Table 1 Summary of clinical features and disease associations.

	Total	Children		Adults
		AChR Ab‐ positive*	AChR Ab‐negative*	AChR Ab‐positive*	AChR Ab‐negative*
Total		127	70	127	64
F:M		76:51	29:41	76:51	34:30
Maximum MGFA grade, n
1	227	103	54	31	39
2a	50	11	10	19	10
2b	53	10	2	30	11
3a	5	0	1	3	1
3b	34	3	2	26	3
4a	4	0	1	3	0
4b	6	0	0	6	0
5	9	0	0	9	0
Thymic pathology (MRI), n
Normal†		98	52	63	48
Thymitis		26	18	29	12
Thymoma		3	0	35	4
Hyperthyroidism		16	5	16	17

Ab, antibody; AChR, acetylcholine receptor; F, female; M, male; MGFA, Myasthenia Gravis Foundation of America.

*Most of the AChR antibodies were not measured at the time of maximum disease severity.

†Normal refers to normal for age at the time of MRI; this would include adults with thymic atrophy.