Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Pulmonary alveolar microlithiasis ?
    ### Response:
    Pulmonary alveolar microlithiasis is a disorder in which tiny fragments (microliths) of calcium phosphate gradually accumulate in the small air sacs (alveoli) of the lungs. These deposits eventually cause widespread damage to the alveoli and surrounding lung tissue (interstitial lung disease).
    