Spleen sizing by ultrasound in polycythaemia and thrombocythaemia: comparison with SPECT

Detection of non-palpable early splenic enlargement may aid diagnosis of primary polycythaemia (PP) and primary thrombocythaemia (PT). In this study linear spleen sizing by ultrasound has been compared with spleen volume estimation by single photon emission computerized tomography (SPECT) in 26 patients. Spleen length by ultrasound correlated well with SPECT volume estimation.
Ultrasound spleen length was also measured in 60 normal control subjects where the upper limit of the 95% reference range was 11.6 cm. Changes in spleen length with both age and body weight were substantial and overshadowed the imperfect reproducibility of this method. Therefore, interpretation of an individual's measured spleen length should be in relation to that predicted for adults of the same age and weight, particularly at the extremes of the younger, heavier patients and also the older, lighter patients.
Ultrasound spleen lengths of different patient groups (21 PP, 26 PT, 17 idiopathic erythrocytosis, 12 secondary polycythaemia, nine apparent polycythaemia) were compared both using the measured overall reference range and the differences from the values predicted for their age and weight. The comparison showed that almost all patients with PP whose spleens were not palpable had spleen lengths greater than the upper limit for the normal control group, but separation from the other patient groups was incomplete.
Detection of non-palpable splenomegaly by ultrasound length should remain a 'minor' criterion amongst the 'proposed modified diagnostic criteria' of PP.     

Normal outcome of pregnancy in chronic myeloid leukemia treated with interferon-alpha in 1st trimester: report of 3 cases and review of the literature

Three patients with chronic myeloid leukemia (CML) in chronic phase received interferon-alpha during pregnancy, starting from the 1st trimester. No maternal complications were reported. The 3 patients delivered normal looking babies apart from one baby who was found to have transient mild thrombocytopenia. Subsequently these children were followed for 30, 12, and 4 months and all had normal growth and development.     

Thromboxane-dependent platelet activation in vivo precedes arterial thrombosis in thrombocythaemia: a rationale for the use of low-dose aspirin as an antithrombotic agent

The clinical course of patients with polycythaemia vera (PV) and essential thrombocythaemia (ET) is frequently complicated by arterial thrombotic events. The pathogenesis is not clearly understood but attributed to abnormalities in platelet function. An increase in platelet thromboxane formation has been described in the majority of asymptomatic patients with thrombocythaemia, probably reflecting spontaneous platelet activation in vivo. In the present study we prospectively investigated whether an increase in platelet thromboxane formation actually precedes arterial microvascular thrombosis. In addition, we studied the effect of selective inhibition of platelet thromboxane formation on clinical outcome by reinstitution of low-dose aspirin (50 mg/ d). Six ET patients and one PV patient participated in this study. Within 10 d after withdrawal of aspirin, three patients developed arterial microvascular thrombosis of extremities (erythromelalgia), which was preceded by a 3-30-fold increase in urinary thromboxane excretion as compared with patients who remained asymptomatic. The increased urinary thromboxane excretion and clinical signs could be inhibited by a platelet-specific aspirin regimen of 50 mg/d without affecting vascular cyclooxygenase, indicating that platelets were the main source of the increased thromboxane generation. These data suggest that in symptomatic patients an enhanced formation of thromboxane by platelets, reflecting platelet activation in vivo, precedes the development of arterial microvascular thrombosis. These data provide a rationale for using low-dose aspirin as an antithrombotic agent in thrombocythaemia.     

The JAK2V617F mutation and thrombosis

Since the discovery of the JAK2^V617F mutation, the clinical and pathological consequences of this acquired defect have been extensively investigated to determine whether its presence characterises a distinct subgroup of myeloproliferative disorders (MPD). MPD management remains highly dependent on the patient’s thrombotic risk. Whether the presence of the JAK2^V617F mutation modifies the thrombotic risk is currently contentious, although there is increasing clinical evidence to suggest that the mutation may be variably associated with thrombosis. These observations are further supported by laboratory parameters which suggest that the JAK2^V617F mutation may confer increased activation of leucocytes and platelets in MPD. The role of screening for the JAK2^V617F mutation in patients presenting with thrombosis without overt MPD is unclear, but appears justified in cases of idiopathic splanchnic vein thrombosis.