C1NH Deficiency: Causes, Symptoms, Diagnosis and Treatment

C1NH also known as C1 esterase inhibitor deficiency is a hereditary disorder which is characterized by frequent episodes of edema in hands, legs, gastrointestinal lining and airways. Unlike edema due to allergic reaction swelling in C1NH deficiency is not accompanied with itching. Edema or swelling in C1NH occurs because of deficiency of certain protein called C1 esterase inhibitor also known as complement.

Its function is to facilitate or regulate the flow of fluid in and out of the capillaries and body cells. Because of deficiency of this particular protein, the flow of fluid and blood is blocked which results in rapid swelling in certain areas. The condition is also referred as hereditary angioedema.


Hereditary angioedema is a rare genetic condition which may affect males and females equally. The symptoms usually start during the childhood. According to an estimate, there are 50000 to 150000 individuals affected with this condition. Hereditary angioedema is further divided into type 1 and type 2 angioedema. It occurs due to genetic defect in mother as well as father.

It is an autosomal dominant genetic disorder. One copy of defective gene from any one parent may be enough to produce this condition. It may sometimes also develop due to spontaneous gene mutation without any hereditary trait. The symptoms develop because of deficiency in a protein C1 esterase inhibitor. Type 1 is more common than type 2.

Signs and Symptoms:

The signs and symptoms of C1NH deficiency typically cause recurrent episodes of edema (swelling) in different parts of body. Usually swelling occurs in hands, legs, eyelids, lips, throat, airways, lining of intestine, genitals etc. Person suffering from this type of swelling have pain and hardness in the swollen area. But itching is missing. In case of edema due to allergy there is severe itching. This is a differentiating point between the two. Skin rash is absent. The symptoms may be mild or severe. They become worse with presence of certain triggers such as injury, surgery, dental procedure, viral fever, stress etc. The symptoms may vary according to the system involved. For example if gastrointestinal tract is involved, patient may complain of pain and cramps in abdomen, nausea and vomiting. Swelling in throat can lead to difficulty in swallowing food, difficulty in speaking, and sometimes difficulty in breathing in severe case.

Diagnosis and Treatment:

Diagnosis of C1NH deficiency is possible with clinical examination, detail medical history and blood test that will show low level of complement protein. In some cases genetic testing also provides sufficient clue for diagnosis of the condition.

Treatment focus is to stop swelling as soon as possible as it can be life threatening if it involves the airways and throat. In certain parts of world, C1 inhibitor concentrate derived from human blood is used and administered intravenously. Few physicians use fresh frozen plasma as it contains C1 inhibitor. Certain medications approved by FDA are also used to treat acute attacks. To prevent episodes of angioedema during surgery, dental procedures, a course of these medications is given to the patient for short period of time before the surgery of dental work. If acute attack causes edema and obstruction in the airway an opening is made surgically in the throat to make the way for air entry through a tube. This procedure is called tracheostomy.