Heterozygous Alpl+/- mice survive normally and exhibit a 50% decrease in TNSALP activity and expression.46 Previous studies have revealed that Alpl+/- mice do not exhibit significant radiographic evidence of skeletal disease.46 However, we observed that the 4-month-old Alpl+/- mice exhibited not only severe bone mass loss but also a marked marrow fat gain. The gene discussed is ALPL; the disease is bone disorder.