|Medical Ophthalmology: Case eleven|
This is the blood film of a young man who suffers from poor night vision. In addition, he has a learning difficulty and problem with balance.a. What does the blood film show?Acanthocytosis. These are spiky red blood cells caused by membrane abnormalities.
b. What is the diagnosis?Abetalipoproteinaemia (Bassen-Kornzweig syndrome)
c. Why does he have problem with night vision and what other
ocular signs may be present?The poor night vision is caused by pigmentary retinopathy which is similar in appearance to retinitis pigmentosa.
Other possible ocular signs include:
- ocular motor abnormalities such as
- slow saccade movement
- internuclear ophthalmoplegia
- external ophthalmoplegia
- ptosis ; which typically occurs in the abducting eye
d. What is the pathophysiology of this condition?It is an autosomal recessive disorder in which there is impaired intestinal absorption of lipids and lipid-soluble vitamins (A, E and K).
In the plasma, there is an absence of beta (low density) lipoprotein and hence the name abetalipoproteinaemia.
The vitamin E deficiency causes cerebellar degeneration and demyelination of neurones giving rise to neurological signs which include ataxia, areflexia and poor vibratory sensation. The retinopathy is thought to be partly caused by vitamin A deficiency.
e. How can this condition be treated?If the condition were diagnosed early, the neurological and retinal problems may be prevented with large doses of vitamin A and E.