A 24-year-old Sri Lankan woman with drug resistant focal dyscognitive seizures experienced daily seizures despite treatment with carbamazepine 800 mg twice daily and clonazepam 2 mg twice daily. She was on no other medication and otherwise well. Lamotrigine was started with the aim of improving seizure control and slowly titrated to a dose of 150 mg in the morning and 200 mg in the evening over a period of 6 months. Her seizure frequency reduced.
Fifteen months after initiation of lamotrigine, she complained of productive cough with yellow sputum. She was afebrile. Chest examination was normal. Lymphadenopathy was detected in the right cervical chain. Other lymph nodes, tonsillar tissue and spleen were of normal size. Spirometry was within normal limits. High resolution CT chest and neck showed extensive bilateral cervical lymphadenopathy and patchy ground-glass nodules in multiple lobes but no intrathoracic adenopathy. Full blood count, serum chemistries, as well as testing for rheumatoid factor, anti-citric citrullinated peptide antibodies, antinuclear antibodies, human immunodeficiency virus, Epstein-Barr virus, cytomegalovirus, toxoplasma and tuberculosis were all normal or negative. Erythrocyte sedimentation rate and c-reactive protein were elevated at 95 mm/h (normal < 23 mm/h) and 16 mg/L (normal < 5 mg/L) respectively. Histology of an excisional lymph node biopsy showed reactive follicular hyperplasia with capsular thickening without malignancy or granuloma. A review of prior blood testing revealed intermittent low-grade eosinophilia since introduction of lamotrigine (see Table 1). A diagnosis of lamotrigine-related pseudolymphoma was made. Lamotrigine was gradually withdrawn and her lymphadenopathy and pulmonary findings (which also likely represented a medication toxicity) have resolved.