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Pathological anatomy · Chapter 24. Childhood Diseases

Pediatric infectious diseases

Infectiones infantum

Despite the topic title, the presented material describes chromosomal and gene disorders in childhood. These are pathologies resulting from mutations at the gene or chromosome level, clinically manifesting as multiple congenital malformation complexes and severe functional impairments.

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Mutation frequencyDetected in 0.5% of live newborns and in 10–15% of all congenital malformations.
Patau markerAn overly lobulated microcystic kidney is a specific sign of trisomy 13.
Turner lethality90% of embryos with monosomy X die intrauterine, with only 10% being born.
Gene disordersAbout 4,500 diseases inherited in a Mendelian pattern have been described.
4 min readFor medical studentsUpdated Sep 25, 2026
Material prepared by WhiteCoat Pro editorial team based on platform study guidesReviewed by medical editor: Aulov A. A., general practitioner · 09/24/2026

General characteristics and types of mutations

Most chromosomal abnormalities are incompatible with life and are eliminated in the early stages of embryogenesis. Viable fetuses predominantly exhibit autosomal trisomies, sex chromosome polysomies, and the single monosomy variant — monosomy X.

Pathologies are based on different types of rearrangements: deletions (forming partial monosomy), duplications (partial trisomy), inversions, and translocations. The clinical picture across all forms is centered around multiple congenital malformations.

Autosomal trisomies

Down syndrome (Trisomy 21) Frequency 1:700–1:800, risk increases sharply in mothers over 35 years of age.

  • Phenotype: mongoloid slant of the eyes, epicanthus, flat nasal bridge, macroglossia, brachycephaly, clinodactyly of the fifth fingers, single transverse palmar crease, and Brushfield spots on the iris. Marked muscular hypotonia.
  • Internal organs: atrioventricular septal defect (ventricular septal defect and deformation of the anterior leaflet of the mitral valve), duodenal and esophageal atresia/stenosis, renal dysplasia. Hypoplasia of the frontal lobes of the brain is characteristic.
  • Complications: secondary immunodeficiency and an increased predisposition to leukemias.

Patau syndrome (Trisomy 13) Frequency 1:5000–1:7000.

  • Manifestations: pronounced prenatal hypoplasia, bilateral cleft lip and palate, micrognathia, scalp defects, polydactyly.
  • Malformations: arhinencephaly, microcephaly, Meckel's diverticulum, ectopic spleen in the pancreas. The diagnostic marker is an overly lobulated microcystic kidney. Only 5% of children live past one year.

Edwards syndrome (Trisomy 18) Frequency 1:5000–1:7000.

  • Phenotype: dolichocephaly, microstomia, flexed fingers of the hand, rocker-bottom foot (short and wide hallux).
  • Malformations: aplasia of one of the cusps of the pulmonary valve or aortic valve, malrotation of the intestine, esophageal atresia.
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Sex chromosome abnormalities and triploidies

Turner syndrome (45, X0) Frequency — 1:5000 live-born girls (half of the cases are true monosomy, the remaining 50% are due to isochromosomes and mosaicism, in which the clinical presentation is mild).

  • Manifestations: short stature, webbed neck, lymphedema of the hands and feet in newborns.
  • Organs: coarctation of the aorta, horseshoe kidney, gonadal dysgenesis leading in older age to primary amenorrhea and infertility.

Triploidy syndrome (69, XXY / 69, XXX) Rare in newborns, but accounts for over 20% of all spontaneous abortions. Manifests with microphthalmia, widely spaced palpebral fissures, and syndactyly. Internal malformations include hydrocephalus, spinal hernias, and cystic renal dysplasia. Placental pathology is specific — its mass is increased, and chorionic villi undergo cystic transformation.

Microcytogenetic and gene syndromes

These pathologies are detected only by molecular cytogenetic methods and are associated with the loss or duplication of micro-regions or gene mutations.

  • DiGeorge syndrome (del 22q11). Aplasia of the thymus and parathyroid glands. Leads to hypocalcemic seizures.
  • Miller–Dieker syndrome (del 17p13). Manifests with lissencephaly (absence of cortical gyri) and seizures.
  • Beckwith–Wiedemann syndrome (add 11p15). Characterized by gigantism, macroglossia, visceromegaly, and umbilical hernia.
  • Tricho-rhino-phalangeal syndrome type 2 (del 8q23-24). Multiple exostoses, facial anomalies, short stature.
  • Gene pathologies (autosomal dominant and recessive): Noonan syndrome (PTPN11 mutation, pulmonary stenosis), Holt–Oram syndrome (TBX5, aplasia of the thumb and radius), and Meckel–Gruber syndrome (MKS1, occipital encephalocele and polycystic kidneys).

Briefly: answers to topical questions

What are the clinical and morphological manifestations of DiGeorge syndrome?

  • DiGeorge syndrome is a microcytogenetic syndrome caused by a deletion in the 22q(11) region. Clinically and morphologically, it manifests as aplasia or hypoplasia of the thymus and aplasia of the parathyroid glands, leading to the development of hypocalcemic seizures. Facial dysmorphism, defects of the heart and great vessels, interruption of the aortic arch, Tetralogy of Fallot, truncus arteriosus, as well as congenital agenesis of the parathyroid and thymus glands are also observed.
How to memorize

To remember 15th chromosome imprinting: P — Prader–Willi syndrome (inherited from Papa), M — Angelman syndrome (inherited from Mother).

Class and exam questions

What is genomic imprinting and how does it manifest?

This is the dependence of the phenotype on which parent the mutation was inherited from. A striking example is the 15q11-12 deletion: if the segment is inherited from the father, Prader-Willi syndrome develops (obesity, hypogonadism); if from the mother, Angelman syndrome (atonia, bouts of laughter, epilepsy).

What specific renal changes are characteristic of Patau syndrome?

For trisomy 13, an overly lobulated microcystic kidney is a typical diagnostic sign.

Cardiovascular system disorders in Edwards syndrome?

Aplasia of one of the cusps of the pulmonary or aortic valves, as well as various septal defects, is of major diagnostic significance.

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What else to study on this topic

  • Pathogenesis of immunodeficiency and the risk of leukemia in Down syndrome
  • Comparative characteristics of CNS malformations in trisomies 13, 18, and 21
  • Mechanisms of cystic transformation of chorionic villi in triploidy
  • Mosaicism and isochromosomes in the development of atypical forms of Turner syndrome

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Other topics in «Chapter 24. Childhood Diseases»

Perinatal pathologyHemolytic Disease of the NewbornIntrauterine infectionsBirth traumaNeonatal asphyxiaPneumonia in childrenDigestive system diseases in childrenCongenital malformationsRicketsPediatric tumorsDown syndromeSyndromes in tuberculosisMetaplasia
The entire section «Chapter 24. Childhood Diseases»

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