Myeloproliferative Disorders

This is overproliferation of blood cells and has a tendency to transform in to acute lekaemia. These conditions tend to affect those in middle or old age.

Polycythaemia

This is overproliferation of red blood cells.

Classification:

Apparent (i.e. not really raised)

Diuretics (decreased blood volume), obesity, hypertensino, smoking

Primary (polycythaemia rubra vera)

Raised RBC, WBC and platelets, bright red face.

Secondary

Hypoxaemic (compensatory): eg chronic lung disease, cyanotic congenital heart diseaes

Renal: eg hypernephroma, polycystic ovarian syndrome, renal cell tumour (causing a raised epo level)

Miscellaneous eg fibroids

Clnical features include facial plethora, headache, mental clouding and pruritus. The condition is associated with hypertension, splenomegaly, gout (hyperuricaemia) and bleeding. Occlusive vascular disease, for example stroke, may develop.

Investigations include:

1. Differentiate from apparent: measure red cell mass, plasma volume using radionucleotide labelling of RBCs and albumin
2. Serum epo: decreased in primary (negative feedback)
3. Jak 2 mutation (mutation in epo rec allows epo independent proliferation)
4. Bone marrow biopsy: hyperplasia, fibrosis, Fe deficiency, cytogenetic abns
5. Spleen USS

Treatment is repeated venesection to maintain a normal PCV. Hydroxyurea if thrombocytosis is present. Low dose aspirin to reduce the risk of vascular events is useful. IV radioactive phosphorus may be given to reduce bone marrow proliferation of red blood cells however this treatment is restricted to the elderly because it there is an increased risk of leukaemia

Essential Thrombocythaemia

This is excess platelets in the blood. Presentation is with microvascular occlusive events, such as erythromelalgia (burning pain in extremities), or major occlusive events such as stroke. Livedo reticularis is a red marbling rash which is associated with the condition.

Investigations:

1. Blood film: increased platelets
2. Bone marrow: increased megakaryocytes

Treatment is with low dose aspirin to reduce occlusive events. Hydroxyurea reduces the number of platelets in the blood.

Myelofibrosis

In this condition the bone marrow is replaced by fibrous tissue. and thus production of red and white cells is reduced. It occurs in middle aged/elderly people usually. Patients may present with massive splenomegaly, symptoms of anaemia, weight loss, bleeding and cachexia. Investigations reveal:

1. Anaemia
2. "Marble bone" (increased density) on XR
3. Blood film: leukoerythroblastic picture (leukoblasts, myelocytes), tear drop cells
4. Bone marrow: abnormal megakaryocytes, increased fibrous tissue