can be triggered by stomach acid flowing up into the esophagus.

Gastritis or esophagitis: Inflammation of the stomach lining or esophagus can irritate the nerves and cause hiccups.
Laryngitis: Inflammation of the larynx (voice box) can affect the nerves controlling the diaphragm, leading to hiccups.
Pneumonia: Lung infections can cause irritation of the nerves that control breathing, resulting in hiccups.
Stress or excitement: Emotional states can sometimes trigger persistent hiccups.

Myocardial infarction (heart attack): Although rare, hiccups can be a symptom of a heart attack, particularly in women, and it is crucial not to miss this diagnosis due to its severity.
Stroke or brain tumor: Neurological conditions affecting the brain's breathing centers can cause persistent hiccups.
Pneumothorax: A collapsed lung can irritate the nerves and cause hiccups, which would be a medical emergency.
Pancreatitis: Inflammation of the pancreas can cause persistent hiccups among other symptoms.

Multiple sclerosis: This chronic disease affecting the central nervous system can cause a wide range of symptoms, including persistent hiccups, due to the demyelination of nerve fibers.
Hydrocephalus: The accumulation of fluid in the brain can put pressure on the brainstem, affecting breathing control and potentially causing hiccups.
Meningitis: Inflammation of the protective membranes covering the brain and spinal cord can lead to various neurological symptoms, including hiccups.
Sarcoidosis: This inflammatory disease can affect multiple parts of the body, including the nerves, and cause persistent hiccups among other symptoms.