Parenchymal Carbohydrate Dystrophies

Frequently asked questions

Which hereditary storage diseases (glycogenoses) belong to parenchymal carbohydrate dystrophies?

Parenchymal carbohydrate dystrophies include hereditary enzymopathies classified into several types depending on the enzyme defect and alterations in glycogen structure.

• Type I — von Gierke disease (glucose-6-phosphatase deficiency).
• Type II — Pompe disease (alpha-1,4-glucosidase deficiency).
• Type III — Cori or Forbes-Cori disease (amylo-1,6-glucosidase deficiency).
• Type IV — Andersen disease (D-1,4-glucan-α-glucosyltransferase deficiency).
• V type — McArdle disease (myocyte glycogen phosphorylase deficiency).
• VI type — Hers disease (hepatocyte glycogen phosphorylase deficiency).
• VII type — Tarui disease (phosphofructomutase deficiency).
• VIII type — (phosphorylase kinase deficiency in hepatocytes).

Mutations in which gene and protein are the etiological cause of cystic fibrosis?

The etiological cause of cystic fibrosis is a mutation in the gene localized in the middle of the long arm of chromosome 7 (7q31–32). This gene encodes a specific protein called the cystic fibrosis transmembrane conductance regulator (CFTR). In most Caucasian patients, the disease is caused by a mutation leading to the deletion of phenylalanine at position δF508, which causes a severe form of the pathology. Currently, approximately 2,000 different mutations of this gene capable of causing the clinical picture of the disease have been identified.

Which histochemical staining methods are used on microsections to detect glycogen and glycoproteins?

Specific histochemical reactions and stains are used on microsections to detect glycogen and glycoproteins.

• PAS reaction (Periodic acid–Schiff) — detects polysaccharides and glycoproteins by oxidation with periodic acid followed by Schiff's reaction (staining red, purple, or dark red).
• Best's carmine stain — used to differentiate glycogen, staining it red.
• Enzymatic control — treatment of sections with amylase combined with the PAS reaction for precise glycogen identification.
• Toluidine blue or methylene blue stain — used to detect glycoproteins through metachromasia (change in dye color).

What secondary pulmonary complications develop against the background of chronic mucus stasis in the bronchi in cystic fibrosis?

Against the background of chronic viscous secretion stasis and airway obstruction in cystic fibrosis, a number of severe secondary pulmonary complications develop.

• Infectious and inflammatory processes — foci of bronchopneumonia, chronic abscesses, and rapid bacterial colonization.
• Structural changes — formation of cylindrical bronchiectasis, development of atelectasis, pneumosclerosis, and pulmonary emphysema.
• Severe respiratory states — pneumopyothorax, hemoptysis, pulmonary hemorrhage, and pulmonary hypertension.
• Specific complications — allergic bronchopulmonary aspergillosis.

How does the electrolyte composition of sweat gland secretions change in cystic fibrosis for the sweat test?

In cystic fibrosis, chloride transport defects reduce sodium chloride reabsorption, leading to a pathological increase in electrolyte concentrations in sweat gland secretions. Chloride concentrations in the sweat of patients increase 3- to 5-fold. The sweat test (Gibson-Cook method) is used for diagnosis, evaluating chloride or sodium levels:

Result	Chloride Concentration
Normal	up to 30 mmol/L
Borderline result	30–59 mmol/L
Pathology (Cystic Fibrosis)	$\ge$ 60 mmol/L

What irreversible structural changes in the liver result from prolonged bile stasis in cystic fibrosis?

Prolonged bile stasis in cystic fibrosis leads to progressive fibrotic processes and irreversible remodeling of the liver parenchyma. Initially, focal fibrosis, steatosis, and cholangitis are observed in the organ. With a prolonged disease course, some patients develop biliary cirrhosis, which may be accompanied by intrahepatic portal hypertension syndrome. Structural changes are staged according to the METAVIR score, with the final stage (F4) being established cirrhosis. Decompensation of these pathological changes is one of the causes of mortality.

What is the primary cause of parenchymal carbohydrate dystrophies?

This group of dystrophies is based on impaired cellular metabolism of two main classes of carbohydrates: glycogen (storage carbohydrate) or glycoproteins (complex protein-carbohydrate complexes).

How does the nature of glandular secretion change in cystic fibrosis?

A qualitative change occurs in the mucus secreted by the epithelium: it loses normal fluidity, becoming pathologically thick and viscous, which makes its adequate excretion impossible.

What is cystic fibrosis from the perspective of pathological anatomy?

It is the morphological manifestation of mucoviscidosis, in which retention cysts (dilated ducts filled with secretion) form due to impaired mucus drainage, and sclerosis (proliferation of connective tissue) develops around them.

What determines the outcome of the disease for the affected organ?

The outcome is determined by the degree and duration of excessive mucus production. A short-term process may allow complete epithelial regeneration, whereas a prolonged process leads to mucosal atrophy and irreversible loss of organ function.