Table 3:

Comparison of symptoms between different types of SON variants

Symptoms	All individuals		Recurring frameshift variant (n=10)		Missense/in-frame variants (n=6)		Loss of function variants (n=52)
DD/ID	58/58	100%	10/10	100%	6/6	100%	52/52	100%
Abnormal Muscle Tone	38/48	79.2%	6/10	60%	3/4	75%	35/44	79.6%
Seizures	31/50	58%	5/9	55.6%	2/4	50%	29/46	63%
Abnormal Brain MRI	40/48	81.3%	7/10	70%	0/1	0%	40/47	86.4%
Eye anomalies	33/48	68.8%	7/9	77.8%	2/5	40%	31/43	72.1%
Cardiac Defect	14/45	31.1%	5/8	62.5%	1/3	33.3%	13/42	31%
GI abnormalities	25/51	47.1%	4/10	40%	1/3	33.3%	24/48	50%
GU abnormalities	20/48	41.7%	4/10	40%	0/3	0%	20/45	44.4%
Musculoskeletal abnormalities	40/50	81.6%	8/10	80%	3/4	75%	37/46	80.4%
Short Stature	25/49	51%	5/10	50%	1/3	33.3%	24/46	52.2%
Dysmorphic features	54/57 54/56	94.7%	10/10	100%	5/6	83.3%	49/50	98%

^*n= number of individuals