NEMO and its causes

NEMO (nuclear factor-kappa B essential modulator) deficiency syndrome is a rare disorder and is often referred to simply as NEMO deficiency. It causes major
abnormalities of the immune system but can affect many parts of the body,
particularly the skin, hair, teeth and brain.

NEMO is a protein in white blood cells that signals infection. The protein is also
present in other cells, such as the skin and teeth, where it is important in making
the sweat glands, hair and normal-looking teeth. NEMO deficiency is one of a larger group of conditions known as primary immunodeficiencies. It is very variable in the symptoms it causes and how it progresses over time.

Another name for the condition is X-linked hypohydrotic ectodermal dysplasia
and immunodeficiency (XL-EDA-ID).

Causes of NEMO

NEMO deficiency is usually an inherited condition, passed on in families in the
same way that physical characteristics, such as eye colour, are passed from parent to child. It is caused by a mutation (change) in a child’s genetic make-up.

In boys with NEMO deficiency, one gene called IKBKG contains a spelling mistake (or mutation) that interferes with the normal function of the protein it makes, called NEMO. NEMO usually does an important job inside white blood cells as well as in the skin, where it is involved in developing teeth and hair.

As the IKBKG gene is located on the X chromosome, girls have a back-up copy so are very rarely affected. However, each time a female carrier has a baby boy, there is a 50 per cent chance her son will inherit the X chromosome bearing the mutated gene. This is called X-linked inheritance.

Sometimes new gene defects can occur ‘out of the blue’ in people with no history of the disorder in their family. If the genetic change occurs at the time of conception (in the eggs or sperm) it is called ‘sporadic’ and could be passed on to the next generation. If it occurs later in the development of the embryo, the gene mutation only affects blood cells and is called a ‘somatic’ variant. In this case, the genetic defect cannot be passed on to future generations.

Specialists in genetics and genetic counselling are on hand to talk through the
inheritance of NEMO with you if needed. More information about genetics is also
available in our separate leaflet 'Genetics of PID'.