A 1 yr old child is with normal intelligence with features of hypotonia. On examination there are tongue fasciculations and he keeps his body in a frog like position and also loss of reflexes. Give the most probable diagnosis?

Spinal muscular atrophy type 1 (Werdnig-Hoffman disease) is the most common cause of a floppy infant syndrome. Children may attain typical "frog posture" or other postures on rest. Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder in which anterior horn cells in the spinal cord degenerate. Three clinical subtypes are recognized: SMA I: The most devastating. Mild weakness may be present at bih but is clearly evident by 3 months and is accompanied by loss of reflexes and fasciculations in affected muscles. Progression of the disorder leads to eventual respiratory failure, usually by age 1 year. SMA II: Symptoms of SMA II begin later, with weakness and decreased reflexes generally apparent by age 2 years. SMA III: Children affected with SMA III begin to become weak as they approach adolescence. Ref: Tsaic A.C., Manchester D.K., Elias E.R. (2012). Chapter 37. Genetics & Dysmorphology. In W.W. Hay, Jr., M.J. Levin, R.R. Deterding, J.J. Ross, J.M. Sondheimer (Eds), CURRENT Diagnosis & Treatment: Pediatrics, 21e.