Pulmonary alveolar microlithiasis (PAM) is a disorder that prevents the lungs, and sometimes surrounding organs, such as kidneys, gallbladder, testes, and aorta, from functioning properly. Small clumps of calcium phosphate, a solid compound, form in small air sacs in the lungs (alveoli). These compartments normally exchange air within the lungs, but they cannot function properly if they are full of calcium phosphate.
Individuals with PAM have difficulty breathing and exercising. Symptoms may also include chest pain when coughing, sneezing, or breathing, and the condition gets worse with age.
PAM is caused by a changed (mutated) SLC34A2 gene. Genes are inherited in pairs, one from the mother and one from the father. This gene is responsible for regulating the production of calcium phosphate, the compound that clogs compartments in the lungs. The protein produced by this gene helps clear calcium phosphate from the lungs and without it calcium phosphate builds up.
A mutated SLC34A2 gene is inherited in an autosomal recessive manner. Autosomal recessive inheritance means that two mutated, or changed, alleles needs to be received to have this disorder. Most individuals with PAM will have parents with the condition, or their parents will be carriers, meaning they only have one mutated gene and do not show any symptoms.
Physicians can diagnose PAM based on symptoms alone, or with the help of imaging done before or after symptoms occur. Other diagnostic methods, such as x-rays, genetic testing, MRIs, and lung function studies, can also be useful. If the disease progresses, an individual’s ability to breathe decreases substantially and so lung transplantation may be be the final option.
Description Last Updated: Aug 15, 2018