Radiation therapy
Radiation therapy for cancers of the head and neck (including brachytherapy for thyroid cancers) where the salivary glands are close to or within the field irradiated is another major cause of xerostomia. A radiation dose of 52 Gy is sufficient to cause severe salivary dysfunction. Radiotherapy for oral cancers usually involves up to 70 Gy of radiation, often given along with chemotherapy which may also have a damaging effect on saliva production. This side effect is a result of radiation damage of the parasympathetic nerves. Formation of salivary gland ducts depends on the secretion of a neuropeptide from the parasympathetic nerves, while development of the end buds of the salivary gland depends on acetylcholine from the parasympathetic nerves. Sicca syndrome
"Sicca" simply means dryness. Sicca syndrome is not a specific condition, and there are varying definitions, but the term can describe oral and eye dryness that is not caused by autoimmune diseases (e.g., Sjögren syndrome). Other causes
Oral dryness may also be caused by mouth breathing, usually caused by partial obstruction of the upper respiratory tract. Examples include hemorrhage, vomiting, diarrhea, and fever.Alcohol may be involved in the cause of salivary gland disease, liver disease, or dehydration.Smoking is another possible cause. Other recreational drugs such as methamphetamine, cannabis, hallucinogens, or heroin, may be implicated. Hormonal disorders, such as poorly controlled diabetes, chronic graft versus host disease or low fluid intake in people undergoing hemodialysis for renal impairment may also result in xerostomia, due to dehydration.Nerve damage can be a cause of oral dryness.
Dermatopathia pigmentosa reticularis (DPR) is a rare, autosomal dominant congenital disorder that is a form of ectodermal dysplasia. Dermatopathia pigmentosa reticularis is composed of the triad of generalized reticulate hyperpigmentation, noncicatricial alopecia, and onychodystrophy. : 856  DPR is a non life-threatening disease that largely affects the skin, hair, and nails. It has also been identified as a keratin disorder. Historically, as of 1992, only 10 cases had been described in world literature; however, due to recent advances in genetic analysis, five additional families studied in 2006 have been added to the short list of confirmed cases. Signs and Symptoms (Presentation)
Symptoms include lack of sweat glands, thin hair, brittle nails, mottled skin, and lack of fingerprints. It is also characterized by a widespread, early-onset reticulate hyperpigmentation. Those affected may also have adermatoglyphia, abnormal epithelial differentiation, palmoplantar hyperkeratosis of the palms and soles, acral dorsal blistering, as well as hypohidrosis or hyperhidrosis.DPR is very similar to the related Naegeli-Franceschetti-Jadassohn syndrome (NFJS). Both cause an affected person to lack fingerprints, as well as present a lace-like pattern of hyperpigmentation and hyperkeratosis of the palms of the hands and soles of the feet. DPR is distinguished from NFJS by the duration of hyperpigmentation and lack of dental abnormalities. Since these differences are very slight and relatively minimal, researchers recommend that NFJS and DPR be considered a single disorder. Molecular Genetics
The disease interval for DPR was found to harbor 230 genes associated with the condition.