Absence of thymus

Introduction The absence of thymus is a clinical manifestation of congenital thymic hypoplasia. Congenital thymic hypoplasia is also known as DiGeorge syndrome or the third and fourth pairs of pharyngeal sac syndrome. It is a congenital immune deficiency caused by abnormalities of the pharyngeal sacs in the first to sixth stages of the embryo.

Cause

Cause of thymus deficiency

The cause of this disease is the congenital immune deficiency caused by abnormalities of the pharyngeal sacs in the first to sixth embryos. At the 6th to 10th week of the embryo, the thymus, parathyroid gland and part of the face, aortic arch and cardiac tuberculosis develop from the first to the sixth cell components of the pharyngeal sac. By the 12th week of pregnancy, the thymus migrated to the chest, which was previously caused by abnormal development of these embryonic tissues.

an examination

Related inspection

Chest CT examination of chest B blood routine chest radiograph

Absence of thymus

Laboratory examination

(1) Lymphocytes decrease in peripheral blood, especially T cells decrease, and the percentage of B cells increases.

(2) Cellular immune function has been reduced to varying degrees.

(3) The humoral immune function is variable, and serum immunoglobulin is often not low.

(4) The blood calcium content is lowered.

(5) The level of parathyroid hormone is lowered.

2. X-ray examination: shows that the thymus is reduced or absent.

3. Lymph node biopsy: shows lymphocyte deficiency in the paracortical area.

Differential diagnosis

Differential diagnosis of thymus deficiency:

The thymus is highly atrophied: there is an organ called the thymus that weighs only 10 grams on the upper edge of the human sternum. The T cells produced by the bone marrow only enter the thymus with the blood and are affected by thymus hormones. Finally, about 5% of the thymocytes develop into mature T lymphocytes with immune function. Chest CT scan is an important means of diagnosing thymic carcinoid tumors. It can clearly show the shape of the tumor itself and the infiltration of adjacent organs. In particular, enhanced CT can clearly show the condition of invasion of the superior vena cava, and provide important reference value for the choice of surgical plan. When clinical manifestations of ectopic ACTH syndrome appear, but because of the small chest X-ray examination can not be clearly diagnosed, CT scans can often find smaller thymoid carcinoid lesions, so that the diagnosis is clear.

The sternocleidomastoid and trapezius tendon are atrophied: the injury of the spinal nerve branch of one side of the accessory nerve or the damage of the spinal cord, the ipsilateral sternocleidomastoid and the trapezius tendon, and atrophy, due to the contralateral side The sternocleidomastoid is dominant, so when it is calm, the chin is turned to the affected side, and when it is forced, it is weak to the contralateral side, the affected side is drooping, the shoulder cannot be shrug, the shoulder blade is skewed, and the muscles it swells due to the shoulder blade. Displacement causes the brachial plexus to undergo chronic traction, which limits the lifting and abduction of the upper limb of the affected side. In the late stage, due to scar stimulation, a hernia contraction (rose neck) deformity can occur. When bilateral damage occurs, the patient's head and neck are reclined and front. Paralysis, paracranial fractures or gunshot wounds caused by accessory nerve injury, jugular vein hole lesions, occipital macropore lesions, cerebral cerebral horn angle lesions and subcranial lesions caused by paraneoplastic lesions and medullary nucleus often The posterior group of cranial nerves and other cranial nerve lesions appear at the same time, while in the brainstem nuclear paralysis, the damage of the cranial nerves is often more and bilateral.

Atrophy of the vocal cords: the vocal cord's own tissue and the muscles of the vocal cords are atrophied. Once the vocal cords are atrophied, the vocal cords are easy to close when we are vocalizing. So the patient can easily feel that the speech is very tired and the sound will be hoarse. This in turn leads to the inability of the patient to achieve a high and low level when working and singing.

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