PNP and Schnyder corneal dystrophy: In adult patients with SCD (n = 63), plasma PNP levels were markedly elevated compared to controls (n = 27; p < 0.001) and correlated positively with LDH (r = 0.6032, p < 0.0001) and negatively with haemoglobin (r = −0.4523, p = 0.0002).