A woman presents with bilateral chronic ocular surface disease. Schirmer test I shows 3 mm wetting at 5 minutes. Rose Bengal staining reveals interpalpebral staining. She has rheumatoid arthritis. Which pathophysiological sequence best explains the immune mechanism underlying dry eye in Sjogren syndrome?
- A IgG immune complex deposition in lacrimal gland acini causing membranous nephropathy-like damage
- B Muscarinic M3 receptor antibodies blocking lacrimal gland secretomotor nerve signaling ✓
- C Direct T-cell cytotoxicity to melanocytes within the lacrimal gland
- D Complement activation via lectin pathway destroying aqueous secretory cells
Correct answer: B. Muscarinic M3 receptor antibodies blocking lacrimal gland secretomotor nerve signaling
Explanation
In Sjogren syndrome, anti-Ro/SSA and anti-La/SSB antibodies are classic serological markers, but functional glandular impairment is mediated significantly by anti-muscarinic M3 receptor antibodies. These autoantibodies block cholinergic (parasympathetic) stimulation of lacrimal and salivary gland acinar cells, impairing aqueous secretion. CD4+ T-cell infiltration (lymphocytic sialadenitis/dacryoadenitis with focus score ≥1) contributes to acinar destruction. The M3 mechanism explains why some patients show secretory dysfunction disproportionate to glandular destruction.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.