Hi, I am sorry for your son in law but the prognosis of the disease depends on the type, grade, stage age, of the disease and hope he is the milder type. Generally, patients tend to deteriorate over time, but prognosis varies with the SMA ( spinal muscular atrophy ) type and disease progress which shows a great degree of individual variability. The majority of children diagnosed with SMA type 0 and 1 do not reach the age of 4, recurrent respiratory problems being the primary cause of death. With proper care, milder SMA type 1 cases (which account for approx. 10% of all SMA1 cases) live into adulthood. Long-term survival in SMA1 is not sufficiently evidenced; however, recent advances in respiratory support seem to have brought down mortality. In SMA type 2, the course of the disease is stable or slowly progressing and life expectancy is reduced compared to the healthy population. Death before the age of 20 is frequent, although many patients live to become parents and grandparents. SMA type 3 has normal or near-normal life expectancy if standards of care are followed. Adult-onset SMA usually means only mobility impairment and does not affect life expectancy. Managaement is usually with the researches of gene replacement, splicing, or even activation, muscle restoration by physiotherapy, stem cell, medication doses should be given by your specialist according to the tests. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Ahmed Aly Hassan