Objective:

Examine functional impairments in patients with KCNQ2-DEE and associations among key clinical features.

Background:

KCNQ2-DEE is a rare, heterogenous condition that manifests as developmental delays combined with neurological comorbid signs and symptoms.   While seminal work has described KCNQ2-DEE patients at the group-level, relatively little information is available about the severity and variability of the condition within individuals.

Design/Methods:

Data obtained from a cross-sectional survey (2018-2020) of parents of children aged 2 years and above with KCNQ2-DEE was analyzed across 4 functional ability domains (mobility, communication, hand use, and eating abilities). Each of these aspects was considered core to the condition and clinically meaningful to families. The functional domains were assessed with classifications systems commonly employed in the pediatric rehabilitation field. The associations of severe functional impairment across these domains and the number of domains with severe impairment were examined to determine which, if any, impairments tended to occur in isolation or in combination with other impairments. Data were analyzed with methods appropriate for nonparametric dichotomous and ordinal data.

Results:

Communication impairment and eating dependencies were apparent across the vast majority of the cohort.  Severe communication impairment was the most prevalent comorbidity (N=34/51, 67%) and was present regardless of the number of other domains impacted. Severe impairments in other domains were present in N=26 (51%) for mobility, N=7 (14%) for hand use, and N=22 (43%) for eating.   Several patients had multiple domains severely impacted. Of the 13 participants with only one severely affected domain, that domain was most often communication (11/13).  Hand use was the least likely to be impaired; however, when it was, all three other domains were also severely impaired.

Conclusions:

Our analyses suggest that there is a hierarchy of impairments in which communication may be severely affected in isolation from other basic functions.