This very rare phenotype is generally present in about 0.0004% (about 4 per million) of the human population, though in some places such as Mumbai (formerly Bombay) locals can have occurrences in as much as 0.01% (1 in 10,000) of inhabitants.
Fenotipe ini sangat sangat langka dan hanya ada pada 0,0004% populasi manusia (sekitar 4 dari satu juta), walaupun di beberapa tempat (seperti Mumbai) persentasenya dapat naik hingga mencapai 0,01% (1 dari 10.000).