[Myasthenia gravis in AIDS and neurosyphilis]

The co-occurrence of myasthenia gravis and AIDS in a 38 year old drug addict with HIV-infection is reported. The diagnosis "myasthenia gravis" is based on clinical features with muscle weakness worsening with exercise and depending on the time of day, and secondly on the result of electrophysiological tests, with a typical decrement in repetitive nerve conduction study, and on the presence of antibodies to acetylcholine receptors. A co-existing neurosyphilis was treated intravenously with penicillin G, resulting in good improvement of the associated myopathy. The remaining muscle weakness responded well to treatment with pyridostigmine bromide started after the end of the antibiotic therapy. A tumor in the anterior mediastinum measuring 3 by 2 cm was diagnosed by CT scan and removed, histology showed normal thymus tissue. After operation the patient became asymptomatic on treatment with low dosage pyridostigmine (3 x 30 mg). The association of myasthenia gravis with AIDS may derive from an alteration of the immune system based on changes in the thymus gland. Differential diagnosis in AIDS patients with generalized weakness should include a myasthenic reaction.