A 52-year-old woman from Delhi presents with progressive ptosis, diplopia, and proximal muscle weakness over 3 weeks. Symptoms worsen with activity and improve with rest. Serology is positive for anti-acetylcholine receptor (AChR) antibodies. Chest CT shows no thymoma. What is the most appropriate next step in management?

Explanation

## Clinical Scenario Analysis This patient presents with **seronegative myasthenia gravis (MG)** with positive anti-AChR antibodies and no thymoma. The clinical picture is classic: ocular and bulbar symptoms progressing to generalized weakness, fatigability, and improvement with rest. ## Management Approach in Generalized MG Without Thymoma **Key Point:** In generalized anti-AChR positive MG without thymoma, the first-line pharmacological agent is an **acetylcholinesterase inhibitor** (pyridostigmine). This is the initial step before escalating to immunosuppression. ### Stepwise Management Strategy | Stage | Indication | Agent | Timing | |-------|-----------|-------|--------| | **First-line** | All MG patients | Pyridostigmine | Immediate start | | **Second-line** | Inadequate response to anticholinesterase | Corticosteroids ± azathioprine | Weeks to months | | **Third-line** | Myasthenic crisis or rapid deterioration | Plasmapheresis / IVIG | Acute setting | | **Surgical** | Thymoma present OR seronegative with poor response | Thymectomy | After medical optimization | **High-Yield:** Pyridostigmine is a reversible inhibitor of acetylcholinesterase, prolonging acetylcholine (ACh) dwell time at the neuromuscular junction and improving neuromuscular transmission. It provides symptomatic relief and allows time to assess disease severity and plan immunosuppression. **Clinical Pearl:** The absence of thymoma on imaging and positive anti-AChR serology indicates this is **non-thymomatous generalized MG**. Thymectomy is NOT indicated acutely in this setting; it is reserved for thymoma-associated MG or as a long-term option after failed medical therapy. **Mnemonic: PACI** — Pyridostigmine (first-line), Azathioprine/corticosteroids (second-line), Corticosteroids (immunosuppression), Immunoglobulin/Plasmapheresis (crisis). ## Why Pyridostigmine First? 1. **Rapid onset** of symptomatic benefit (30–60 minutes). 2. **Safe profile** with minimal systemic side effects at therapeutic doses. 3. **Allows time** to assess baseline disease severity and plan immunosuppression. 4. **Standard guideline recommendation** for initial MG management [cite:Harrison 21e Ch 385]. ## Next Steps After Initial Response If pyridostigmine alone is insufficient (residual weakness, functional impairment), introduce **corticosteroids** (prednisolone 0.5–1 mg/kg/day, tapered over months) ± **azathioprine** (1–2 mg/kg/day) for long-term disease control.