Pediatric Medicine

You don't look sickle

Study reveals circulatory abnormalities in apparently
normal sickle beta-thalassemia sufferers

By henry Peters

Twelve-year-old Maria Chronopoulos has a common variety of sickle cell disease, but, until recently, she's shown no signs of neurological abnormality. Then Maria had a stroke. Recent research may mark the first step towards early recognition of these events so in the future they won't come as such a shock. According to a study published May 3 in the on-line edition of the Annals of Neurology, 'silent' strokes or unseen circulatory system abnormalities may put children and teens with sickle beta-thalassemia at risk for overt strokes.

Sickle beta-thalassemia is a condition that arises when a child inherits one gene for sickle cell disease and one gene for thalassemia. Thalassemia, also known as Cooley's anemia, is the commonest inherited single-gene disorder in the world. Thalassemia is mostly found in people of Mediterranean ancestry, among whom the gene took hold because a single copy is beneficial � it helps protect against malaria. Thalassemia can be apparently asymptomatic or can cause severe birth defects, depending on the type and number of genetic mutations.

As with thalassemia, a single copy of the sickle cell anemia gene offers protection against malaria. Inheriting sickle cell genes from both parents, however, brings clinical disease. Take a little from column A and a little from column B and you get sickle beta-thalassemia, whose symptoms resemble those of sickle cell anemia, but which, like the symptoms of thalassemia, show a great gradation of severity.

Stroke is a recognized consequence of sickle cell disease,but patients with S-beta-thalassemia generally don't show any obvious indications of stroke, nor any drop in brain power that might hint at silent strokes � until it's too late.

Dr Dimitrios Zafeiriou, of the Aristotle University of Thessaloniki, Greece, and his colleagues carried out wide-ranging tests, including magnetic resonance imaging (MRI), on a group of 21 children and teens with S-beta-thalassemia in order to check for brain abnormalities. Magnetic resonance angiography (MRA) and transcranial Doppler (TCD) testing were also used to assess blood flow to the brain. Finally, neuropsychological tests uncovered any loss of brain power.

Despite showing no significant deficits on the neuropsychological testing, and having an average IQ of 98, MRI evidence revealed that more than a third of the patients had had previous silent strokes. Similarly, MCA and/or TCD testing showed that nearly a third of the patients, including many who hadn't had silent strokes, had abnormal blood flow to the brain "The next step will be to follow these patients in order to see if they will experience clinically overt stroke," said Dr Zafeiriou.

In the meantime, the authors call for all children with sickle beta-thalassemia to be "routinely screened with MRI and tests of brain blood flow in order to detect abnormalities not easily seen in clinical examination."