Glossary

deletion
gene or chromosome aberration in which genetic material is lost; single nucleic bases (point mutation), larger base sequences, or even entire chromosomes may be affected (deleted).
Example / Relevance Pediatrics: in some tumour diseases (e.g. some neuroblastomas), a 1p deletion may be present. This means that genetic material has been lost in the short arm of chromosome 1. Neuroblastomas with 1p deletion are associated with an unfavourable prognosis.

Denys-Drash syndrome (Abrev.: DDS) syn. WT1-associated syndrome
rare disease characterized by severe genital malformations (pseudohermaphroditism), malformation of the gonads, kidney disease (proliferation of connective tissue cells in the renal corpuscles, mesangiosclerosis) with early renal failure and an increased risk of Wilms tumours and tumours of the gonads (gonadoblastoma); DDS syndrome is therefore also one of the cancer predisposition syndromes. In most patients with this disease, there is a change (mutation) in a gene on chromosome 11, called the Wilms tumour gene (WT1 gene). This gene probably plays an essential role in the development of the genitourinary system. If it is present in mutated form, there is generally an increased risk (74–90%) of developing a Wilms tumour.

diabetes insipidus
increase in urine excretion with urine volumes of several litres per day; as the body loses a lot of water, the body and mucous membranes dehydrate and patients feel very thirsty. The cause is usually a disorder in the posterior lobe of the pituitary gland and/or diencephalon resulting in decrease or lack of antidiuretic hormone (ADH) function.
Example / Relevance Pediatrics: diabetes insipidus can be caused by tumours in the area of the diencephalon and associated hormonal dysfunction of the hypothalamus and/or pituitary gland, and it may require hormone replacement therapy.

diagnostics
methods / measures for the detection of a disease
Main Information Document: Diagnostic procedures

Diamond-Blackfan anaemia (Abrev.: DBA) syn. chronic congenital hypoplastic anaemia
hereditary blood disorder characterised by impaired bone marrow function, growth disorders and malformations (the latter in approximately 40 % of patients); there is also an increased risk of developing acute myeloid leukaemia or myelodysplastic syndrome (MDS). The disease is caused by a disorder of the formation of red blood cells in the bone marrow (white blood cells and platelets are not affected), which is associated with chronic severe anaemia and must be treated for life. The disease usually occurs in early childhood.

diaphragm
a thin muscle below the lungs; separates the chest and abdominal cavities and supports breathing

diencephalon
vital part of the brain with function for numerous life processes; it connects to the brainstem towards the cerebrum and consists of functionally different sections. The "thalamus", for example, decides which sensory impressions should penetrate into consciousness and are to be sent to the appropriate processing centers. The "hypothalamus" serves as a mediator between the hormonal and nervous systems and controls, among other things, important metabolic processes (e.g. heat and water balance, carbohydrate, fat, protein metabolism, blood pressure). Together with the pituitary gland, it regulates the activity of subordinate glands. Other parts of the diencephalon are responsible for muscle activities and for controlling the day-night rhythm.

differential diagnosis (Abrev.: DDx)
any possible diagnosis to be considered in the case of a disease
Example / Relevance Pediatrics: the following differential diagnoses, for example, must be taken into account as a cause of headaches: anaemia, meningitis, lack of fluids (in case of diarrhea, vomiting), increased pressure in the head (in the case of a brain tumour, as a side effect of irradiation of the brain, untreated hydrocephalus requiring drainage), side effects of certain cytostatics.

differentiated
here: mature, functional; differentiated cells/tissues are fully developed structures with special tasks; they have no or only limited ability to divide. The development from undifferentiated to differentiated cells and tissues (differentiation) takes place gradually, so there are many different stages of differentiation.
Example / Relevance Pediatrics: the degree of differentiation of cancer cells refers to their similarity or difference to healthy, functional cells of the organ in which the tumour originated: highly differentiated cancer cells largely resemble normal cells, while undifferentiated cancer cells differ greatly from them. As a rule, the more undifferentiated a tumour is, the more malignant it is.

differentiation
here: development of immature cells / immature tissue into mature tissue with specialised tasks; differentiation is based on a hereditary blueprint.
Example / Relevance Pediatrics: for tumours, the more immature a tumour tissue is, i.e. the less its structure and function correspond to that of the mother tissue, the more undifferentiated and usually also higher malignant it is.

DNA
abbreviation for deoxyribonucleic acid; it carries the genetic information and is found in all living beings. DNA contains the genes that provide the information for the production of ribonucleic acids (RNA) or proteins. It is a large molecule consisting of two nucleic acid chains twisted into a double helix. The individual chains consist of a sequence of four different building blocks (bases), the order (sequence) of which determines the genetic code.

Down syndrome
congenital disorder associated with maldevelopment of tissues and organs, mental retardation that varies from person to person, short stature and malformations in the facial area; patients with Down syndrome also have an increased risk of developing cancer, especially leukaemia. Down syndrome is caused by a chromosomal alteration: chromosome 21 is present in every cell of the body in three copies instead of two (Trisomy 21). As a result, tissues and organs grow more slowly, remain immature, age faster and have malformations.

drainage
here: drainage of pathological or increased natural body fluids to the outside, for example drainage of cerebrospinal fluid from the cerebral ventricles or of pathological fluid accumulation from the pleura (pleural drainage);
Example / Relevance Pediatrics: some brain tumours, for example tumours in the posterior cranial fossa, can cause impaired drainage of the cerebrospinal fluid and, thus, certain acute signs of illness (headaches, impaired consciousness, paralysis, and hydrocephalus), some of which require drainage before the actual tumour treatment. Tumours in the abdomen and chest (e.g. lymphomas) can lead to fluid accumulation in the abdomen (ascites) or pleura (pleural effusion), some of which must also be drained.

dyskeratosis congenita syn. Zinsser-Cole-Engman syndrome
hereditary disorder that affects multiple organ systems; the syndrome is primarily characterised by abnormal pigmentation of the skin and mucous membranes, as well as growth disorders of fingernails and toenails. Causative treatment is often only possible through a stem cell transplant. Life-threatening symptoms of the disease include, for example, disorders of bone marrow function with suspension of normal blood formation (bone marrow suppression) and consequently a lack of red and white blood cells as well as platelets, myelodysplastic syndrome (MDS), or aplastic anaemia.

dysplasia
malformation or maldevelopment of a tissue with insufficient differentiation (maturation)
Example / Relevance Pediatrics: tissue dysplasia can be the precursor of cancer.