TPI1 and hyperinsulinemic hypoglycemia, familial, 4: In the situation of an RBC enzymopathy, the RBC morphology is usually reported to not be specific, but some abnormalities, although unremarkable, may still be suggestive of a particular deficiency such as prominent basophilic stippling in pyrimidine-5ʹ-nucleotidase deficiency or the presence of echinocytes in triose phosphate isomerase or PK deficiency [15].