Participants previously diagnosed with PK deficiency in Study AG348-C-008 (NCT03481738), will receive routine clinical care.

The PKDD is a 7-item measure of the core signs and symptoms of PK deficiency. The score range is 25 to 76, with higher scores indicating a higher disease burden.

The PKDIA is a 12-item measure of the impacts of PK deficiency on patients' HRQoL. The score range is 30 to 76, with higher scores indicating a higher disease burden.

WPAI:SHP is a 6-question participant-rated questionnaire to determine the amount of absenteeism, presenteeism, work productivity loss, and daily activity impairment attributable to PK deficiency for a period of 7 days prior to each visit. It yields 4 sub-scores: work time missed (absenteeism), impairment while working (presenteeism or reduced on-the-job effectiveness), overall work impairment (work productivity loss or absenteeism plus presenteeism) and activity impairment (daily activity impairment). These sub-scores are transformed to impairment percentages (range from 0 to 100), with higher numbers indicating greater impairment and less productivity.

FACT-An is composed of five subscales: Physical Well-Being [score range 0-28], Social/Family Well-Being [score range 0-28], Emotional Well-Being [score range 0-24], and Functional Well-Being [score range 0-28] and specific questions concerning anemia [score range 0-80]. The score at each item is summed. The sum is multiplied by the number of items in the subscale and then divided by the number of items answered. This produces the subscale score. The subscale scores are added to derive a total score [score range 0-188]. A higher score indicates better quality of life.