Alpha-thalassemia in Papua New Guinea.

A study of the distribution of alpha-thalassemia in Papua New Guinea (PNG) was carried out by DNA analysis. A total of 664 DNA samples were screened for alpha-thalassemia 2 and alpha-thalassemia 1 caused respectively by either deletion of one or both of the duplicated alpha-globin genes. alpha-Thalassemia 2 was detected in high frequencies in coastal and lowland regions where malaria has been holo- to hyperendemic but in low frequencies in non-malarious highland regions. The highest frequency was observed in the north coast of PNG. The distribution of alpha-thalassemia 2 seems to be in accordance with other conditions such as ovalocytosis and G6PD deficiency which are also prevalent in this population, suggesting that they may interact in protection against malaria. However, it appears to be negatively correlated with beta-thalassemia and alpha-thalassemia 1, the latter being extremely rare in this population. Analysis of the types and subtypes of the single alpha-globin gene deletion revealed a predominance of the -alpha 4.2 type in general, except in some regions in the south where the -alpha 3.7 type is prevalent. The -alpha 3.7 I subtype is the common form of the -alpha 3.7 deletion in the PNG mainland. The -alpha 3.7 III subtype, previously reported to be unique in Melanesians and Polynesians, was detected in an offshore island of PNG. However, this subtype is very rare in Melanesians from the PNG mainland.