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MICROVILLOUS ATROPHY

Microvillous Atrophy (MVA) is an extremely rare genetic intestinal disorder, in which the bowel is unable to absorb any nutrients from food.  It is a catastrophic condition, which is both difficult to diagnose and complicated to manage.  Patients with MVA are unable to eat normally and are therefore totally dependent on being fed intravenously with TPN (Total Parenteral Nutrition). However, over time the use of TPN can cause damage to the liver, and the central line (known as a Hickman Line) through which the TPN is administered is prone to infection, often leading to sepsis. Consequently, the long-term outlook for children being treated in this way is poor.

daniel's hickman line
TPN
Daniel's Hickman Line
Daniel's TPN and fluids

There is currently no cure for MVA and the only alternative to TPN is intestinal transplantation. This can be performed either as an isolated small bowel, or a combined liver-bowel transplant if significant liver disease exists.

MVA is characterised by chronic diarrhoea, which in the majority of cases starts within the first week of life, usually within the first few days. The diarrhoea is immediately life threatening and can become so severe that a child can lose up to 30% of its body weight and become extremely dehydrated.(1) This type of MVA is referred to as congenital MVA.

daniel being weighed

In about 20% of cases, the onset of diarrhoea occurs later, usually within the second month of life.  This is known as late-onset MVA and is usually less severe.

MVA was first described in 1978 by an Australian doctor, (2) and by 1987 more than 30 cases had been identified worldwide. (3) More recently it has been estimated that there have been no more than 200 cases in Europe.  Published cases of MVA suggest a female to male ratio of 2:1.

In August 2008 it was discovered that it is the mutation of the MY05B gene that causes Microvillous Atrophy (4). The condition appears to be inherited on an auto recessive basis - i.e. where both parents are carriers of the defective gene.  Any child born to parents who both carry the gene, has a 1 in 4 chance of being born with MVA, a 50% chance of being a carrier and a 1:4 chance of not being affected and not being a carrier.

The diagnosis of MVA can be confirmed by an electron microscope.  The following images of the small bowel are taken from a patient with MVA.

MVA under an electron microscope

Disclaimer: please note that this article has been written to provide a general outline of MVA.  It is not intended to replace or substitute the care and expert advice of a qualified physician and you should not rely on this information to determine diagnosis, prognosis or treatment. Advances in medical technology may render information contained in this article outdated, invalid or subject to debate.

Acknowledgements

Our grateful thanks to Dr Neil Shah, Consultant Paediatric Gastroenterologist at Great Ormond Street Hospital, for providing the electron microscope images and much of the medical information on which this article was based.

References

1) Ruemmele FM, Schmitz J, Goulet O. Review: Microvillous inclusion disease (microvillous atrophy). Orphanet Journal of Rare Diseases 2006, 1:22 (26 June 2006)

2) Davidson GP, Cutz E, Hamilton JR, Gall DG. Familial enteropathy: A syndrome of protracted diarrhea from birth, failure to thrive, and hypoplastic villus atrophy. Gastroenterology 1978;75:783-90.

3) Guandalini S, MD, Nocerino, A, MD, PhD, Congenital microvillous atrophy. Emedicine, 18 May 2006

4) Thomas Müller, Michael W Hess, Natalia Schiefermeier, Kristian Pfaller, Hannes L Ebner, Peter Heinz-Erian, Hannes Ponstingl, Joachim Partsch, Barbara Röllinghoff, Henrik Köhler, Thomas Berger, Henning Lenhartz, Barbara Schlenck, Roderick J Houwen, Christopher J Taylor, Heinz Zoller, Silvia Lechner, Olivier Goulet, Gerd Utermann, Frank M Ruemmele, Lukas A Huber& Andreas R Janecke: MYO5B mutations cause microvillus inclusion disease and disrupt epithelial cell polarity. Nature Genetics, 24 August 2008