Pulmonary alveolar microlithiasis (PAM) is a rare, inherited disorder of lung phosphate balance that is associated with small stone formation in the airspaces of the lung. Mutations in the gene SLC34A2 result in loss of a key sodium, phosphate co-transporter (called Npt2b), known to be expressed in distal alveolar type II cells, as well as in the mammary gland, and to a lesser extent in intestine, kidney, skin, prostate and testes. As the disease progresses, the lung fields become progressively more dense (white) on the chest xray, and low oxygen level, lung inflammation and fibrosis, elevated pressures in the lung blood vessels, and respiratory failure ensue, usually in middle age. The clinical course of PAM can be highly variable, with some patients remaining asymptomatic for decades, and others progressing more rapidly. There is no effective treatment, and the mechanisms of stone formation, inflammation and scarring are not known. Signs and symptoms
Patients typically have no symptoms until the third or fourth decade of life. In most cases, the disease is discovered incidentally on routine chest Xray. The most common symptoms include the following:
dyspnea
dry cough
chest pain
sporadic hemoptysis
asthenia
pneumothoraces

Genetics
PAM is hereditary and another involved family member can be identified in 36% to 61% of cases. Impaired activity of the SLC34A2 gene is responsible for PAM.The SLC34A2 gene encodes a membrane protein that is expressed primarily in the apical portions of alveolar type II cells and is the most abundant phosphate carrier in the lungs.
Delsym is an American brand of cough medicine owned by Reckitt, and manufactured at Unither Manufacturing in Rochester, NY. It is different from most brands of cough medicine in that the active ingredient is "time released". The time release feature allows the drug to suppress the cough reflex for a longer period of time. The active ingredient per teaspoon (5 mL) is dextromethorphan polistirex, equivalent to dextromethorphan HBr 30 mg. Method of action
The active ingredient, dextromethorphan (metabolized to dextrorphan), is surrounded by an edible plastic called polistirex. When the Delsym arrives in the stomach, an initial amount of dextromethorphan is immediately released into the bloodstream while the rest is surrounded by a plastic that is slowly dissolved by stomach acid. After the polistirex is dissolved sufficiently, more dextromethorphan is released. Recreational use
Intentionally consuming more than the recommended dosage of Delsym may result in euphoria, lack of coordination, hallucinations, apathy, feelings of dissociation, and disorientation. This is due to dextromethorphan as well as its pharmacologically-active metabolite dextrorphan, both dissociative drugs that work as NMDA receptor antagonists the same way nitrous oxide (N2O), ketamine, and phencyclidine (PCP) do. Because of the abuse potential, many pharmacies and large retail chains have begun taking precautions such as restricting sales to those under age 18 and limiting the number of sales of dextromethorphan-containing products per customer. References
External links
Official website