Muscle specific tyrosine kinase (MuSK) myasthenia gravis (MG) is a rare subtype of MG, which is immunologically distinct and differential therapeutic response. Though MG is often associated with other autoimmune disorders or malignancy, concurrence of other disease and MuSK MG has been infrequently reported. We present a patient of MuSK MG associated with multicentric Castelman disease.