A37.91 Whooping cough, unspecified species with pneumonia

Billable ICD-10-CM code, FY2026. Acts as a Major Complication or Comorbidity (MCC) as a secondary diagnosis.

MS-DRG index

Defines the logic of DRG(s) 202-203 in MDC 04.

Approximate ICD-9-CM (GEMs)

• 033.9 Whooping cough, unspecified organism (approximate)
• 484.3 Pneumonia in whooping cough (approximate)

Code annotations containing back-references to A37.91

Back-references to A37

• Type 1 Excludes: J17 Pneumonia in diseases classified elsewhere ("whooping cough with pneumonia (A37 with fifth-character 1)")

Diagnosis Index entries for A37.91

• Pneumonia (acute) (double) (migratory) (purulent) (septic) (unresolved) › in (due to) › whooping cough
• Whooping cough › with pneumonia

Nearby codes

• A37.8 Whooping cough due to other Bordetella species
• A37.80 Whooping cough due to other Bordetella species without pneumonia
• A37.81 Whooping cough due to other Bordetella species with pneumonia
• A37.9 Whooping cough, unspecified species
• A37.90 Whooping cough, unspecified species without pneumonia
• A37.91 Whooping cough, unspecified species with pneumonia (this code)