The prevalence of pyruvate kinase (PK) deficiency clinical diagnoses in Western countries was estimated to be in the range of 3.2 to 8.5 cases per million people, in a recent analysis published in the European Journal of Haematology. The estimated rate was much higher when including undiagnosed cases.

The prevalence of PK deficiency has been unclear for a variety of reasons, such as the rarity of the condition and its varied presentation that can mimic other disorders affecting red blood cells.

The investigators conducted a literature-based review of studies involving PK deficiency. Of the 34 deeply analyzed studies, 4 were deemed appropriate for estimating the prevalence of PK deficiency, although methodologies differed between studies.

One study with known population size estimated a rate of PK deficiency cases of 3.2 per million from a population of 3.1 million people in the United Kingdom. Another with a given population size found an estimate of 8.5 per million from a population of 6.5 million people in Quebec, Canada. A third study involving screenings of newborns with jaundice gave an estimated prevalence of PK deficiency of 6.5 cases per million births in the United States.

The fourth study gave an estimate of the combination of diagnosed and undiagnosed cases of PK deficiency of 51 per million, but with a standard error of 32.5 per million, indicating considerable uncertainty. This estimate was based on analyses of allele frequencies involving mutations in the PKLR gene, which encodes PK. PKLR mutations can be associated with varying degrees of PK function and be a source of clinical heterogeneity.

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“Future studies are needed to understand the clinical significance of various mutant alleles, which may inform more accurate, clinically-relevant PK deficiency prevalence estimates, identify the degree of and reasons for underdiagnosis, and elucidate PK deficiency heterogeneity between populations. Some of this additional research is currently being conducted through existing patient registries,” the authors concluded.

Disclosure: This study was supported by Agios Pharmaceuticals. Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Secrest MH, Storm M, Carrington C, et al. Prevalence of pyruvate kinase deficiency: a systematic literature review [published online April 12, 2020]. Eur J Haematol. doi: 10.1111/ejh.13424