Authors’ reply

Sir,

We agree with Moslehi[1] that there is no known effective treatment for Pulmonary Alveolar Microlithiasis (PAM) and the same has been discussed in the review.[2] In the letter to the editor, the author has discussed an anecdotal case report where steroids have been beneficial and the treatment with daily prednisolone for 6 months showed improvement in wheezing and chest tightness, but symptoms recurred when it was discontinued.[3] It suggested the possibility of coexistence of reversible obstructive lung disease. In the other case,[4] the benefit of hydroxychloroquine along with corticosteroid cannot be attributed to the particular drug on the basis of an isolated case report. It is clear that no definite treatment is available till date and, therefore, the long-term prognosis remains bleak.

Mutation in the SLC34A2 gene, which encodes the type IIb sodium-phosphate co-transporter seems to be accountable for the pathogenesis of intra-alveolar accumulation of phosphate leading to formation of microliths.[2]

Future therapy for PAM should be aimed to exploit the annulling the mechanism of inhibition of protein transporting the phosphorus ion from the alveolar space into type II alveolar cells and the inability of type II alveolar cells to clean up the phosphorus ion from the alveolar space and in the process halting the accumulation of calcium and phosphorus rich microliths in the alveoli. Activation of such a mechanism can be the clue towards the development of new area of research for the treatment of PAM.