Читать книгу Haematology - Barbara J. Bain, Irene Roberts - Страница 18

9 Acanthocytic red cell disorders

A 50‐year‐old man with a progressive myopathy and cardiomyopathy was referred to a neurologist because of early cognitive decline and tic‐like involuntary movements. His full blood count was normal but a blood film was requested. This showed prominent acanthocytes; these are dense cells with prominent cytoplasmic projections (spicules), which are irregular in length and shape (acanthus is Greek for ‘thorny’) (left images ×100 objective). Routine renal and liver biochemistry and serum lipids were normal. A diagnosis of McLeod syndrome was considered and confirmed when a mutation in the XK gene at Xp21.1 was identified. McLeod syndrome is an X‐linked multisystem disorder, being one of a number of the rare neuroacanthocytic disorders. The condition is characterised by acanthocytosis, mild compensated haemolysis, weak expression of Kell blood group antigens, myopathy, cardiomyopathy and progressive neurological decline with cognitive impairment, involuntary movements, seizures and peripheral neuropathy. Peripheral blood morphology may provide a useful pointer to the diagnosis, as in this case.

A second patient, a 15‐year‐old boy was referred to ophthalmology with a progressive decline in visual acuity. He was found to have retinitis pigmentosa. He had a very low total cholesterol level, and low‐density and very low‐density lipoproteins (LDL and VLDL) were absent. His full blood count was normal but the requested blood film showed acanthocytes (centre images ×100). A diagnosis of abetalipoproteinaemia was considered and confirmed when biallelic mutation of the microsomal triglyceride transfer protein gene (MTTP) was identified. Abetalipoproteinaemia is a rare autosomal recessively inherited condition of lipid metabolism in which LDL and VLDL are severely reduced. The condition is characterised by fat malabsorption, spinocerebellar degeneration, acanthocytosis and retinitis pigmentosa. The MTTP protein influences intracellular lipid transport in the small bowel and liver. Symptoms usually first appear in infants and children, and when the condition is identified disease progression can be slowed using dietary vitamin E and medium chain fatty acid supplementation.

A third patient, a 32‐year‐old man with malnutrition from severe exocrine pancreatic insufficiency of unknown aetiology was hospitalised with a respiratory infection. He was poorly compliant with pancreatic enzyme supplements and appeared ill, grossly malnourished and wasted. His full blood count showed Hb 109 g/l, MCV 86.5 fl, MCH 26.3 pg, WBC 6.2 × 10⁹/l and platelets 218 × 10⁹/l. Serum ferritin was low at 9 μg/l and a blood film was requested. This showed significant hypochromia, consistent with iron deficiency, but also marked acanthocytosis with some of these cells appearing very dense (right images ×100). His lipid profile was abnormal, showing total cholesterol 2.2 mmol/l (optimal <5.2), triglycerides 0.8 mmol/l (NR 0.2–2.3), high‐density lipoprotein 0.6 mmol/l (optimal >1), LDL 1.2 mmol/l (optimal <2.59) and VLDL 0.4 mmol/l (NR 0.1–1.7). Serum apolipoprotein B levels were 0.6 g/l (NR 0.6–1.3) and screening for mutation in MTTP was negative. A diagnosis of acquired acanthocytosis, with iron deficiency secondary to severe lipid malabsorption from pancreatic exocrine failure was made.

MCQ

1 Acanthocytes in a blood film can be the result of:Anorexia nervosaLiver failureSplenectomyStorage artefactTransfusion of blood at the end of its shelf lifeFor answers and discussion, see page 206.