Table 4.

Disorders of neuromuscular transmission and differential diagnoses.

	Main clinical features	Basic treatments
Myasthenia gravis
AChR antibodies Younger females (<50y) and older males (>50y).	Generalised or more localised weakness and fatigue. Increases on repetitive activity. Thymic hyperplasia; must look for thymoma but many older patients have no thymoma or hyperplasia.	Anti-cholinesterase. Steroids and azathioprine. Plasma exchange if available
MuSK antibodies	Often more bulbar and respiratory than generalised weakness.	Anti-cholinesterases can be detrimental. Plasma exchange very effective, steroids and azathioprine not always adequate.
Lambert-Eaton Myasthenic Syndrome
VGCC antibodies	Weakness that decreases with brief tonic activity. Strongly associated with small cell lung cancer and smoking history, but some patients have no tumour and a purely autoimmune disease.	3,4-di-amino-pyridine helpful but difficult to acquire. Steroids and azathioprine as for MG.
	Often neuromuscular junction effects with weakness in ocular and respiratory muscles.	As per local guidelines
Important Differential Diagnoses a. Venoms and Neurotoxins eg. snake bite, botulism, tetanus
b. Congenital Myasthenic Syndromes	Inheritance mostly autosomal recessive but autosomal dominant in a few. Diverse neuromuscular junction gene mutations in pre and postsynaptic proteins particularly choline acetylase, Collagen Q, AChR, MuSK, DOK7 and others. Not always clinically evident in early life and older onset genetic disorders can be misdiagnosed as autoimmune MG. If suspected, refer to Rodriguez Cruz et al., 2018 for details	Treatment is symptomatic and mutation analysis is helpful in defining treatments for different forms which can respond adversely to the incorrect therapy, eg. anticholinesterase drugs make some conditions worse.