Lactate dehydrogenase-6: a case with acute onset and resolution.

We recently notedthe presence of a sixth lactate dehydrogenase (EC 1.1.1.27) isoenzyme (LDH-6) in a previously well patient with chest and abdominal trauma. The patient, a 60year-old woman with hypertension but without other significant medical history, was involved in a motor vehicle accident with clavicular and rib fractures and a ruptured spleen. Her systolic pressure dropped into the 80’s (mmHg) before fluid resuscitation. At surgery, the spleen was actively bleeding, but the liver appeared undamaged. Her postoperative coursewas uneventful without evidence of cardiac or pulmonary contusion and she was discharged in good condition on the eighth day of hospitalization. Total LDH 2.5 h after admission was 1370 U/L (reference range 112-217 U/L) with 1.1% LDH-6 (migrating anodic to LDH-5); the proportions of LDH-4 and LDH-5 were also above normal. Simultaneously, creatine kinase (EC 2.7.3.2; CK) was increased (732 U/L; reference range 20-170 U/L), with 4.9% CK-MB and 3.9% CK-BB. A repeated assay of enzymes 35 h after admission showed normalization of LDH isoenzyme fractions with disappearance of the LDH-6. The CK-BB fraction disappeared and the CK-MB decreased. The existence and significance of LDH-6 have been reported and discussed since 1980. In most cases, the presence of suchan enzyme seems to relate to serious generalized or hepatic circulatory disturbances and signifies a poor prognosis. Most cases involve elderly patients with severe chronic cardiovascular abnormalities and profound shock. Previous cases with LDH-6 have also been associated with an increase in CK and have had MB and MM fractions. The presentcase suggeststhat even a very acute, temporary hypotensive episode or possibly direct trauma to the liver in a healthy patient may be associated with an LDH-6. However, the condition may be rapidly reversible and not necessarily associated with a poor prognosis.