Among the given options, only spinal muscular atrophy presents in infancy and the rest in late childhood. Spinal Muscular atrophy (SMA) It is a degenerative disease of motor neurons, caused by the mutation of SMN gene with autosomal-recessive inheritance. Clinical features: Usually stas in infancy with hypotonia, hyporeflexia, and thin muscle mass Diagnosis: Genetic testing for SMN gene mutation. Muscle biopsy for cases of negative genetic testing. Treatment: Symptomatic and suppoive Ref: nelson textbook of pediatrics 21st edition Pgno: 3246