Give the most probable diagnosis of a 1 year. old child of normal intelligence with features of hypotonia. On examination, there are tongue fasciculations and he keeps his body in a frog-like position –

Features of hypotonic and frog-like position suggest the diagnosis of Floppy infant syndrome. Floppy infant syndrome In FIS the baby is floppy i.e : He cannot hold his head up, there will be marked head lag as the baby is pulled up from supine to sitting posture. A normal infant, on ventral suspension (i.e. supporting the infant with a hand under the chest) keeps his back straight and head slightly up, arms abducted and knees partly flexed. A floppy infant droops, over the hand like an inverted U. Typical features Hypotonia and decreased muscular activity Frog-like posture or other unusual position at rest Delay in motor milestones Causes of Floppy infant syndrome Central nervous system Perinatal asphyxia, neonatal encephalopathy, kernicterus, cerebral palsy (atonic type), intracranial haemorrhage, chromosomal anomalies including Down syndrome and inborn errors of metabolism e.g., aminoacidurias, mucopolysaccharidosis, and cerebral lipidosis. Spinal cord lesions Anterior horn cell disease: Werdnig Hoffman spinal muscular atrophy, poliomyelitis Peripheral nerves Acute polyneuropathy, familial dysautonomia, congenital sensory neuropathy Myoneural junction Neonatal myasthenia gravis, infantile botulism, following antibiotic therapy Muscles Muscular dystrophies, congenital myotonic dystrophies, congenital myopathies (including central core disease and Nemaline myopathy), polymyositis, glycogen storage disease (Pompe's), and arthrogryposis multiplex congenital Miscellaneous Protein-energy malnutrition, rickets, Prader-Willi syndrome, malabsorption syndromes, Ehler-Danlos syndrome, cutis laxa, cretinism Coming back to question There are many causes of floppy infant syndrome. Out of the four option given in the question three of these can cause FIS - Down’s syndrome GB. syndrome Spinal muscular atrophy Spinal muscular atrophy Features of normal intelligence and tongue fasciculation's strongly suggested spinal muscular atrophy.  Down's syndrome Can be easily ruled out as intelligence is impaired in Down's syndrome. GB. syndrome Can be ruled out as it presents as an acute case with a past history of fever or viral infections. Majority of patients recover within a few days to 2 weeks.