Table 2 Frequency of clinical findings in patients with a dominant KCNH1, KCNN3, or KCNK4 variant.

Gene	KCNH1		KCNN3		KCNK4
Total number of patients	27^a		6^b		3^c
Neurodevelopment
Mild-moderate DD	3/20	15%	4/4	100%	1/3	33%
Severe DD	18/21	86%	0/4	0%	2/3	66%
Mild-moderate ID	1/23	4%	3/3	100%	1/3	33%
Severe ID	22/23	96%	0/2	0%	2/3	66%
Hypotonia	25/27	96%	4/6	67%	2/3	66%
Seizures/epilepsy	24/27	89%	0/5	0%	2/3	66%
Skeletal abnormalities
Hypoplastic terminal phalanges of some or all fingers and/or toes	13/17	76%	6/6	100%	ND	ND
Broad thumbs and/or toes	11/24	46%	1/6	17%	ND	ND
Proximal placement and long thumb	14/18	78%	1/6	17%	ND	ND
Long great toes	15/24	63%	2/6	33%	ND	ND
Nails
Absence or hypoplasia of thumb nail	16/27	59%	5/6	83%	0/3	0%
Absence or hypoplasia of great toe nail	24/27	89%	6/6	100%	0/3	0%
Absence or hypoplasia of other fingers and/or toe nails	16/20	80%	6/6	100%	0/3	0%
Other findings
Gingival enlargement	15/19	79%	4/6	67%	3/3	100%
Hypertrichosis	3/16	19%	3/6	50%	3/3	100%

DD developmental delay, ID intellectual disability, ND no data.
^aThis study and Simons et al. [15], Kortüm et al. [14], Bramswig et al. [18], Fukai et al. [17], Megarbane et al. [16], Mastrangelo et al. [19].
^bThis study and Bauer et al. [23].
^cBauer et al. [21].

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