acid phosphatase
Summary
Acid phosphatase is an enzyme optimally active at acidic pH, historically used as a serum marker for prostate cancer before being replaced by PSA. It is also notably elevated in Gaucher disease and can be used forensically to detect seminal fluid in sexual assault evidence.
Detail
Acid phosphatase (ACP) is a lysosomal enzyme found in prostate tissue, bone (osteoclasts), platelets, erythrocytes, and macrophages. Prostatic acid phosphatase (PAP) was historically used as a tumor marker for metastatic prostate cancer, particularly bone metastases, but has largely been superseded by prostate-specific antigen (PSA) due to better sensitivity and specificity. Tartrate-resistant acid phosphatase (TRAP) is a specific isoform used as a diagnostic marker for hairy cell leukemia (TRAP-positive) and is also elevated in Gaucher disease, a lysosomal storage disorder caused by glucocerebrosidase deficiency leading to accumulation of glucocerebroside in macrophages (Gaucher cells). Osteoclasts also express high levels of acid phosphatase, making it useful as a marker of bone resorption activity in conditions like Paget disease or osteoporosis research. In forensic medicine, acid phosphatase activity in vaginal or other bodily fluid swabs is used as a presumptive test for the presence of seminal fluid in sexual assault cases, since semen contains very high concentrations of prostatic acid phosphatase. Elevated serum acid phosphatase can also be seen in other conditions such as Niemann-Pick disease, multiple myeloma, and certain bone diseases, though these are less clinically emphasized on standard exams.
Sources
- First Aid for the USMLE Step 1
- Robbins and Cotran Pathologic Basis of Disease
- Goljan Rapid Review Pathology
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