Primary neural leprosy: clinical, neurophysiological and pathological presentation and progression

Area of Science:

• Neurology
• Infectious Diseases
• Dermatology

Background:

• Leprosy-related disability stems from peripheral nervous system damage.
• Primary neural leprosy, lacking skin manifestations, is an underdiagnosed subtype.
• Understanding disease progression is key for early recognition and intervention.

Purpose of the Study:

• To evaluate clinical, neurophysiological, and laboratory findings in primary neural leprosy patients.
• To compare disease characteristics based on short (≤12 months) versus long (>12 months) duration.
• To elucidate the progression of nerve damage in primary neural leprosy.

Main Methods:

• Retrospective analysis of 164 patients with definite or probable primary neural leprosy.
• Clinical assessment of symptoms, neurological deficits, and nerve thickening.
• Neurophysiological testing and laboratory investigations.

Main Results:

• Small-fiber neuropathy (positive/negative symptoms) was present in ~95% of patients at presentation, often starting in upper limbs.
• Deep sensory modalities and large-fiber (sensory/motor) damage were more frequent in patients with longer disease duration (>12 months).
• Grade-2 disability and nerve thickening were significantly higher in patients with chronic disease (P < 0.001).

Conclusions:

• Primary neural leprosy exhibits significant phenotypic variability and progresses over time.
• Early-stage disease (<12 months) predominantly involves small-fiber sensory neuropathy.
• Chronic disease (>12 months) presents as asymmetrical sensory-motor neuropathy with reflex abnormalities, indicating later large-fiber involvement.