A not so crystal-clear case.

A physician from an outside hospital called our laboratory for help regarding interpretation of cerebrospinal fluid (CSF) results. She was confused by a report from her laboratory that reported the presence of “calcium oxalate crystals 3 ” upon microscopy examination of a CSF sample (Figure 1). The CSF findings were as follows: protein concentration, 0.9 g/L, (reference interval, 0.15– 0.35 g/L); chloride, 106 mmol/L (reference interval, 120 –130 mmol/L); and glucose, 65 mg/dL (3.5 mmol/L) [reference interval, 40 –70 mg/dL (2.2–3.9 mmol/L)]. Clinically, the patient presented with features suggestive of acute infective meningitis. There was no current or previous history of toxin ingestion, suicide attempts, arthritis, or renal calculi.