A large family from Argentina with prekallikrein deficiency due to a compound heterozygosis (T insertion in intron 7 and Asp558Glu in exon 15): prekallikrein Cordoba

A Rare Cause of Isolated Prolonged Activated Partial Thromboplastin Time: An Overview of Prekallikrein Deficiency and the Contact System

Prekallikrein (PK) deficiency, also known as Fletcher factor deficiency, is a very rare disorder inherited as an autosomal recessive trait. It is usually identified incidentally in asymptomatic patients with a prolonged activated partial thromboplastin time (aPTT). In this article, we present the case of a 52-year-old woman, with no prior personal or family history of thrombotic or hemorrhagic disorders, who was noted to have substantial protracted aPTT through the routine coagulation assessment before a kidney biopsy. The patient had an uneventful biopsy course after receiving fresh frozen plasma (FFP). Laboratory investigations performed before the biopsy indicated normal activity for factors VIII, IX, XI, XII, and von Willebrand factor (vWF) as well as negative lupus anticoagulant (LA) screen. The plasma PK assay revealed low activity at 15% consistent with mild PK deficiency. The deficit of PK is characterized by a severely prolonged aPTT and normal prothrombin time (PT) in the absence of bleeding tendency. PK plays a role in the contact-activated coagulation pathway and the inflammatory response. Thus, other differential diagnoses of isolated prolonged aPTT include intrinsic pathway factor deficiencies and nonspecific inhibitors such as LA. We concluded that the initial evaluation of a prolonged aPTT with normal PT should appraise the measurement of contact activation factors and factor inhibitors. PK deficiency should be considered in asymptomatic patients with isolated aPTT prolongation, which corrects on incubation, with normal levels of the contact activation factors and factor inhibitors.

Severe plasma prekallikrein deficiency: Clinical characteristics, novel KLKB1 mutations, and estimated prevalence

BACKGROUND

Severe plasma prekallikrein (PK) deficiency is an autosomal-recessive defect characterized by isolated activated partial thromboplastin time prolongation. To date, no comprehensive methodologically firm analysis has investigated the diagnostic, clinical, and genetic characteristics of PK deficiency, and its prevalence remains unknown.

PATIENTS/METHODS

We described new families with PK deficiency, retrieved clinical and laboratory information of cases systematically searched in the (gray) literature, and collected blood of these cases for complementary analyses. The Genome Aggregation Database (gnomAD) and the population-based Gutenberg Health Study served to study the prevalence of mutations and relevant genetic variants.

RESULTS

We assembled a cohort of 111 cases from 89 families and performed new genetic analyses in eight families (three unpublished). We identified new KLKB1 mutations, excluded the pathogenicity of some of the previously described ones, and estimated a prevalence of severe PK deficiency of 1/155 668 overall and 1/4725 among Africans. One individual reported with PK deficiency had, in fact, congenital kininogen deficiency associated with decreased PK activity. One quarter of individuals had factor XII clotting activity below the reference range. Four major bleeding events were described in 96 individuals, of which 3 were provoked, for a prevalence of 4% and an annualized rate of 0.1%. The prevalence of cardiovascular events was 15% (6% <40 years; 21% 40-65 years; 33% >65 years) for an annualized rate of 0.4%.

CONCLUSIONS

We characterized the genetic background of severe PK deficiency, critically appraised mutations, and provided prevalence estimates. Our data on laboratory characteristics and clinical course of severe PK deficiency may have clinical implications.

Prekallikrein deficiency presenting as recurrent cerebrovascular accident: case report and review of the literature

We report the case of a woman with history of hypertension and hyperlipidemia presenting with recurrent episodes consistent clinically with cerebrovascular accidents (CVA), and MRI changes suggestive of ischemia versus vasculitis as their cause. No anatomical neurological, rheumatic, cardioembolic, or arteriosclerotic etiologies could be determined by extensive workup. Incidentally, the patient was found to have prolonged activated Partial Thromboplastin Time (aPTT) and a normal Prothrombin Time (PT); further testing revealed a prekallikrein deficiency. Since no other cause for the CVAs was established, and other prothrombotic states were ruled out, it is proposed that they are clinical manifestations derived from the prekallikrein deficiency, which in a patient with known cardiovascular risk factors could lead to thrombotic complications such as stroke.

Comparative incidence of thrombosis in reported cases of deficiencies of factors of the contact phase of blood coagulation

Thrombotic manifestations occurring in patients with coagulation defects have drawn considerable attention during the last decade. It concerned mainly patients with hemophilia, vW disease or FVII deficiency. Occasional reports involved also the deficiencies of the contact phase of blood coagulation, mainly FXII deficiency. The purpose of the present study was to evaluate the comparative incidence of thrombosis in all reported patients with FXII, Prekallikrein and Kininogens deficiencies. Out of the reported 341 cases with these conditions that could be tracked there were 43 cases with thrombosis. More specifically, there were 32 patients with FXII deficiency who also had a thrombotic event (16 arterial and 16 venous). As far as Prekallikrein deficiency is concerned, there were nine cases with thrombosis (five arterial and four venous). Finally, two patients with Total or High molecular weight Kininogen deficiencies had also a thrombotic manifestation (one arterial and one venous). The thrombotic manifestations were M.I. 11 cases; ischemic stroke 9 cases; peripheral arteries 3 cases; deep vein thrombosis with or without pulmonary embolism 17 cases; thrombosis in other veins 3 cases. Congenital or acquired associated prothrombotic risk factors were present in 33 out of 36 cases. In three cases the existence of associated risk factors was excluded whereas in the remaining seven patients no mention is made in this regard. This study clearly indicates that the severe in vitro coagulation defect seen in these conditions does not protect from thrombosis.