AKU in an ultra-rare autosomal recessive disease caused by the mutations of the Homogentisate 1,2- dioxygenase (HGD) gene which leads to a deficiency of the HGD enzyme (Ascher et al., 2019; La Du et al., 1958) producing accumulation of the unprocessed toxic catabolite homogentisic acid (HGA), especially in connective tissues. This evidence concerns the gene HGD and autosomal recessive disease.