The Activated Protein C Resistance Phenotype of the Antiphospholipid Syndrome May Follow a Relapsing Course

Abstract

Activated protein C resistance, the most frequent thrombophilic condition may be inherited or acquired; the an tiphospholipid syndrome, either primary or secondary is one of the causes of the acquired form. The case of a patient with a primary form of antiphospholipid syndrome in whom the acti vated protein C resistance phenotype was assessed in four in stances during a 3-year period is presented. In two instances the abnormal phenotype of the activated protein C resistance was present, whereas in the other two it was absent. The factor V gene (G→A, 1691) leading to the (R 506 Q) factor V mutation, typical of most inherited forms of the activated protein C re sistance, was not found. The relapsing behavior of this phe nomenon has not been previously shown. The changing pattern of this abnormality could explain discordant previous reports about the prevalence of the activated protein C resistance phe notype in patients with primary or secondary forms of the an tiphospholipid syndrome.