1B20.20

ICD-11 MMS 2026-01

Type I leprosy reaction

Description

This phenomenon, also named “upgrading reaction,” occurs in borderline leprosy states and is associated with an increase in cell-mediated immunity. It occurs typically within the first 6 months of treatment in previously untreated patients but may be related to stress, intercurrent infections, or pregnancy. Clinical features include inflammatory swelling, erythema and occasionally ulceration of existing lesions, constitutional symptoms and neuritis. If the neuritis is not treated promptly permanent motor nerve damage may ensue.

Index terms

  • Type I leprosy reaction
  • Leprosy reversal reaction
  • Leprosy upgrading reaction

Exclusions from above levels

  • NE83.1 – Infection arising from device, implant or graft, not elsewhere classified

Sibling codes

  • 1B20.21 – Type II leprosy reaction

Foundation entity

Type I leprosy reaction – http://id.who.int/icd/entity/1185467033

Allowed postcoordination axes

Part of: 1B20.2: Leprosy reactions › 1B20: Leprosy › 01: Certain infectious or parasitic diseases