Aplasia is a manifestation of a fetal malformation, which is expressed in the absence of any organ, its part or tissue sites. This pathology should be distinguished from hypoplasia, in which the organ can be in its infancy or reduced in size and devoid of a normal structure.
What causes the pathology
It should be noted that aplasia is a congenital disease that occurs as a result of exposure directly to the fetus or indirectly through the mother's body of physical, chemical and biological factors. They, acting on the gametes of parents or their ancestors, are able to cause chromosomal pathologies with the absence of any organ or tissue.
By the way, the undevelopment of one organ in an embryo is practically never isolated and leads, as a rule, to the death of another organ associated with it. For example, in the absence of an embryo of the ureter, aplasia of the secondary kidney occurs, etc.
And the deadline after which the described defects in the embryo can no longer develop is the first month of fetal life.
Features of the formation of pathology
In the human body there is no area in which aplasia cannot be observed. This pathological condition of one of the paired organs usually causes hypertrophy of the other (aplasia of one of the endocrine glands can cause hypertrophy of the others). Thus, there is a substitution, compensation for lost functions.
Often there is a lack of part of some organ, for example, aplasia of the corpus callosum or olfactory brain (this condition is called arinencephaly), etc. Aplasia of the tissue is most often observed on the skin of the scalp. At this place, a defect is found in the born baby, which usually does not exceed 5 cm across. But this condition is combined, as a rule, with aplasia of the tissue located deeper, for example, in cases with non-closure of the embryonic crevices (the so-called dysarphia).
Pathological development of bone tissue
As in the cases described above, aplasia of bones in the isolated form is extremely rare. So, with a similar pathology of the fibula, the patient shortens the limb, develops equinovarus deformation of the foot (its front edge is raised and the outer edge is lowered), the tibia is bent, and there are no calf and peroneal muscles.
In medicine, cases of aplasia of certain parts of the body are recorded , often this happens with human limbs. This may be the absence of one or more fingers, or the entire hand or foot. There are frequent options for the absence of a forearm, lower leg, shoulder, hip in the presence of a foot or hand.
Aplasia of the skull and brain
In case of focal aplasia of the bones of the skull, which in medicine is also called the “fenestrated skull”, through defects are formed in it, which have different sizes and shapes. But the periosteum (the fibrous membrane covering the bone tissue) and the skin remain in place of these defects. They are located most often in the parietal or frontal areas.
If the newborn does not have cranial bones, then aplasia of the brain is often observed with them (it is also called anencephaly). This pathology is 100% fatal. Moreover, 75% of children die in utero, and the rest live no more than 5 days after birth.
Although there is a known case of the birth in the USA in 1992 of a girl with a similar diagnosis, who lived 2 years and 174 days. The breathing and functioning of the internal organs in her body was carried out due to the preserved brain stem. But, nevertheless, the girl was periodically connected to the artificial respiration apparatus, as the resulting crises caused him to stop.
Aplasia of the uterus and vagina
Cases of underdevelopment or complete absence of the uterus, fallopian tubes and vagina are an infrequent pathology. Women who have it cannot get pregnant or bear a baby on their own.
A problem is usually found when puberty is reached . The girl is led to the doctor by complaints of the absence of menstruation and (in the absence of a vagina) the impossibility of sexual activity. At the same time, the patient most often maintains a normal physique and secondary sexual characteristics are well developed.
If the patient has a partial aplasia of the vagina, then she may complain of monthly nosebleeds, engorgement of the mammary glands and pulling pains in the lower abdomen, which are accompanied by the accumulation of menstrual flow, since their outflow with the above diagnosis is impossible.
A similar phenomenon leads to the appearance of tumor-like formations - the so-called hematocolpos. As they grow, sharp bursting pains appear in the lower abdomen, and when suppuration of deposited secretions occurs, the temperature rises, favorable conditions for sepsis are created. The patient in this case shows an urgent operation.
In the absence of the uterus, tumors do not form, since there is no organ that secrete blood.
Aplasia is not always a death sentence
The effect on the human body of aplasia of different organs, tissues or parts of the body is different. Some types of aplasia (lack of cerebral hemispheres, heart muscle, both kidneys, etc.) are incompatible with life. Others can cause severe disturbances in the functioning of the body, and without surgical intervention will lead to the death of the patient (diaphragmatic hernia or Hirschsprung’s disease).
But the lack of part or the entire limb, as well as uterine aplasia, are completely compatible with life. And the undevelopment of one paired organ, for example, with unilateral aplasia of the kidney, is sometimes completely compensated by the hypertrophy of another, and due to this it may not clinically manifest itself throughout the patient’s life.