Vitamin D is classified as a vitamin, but it actually acts as a hormone, in its activated form. Vitamin D is involved in numerous processes such as intestinal absorption of calcium, bone metabolism, the immune response and it also has an important role in respiratory function.
There are pathologies such as Osteogenesis Imperfecta, Ehlers-Danlos syndrome and deficiency rickets that negatively impact the absorption and metabolism of vitamin D.
Patients affected by these pathologies can suffer from hypovitaminosis D, with serious consequences for health.
Osteogenesis Imperfecta (OI) is a rare genetic disorder, mainly associated with inherited variants of the COL1A1 and COL1A2 genes. It is a systemic pathology that affects connective tissue. The most common clinical manifestations are bone fragility, skeletal deformity, growth failure, increased risk of fractures, dentinogenesis and a peculiar blue-gray coloration of the sclera. OI can occur in different forms, mainly differentiated into 4 phenotypes (I-II-III-IV), with different degrees of severity for the life of the subject. Phenotypes have highly different consequences on patient's life expectancy and all forms have a strong impact on formation and quality of the collagen that forms bones.
The Ehlers-Danlos Syndrome (EDS) includes a group of genetic disorders of the connective tissue. To date, 13 subtypes of EDS are known, divided into classic forms (I and II type), hypermobilized forms, vascular forms, forms with kyphoscoliosis, forms with arthrochalasia, forms with dermatosparaxia. EDS is characterized by a generalized presence of defective collagen. All connective tissues (bone, cartilage, blood vessels, joints, dermis) are weakened. Bone problems are mainly associated with EDS forms with kyphoscoliosis. The most common clinical manifestations of EDS are: hypermobility of the joints, abnormal skin discoloration and delayed wound healing.
The reduction in bone mass has been well documented since the 1990s in the various forms of EDS. Hypovitaminosis D is the most important risk factor, although not the only one, for bone fragility. Hypovitaminosis D is mainly present in patients with dolicocolon (excessive lengthening of the colon) and gastroesophageal reflux.
Rickets is a rare disease that arises in pediatric age and manifests itself as a mineralization defect of the newly formed bone tissue. As a consequence, bones are more fragile and deformable. Other typical clinical features can be: bone deformity and pain, rickets rosary, muscle weakness, lung infections, osteopenia, headache, growth retardation.
Numerous conditions can originate rickets, but the main cause is a lack of calcium and / or vitamin D. The lack of vitamin D (hypovitaminosis D) prevents the absorption of calcium in the intestine, thus leading to a lack of calcium (hypocalcemia ).
Based on the etiopathogenesis of rickets it is possible to differentiate it into two main classes: deficient rickets and hypophosphatemic rickets.
Deficient rickets is characterized by vitamin D deficiency, mainly caused by:
Hypophosphatemic rickets is a disease characterized by low serum phosphate levels and is mainly due to hereditary genetic defects. The resulting rickets generally do not respond to vitamin D.
Although the etiopathogenesis is different, the consequences on the health of the bone tissue are similar but depending on the type of rickets it is necessary to resort to different therapeutic strategies.
Deficient rickets is the most common form and vitamin D deficiency is the most frequent cause. Restoring adequate levels of vitamin D is essential to contrast the evolution of deficiency damage.
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