. Penicillamine-induced myasthenia - is similar to adult myasthenia gravis, and usually resolves over several months after drug withdrawal. 5. Congeni

: Main groups of acquired myasthenia gravis GROUP I: Early onset (<40>40 years); weakness generalized or ocular only; incidence higher in men; thymic atrophy/involution; anti-AChR antibody titres low: GROUP IV: Seronegative; weakness ocular only or generalized; thymic atrophy/involution; anti-AChR antibodies absent, but auto-antibodies to other muscle cell targets are implicated Investigations. 1. Anti-AChR antibody (AchRAb) - Titre elevated in 90% of patients with generalized myasthenia. 2. Anti-striated muscle antibody - detectable in over 90% with thymoma and in about 30% of other patients. 3. Edrophonium chloride (Tensilon) test -necessary: if (a) Diagnosis has to be made immediately because of disease severity. (b) Patient -is sero-negative for anti-AChR antibodies. If no side-effects develop after IV test dose of 1 -2 mg, further 5-8 mg is injected. Positive response consists of obvious improvement in strength within 1 minute. This test can be combined with EMG. 4. Electrodiagnosis- (a) Repetitive nerve stimulation - Electrical stimuli are given at rate of 3/sec., and action potentials recorded from surface electrodes over muscles. A rapid reduction in amplitude of evoked muscle action potential is considered a positive response. (b) EMG studies - include recording the response to nerve stimulation and single muscle fibre studies (SF-EMG). 5. CXR and CT or MRI - for thymoma. If negative initially, it should be