Worldwide Distribution of PK Deficiency: the Defect Seems Mainly Concentrated in West African Countries and the United States.

To the editor.

PK deficiency was first reported in 1965 in the USA in a family composed of a Caucasian woman and an African American (AA). The woman was an unrecognized heterozygote for PK deficiency, whereas the AA man was either an unrecognized heterozygote or a homozygote for the same defect.1

Two of their children were homozygotes for the defect.2

After these publications, several cases appeared.3 Sollo and Saleem were the first ones in 1985 who, based on a table in which they gathered most of the papers published on the subject, suggested that the defect was frequent among AA.4

Subsequently, studies confirmed this assumption. The history of African Americans who had been brought “forcefully” to the US as “slaves” indicated that the defect should be frequent in the West African States where they came from.5,6

Until now, PK defect appeared rare in these countries.7 Recently, in a preliminary study, it has been demonstrated that the defect is present in 1.27% of 300 Nigerians.8 The defect was found to be due to a Ser151Pro fs mutation. Interestingly, the only AA investigated was found to have the same mutation.9 This is the first genetic link established between African-Americans and the African population.

The link had been suspected on historical consideration5,6 but not genetically.

It remains to be proven if this is the only mutation present among AA or, more likely, other mutations will be discovered.

This mutation is different from the mutations found in Europeans, Asians, and Argentinians.3 It is interesting to know that the same mutation was also found in a patient from Oman and Somalia (East African States).8 This could indicate that the mutation may be present even in the Central African States.

These findings, if confirmed and extended, could cast some light on the high frequency of Cardiovascular Disorders (CVD) seen among AA.10–12 It would also allow the possibility to differentiate the effects of a genetic abnormality from diet and environment, which have been and still are quite apart between the USA and African countries.