Persistently elevated serum concentrations of human chorionic gonadotropin (hCG).

OBJECTIVES: We describe a woman with constantly elevated hCG levels in serum. Since assay interference, pregnancy or cancer did not explain the elevated levels, we measured the concentrations of hCG, its ß subunit (hCGß) and its core fragment (hCGßcf) in serum and urine using specific assays, to understand the nature of the elevated hCG levels. METHODS: We used 3 assays for total hCG (these assays also recognize hCGß and to various degrees hCGßcf), 3 for intact hCG heterodimer, 3 for free hCGß and one for hCGßcf. RESULTS: With an hCG assay detecting total hCG the serum concentrations were in the range of 150-260 IU/L for the whole study period of almost 5 years, except for a peak of 1,200 IU/L, coinciding with a spontaneous abortion. Quantitation of different forms of hCG with specific immunoassays showed that the immunoreactivity in serum consisted of hCGß. Urine contained hCGß and hCGßcf. CONCLUSIONS: The laboratory findings are in keeping with familial hCG syndrome. However, so far the condition remains to be determined in any family members. Elevated hCG levels without any explanation are problematic as they cause suspicion of cancer or ectopic pregnancy and may lead to harmful therapy. Specific assays, as used here, will aid in diagnosis of such cases.

Identification of a new mutation in the human xanthine dehydrogenase responsible for xanthinuria type I.

Objectives: Hereditary xanthinuria is a rare, autosomal and recessive disorder characterized by severe hypouricemia and increased xanthine excretion, caused by a deficiency of xanthine dehydrogenase/oxidase (XDH/XO, EC: 1.17.1.4/1.17.3.2) in type I, or by a deficiency of XDH/XO and aldehyde oxidase (AOX, EC: 1.2.3.1) in type II. Methods: We describe a novel point mutation in the XDH gene in homozygosis found in a patient with very low serum and urine levels of uric acid, together with xanthinuria. He was asymptomatic but renal calculi were discovered during imaging. Results: Additional cases were found in his family and dietary recommendations were made in order to prevent further complications. Conclusions: Hereditary xanthinuria is an underdiagnosed pathology, often found in a routine analysis that shows hypouricemia. It is important for Laboratory Medicine to acknowledge how to guide clinicians in the diagnosis.