Histopathological Diagnosis of Leprosy Type 1 Reaction with Emphasis on Interobserver Variation

Area of Science:

• Dermatology
• Pathology
• Infectious Diseases

Background:

• Leprosy reversal reaction (RR) is an acute inflammatory complication of leprosy.
• Discrepancies exist in diagnosing RR between clinicians and pathologists, compounded by inter-observer variability among pathologists.
• There is a lack of universally agreed-upon diagnostic criteria for RR in histopathology.

Purpose of the Study:

• To assess clinicopathological correlation in diagnosing leprosy reversal reactions (RR).
• To evaluate inter-observer agreement among pathologists in identifying RR histopathologically.
• To identify reliable histopathological features for diagnosing RR.

Main Methods:

• 120 leprosy biopsies and H&E stained slides were reviewed by three independent pathologists.
• Pathologists were blinded to clinical diagnosis and each other's assessments.
• Histopathological findings were analyzed for correlation with clinical diagnosis and inter-observer agreement using Kappa statistics.

Main Results:

• Discordance between clinical and histopathological diagnoses ranged from 23.7% to 34.5%.
• Consistent histopathological findings across observers included dermal edema, intragranuloma edema, and epidermal erosion.
• Kappa statistics indicated good inter-observer agreement among the pathologists (κ = 0.61–0.83).

Conclusions:

• Leprosy reversal reactions (RR) may be underdiagnosed on histopathological examination.
• Dermal edema, edema within the granuloma, and partial obliteration of the grenz zone by granuloma are reliable histopathological indicators for diagnosing RR.