Measurement of Tartrate-Resistant Acid Phosphatase and the Brain Isoenzyme of Creatine Kinase Accurately Diagnoses Type II Autosomal Dominant Osteopetrosis but Does Not Identify Gene Carriers

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Abstract
Autosomal dominant osteopetrosis type II (ADO2) is typically diagnosed from radiographs, which demonstrate the patho- gnomonic findings of osteosclerosis and endobone formation. Individuals with ADO2 also have elevated serum levels of tartrate-resistant acid phosphatase (TRAP) and the BB iso- enzyme of creatine kinase (CK-BB). In the current study, we tested the utility of these enzymes in making or refuting a diagnosis of ADO2. Furthermore, because ADO2 has incom- plete penetrance, we examined whether TRAP and CK-BB were helpful in identifying gene carriers. We studied eight families, measured serum levels of TRAP and CK-BB in 52 affected individuals and 12 obligate gene carriers, and com- pared their values with age-matched controls. Our results demonstrate that affected patients have significantly elevated levels of both TRAP and CK-BB. In contrast, gene carriers have values that are not different from controls. Furthermore, in our study population, TRAP and CK-BB have a high diag- nostic sensitivity and specificity, particularly in children. From this large study of ADO2 patients and carriers, we con- clude that: 1) TRAP and CK-BB are significantly elevated in patients with ADO2, 2) obligate carriers cannot be adequately identified by measurement of these analytes, and 3) TRAP and CK-BB are highly sensitive and specific diagnostic tests that can efficiently and effectively screen high-risk individuals who have not had previous radiographic assessment. (J Clin Endocrinol Metab 87: 2212-2217, 2002)

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