Convert to ICD-10-CM: 
335.21 converts approximately to:
- 2015/16 ICD-10-CM G12.21 Amyotrophic lateral sclerosis
 ICD-9-CM Volume 2 Index entries containing back-references to 
335.21:
- Amyotrophia, amyotrophy, amyotrophic 728.2  spinal progressive 335.21 spinal progressive 335.21
 
- Atrophy, atrophic Aran-Duchenne muscular 335.21 Aran-Duchenne muscular 335.21
  Cruveilhier's 335.21 Cruveilhier's 335.21
  Duchenne-Aran 335.21 Duchenne-Aran 335.21
 
- Creeping palsy 335.21 palsy 335.21
  paralysis 335.21 paralysis 335.21
 
- Cruveilhier's disease 335.21
- Disease, diseased - see also Syndrome Cruveilhier's 335.21 Cruveilhier's 335.21
  wasting NEC 799.4 wasting NEC 799.4   due to malnutrition 261 due to malnutrition 261 
  paralysis 335.21 paralysis 335.21
 
 
- Duchenne-Aran myelopathic, muscular atrophy (nonprogressive) (progressive) 335.21
- Palsy (see also Paralysis) 344.9  creeping 335.21 creeping 335.21
  wasting 335.21 wasting 335.21
 
- Paralysis, paralytic (complete) (incomplete) 344.9  atrophic 356.9 atrophic 356.9   infantile, acute (see also Poliomyelitis, with paralysis) 045.1 infantile, acute (see also Poliomyelitis, with paralysis) 045.1 
  muscle NEC 355.9 muscle NEC 355.9 
  progressive 335.21 progressive 335.21
  spinal (acute) (see also Poliomyelitis, with paralysis) 045.1 spinal (acute) (see also Poliomyelitis, with paralysis) 045.1 
 
  creeping 335.21 creeping 335.21
  muscular (atrophic) 359.9 muscular (atrophic) 359.9   progressive 335.21 progressive 335.21
 
  progressive 335.21 progressive 335.21
  wasting 335.21 wasting 335.21
 
- Poliomyelitis (acute) (anterior) (epidemic) 045.9  chronic 335.21 chronic 335.21
 
- Wasting palsy, paralysis 335.21 palsy, paralysis 335.21