Our finding that peripheral blood leukocyte counts can be reduced by activating cGMP signaling suggests that leukocyte count could serve as a good surrogate marker for evaluating the sGC-cGMP pathway in SCD patients who receive a phosphodiesterase 5 inhibitor or other sGC-cGMP pathway activator [45]. This evidence concerns the gene SGCB and Schnyder corneal dystrophy.