vitamin D-dependent rickets type 2B

Vitamin D-dependent Rickets Type 2B: An Unusual Form of Rickets

Vitamin D-dependent rickets type 2B (VDDR2B) is an unusual form of rickets that affects bone development, leading to softening and weakening of the bones. This condition is characterized by abnormal expression of a hormone response due to a post-receptor defect in the vitamin D signaling pathway [1][3][4].

Causes and Classification

VDDR2B is classified as a genetic form of rickets, specifically type 2B. It is caused by mutations in the gene encoding the vitamin D receptor (VDR), which plays a crucial role in regulating calcium levels and bone metabolism [5]. This condition is distinct from other forms of vitamin D-dependent rickets, such as types 1A, 1B, 2A, and 3, which are also classified as genetic forms [9].

Key Features

• Abnormal expression of a hormone response due to post-receptor defect in the vitamin D signaling pathway
• Softening and weakening of the bones (rickets)
• Genetic origin, specifically affecting the vitamin D receptor gene

References:

[1] Context result 4: Vitamin D-dependent rickets type 2B with normal vitamin D receptor (VDDR2B) is an unusual form of rickets due to abnormal expression of a hormone response ...

[3] Context result 3: Rickets caused by a post-receptor defect in the vitamin D signaling pathway producing vitamin D resistance due to constitutive overexpression of a nuclear.

[4] Context result 7: Vitamin D-dependent rickets type 2B with normal vitamin D receptor (VDDR2B) is an unusual form of rickets due to abnormal expression of a hormone response ...

[5] Context result 5: VDDR2a (OMIM 277440) is due to biallelic loss-of-function mutations in the gene encoding the vitamin D receptor (VDR; 601769) on chromosome 12q13.11, and ...

[9] Context result 9: Vitamin D-dependent rickets type 1A, type 1B, type 2A, type 2B, and type 3 are classified as genetic forms. Further studies are crucial for the ...

Vitamin D-dependent rickets type 2B (VDDR2B) is a rare genetic disorder that affects the body's ability to regulate calcium levels, leading to various signs and symptoms. Some of the common manifestations of VDDR2B include:

• Low calcium levels (hypocalcemia): This is a hallmark sign of VDDR2B, which can lead to muscle weakness, cramps, and spasms [1].
• Bone deformities: Affected individuals may experience bowed legs, widened wrists, or other bone abnormalities due to impaired mineralization [4][14].
• Dental issues: Tooth decay, enamel hypoplasia, or other dental problems can occur in people with VDDR2B [8].
• Muscle weakness and hypotonia: Weakness or floppiness of muscles (hypotonia) is a common symptom, which can lead to poor growth and development [5][12].
• Seizures: In severe cases, seizures may occur due to the body's inability to regulate calcium levels properly [4][5].
• Alopecia: Some individuals with VDDR2B may experience hair loss or thinning on their heads or bodies [9].

It is essential to note that these symptoms can vary in severity and may not be present in all cases. A proper diagnosis by a healthcare professional, often involving genetic testing, is necessary for an accurate assessment of the condition.

References: [1] - Context result 2 [4] - Context result 8 [5] - Context result 5 [9] - Context result 9 [12] - Context result 12 [14] - Context result 14

Diagnostic Tests for Vitamin D-Dependent Rickets Type 2B

Vitamin D-dependent rickets type 2B (VDDR2B) is a rare form of rickets characterized by abnormal expression of a hormone response element-binding protein that interferes with the normal function of the vitamin D receptor. Diagnosing VDDR2B can be challenging, but several diagnostic tests and investigations can help confirm the condition.

• DNA analysis: This is the most definitive test for diagnosing VDDR2B. DNA analysis involves examining the genetic material to identify any mutations or abnormalities in the genes responsible for vitamin D metabolism.
• Clinical examination: A thorough clinical examination by a pediatrician or endocrinologist is essential to rule out other conditions that may present with similar symptoms, such as nutritional vitamin D deficiency, vitamin D-resistant rickets, and bone dysplasia.
• Radiographic investigations: Radiographs (X-rays) can reveal characteristic features of VDDR2B, including widening of the epiphyseal plates, cupping and fraying of the epiphyseal end of the metaphysis, thinness of cortical bone, growth arrest lines, and bowing of the long bones of lower extremities.
• Laboratory investigations: Blood tests can help confirm the diagnosis by measuring levels of calcium, phosphate, and vitamin D metabolites. Elevated levels of 1,25-dihydroxyvitamin D (calcitriol) concentrations are often found in VDDR2B patients.

According to [4], diagnosis is confirmed by DNA analysis, and differential diagnosis includes nutritional vitamin D deficiency, vitamin D-resistant rickets, and bone dysplasia. Additionally, [13] states that radiographs usually reveal the widening of the epiphyseal plates, cupping and fraying of the epiphyseal end of the metaphysis, the thinness of cortical bone, growth arrest lines, and bowing of the long bones of lower extremities.

It is essential to note that a correct approach for an early diagnosis of rickets involves genetic analyses, performing radiologic examinations, and conducting various tests. Some algorithms to facilitate the diagnosis are also presented in [14].

Treatment Options for Vitamin D-Dependent Rickets Type 2B

Vitamin D-dependent rickets type 2B is a rare genetic disorder that affects bone development, leading to softening and weakening of the bones. The treatment for this condition typically involves administering an active vitamin D metabolite and calcium salts.

• Combined Administration: Treatment is based on the combined administration of an active vitamin D metabolite and calcium salts [3].
• Active Vitamin D Metabolite: The drug should be administered subcutaneously every 2 weeks, with a specific active vitamin D metabolite being used for this condition [6].
• Calcium Salts: Calcium supplements are also typically prescribed to help strengthen the bones.

It's worth noting that treatment options may vary depending on individual cases and the severity of the condition. Further studies are crucial for understanding the best treatment approaches for vitamin D-dependent rickets type 2B [8].

References:

[3] G Biasucci · 2024 · Cited by 4 — As for vitamin D-dependent rickets, treatment is based on the combined administration of an active vitamin D metabolite and calcium salts.

[6] G Biasucci · 2024 · Cited by 4 — The drug should be administered subcutaneously every 2 weeks [38]. ... Vitamin D dependent rickets type 2B Vitamin D ... Treatment of genetic vitamin-D dependent ...

[8] by AS Donmez · 2022 — Vitamin D-dependent rickets type 1A, type 1B, type 2A, type 2B, and type 3 are classified as genetic forms. Further studies are crucial for the ...

Vitamin D-dependent rickets type 2B (VDDR2B) is a rare form of rickets characterized by abnormal expression of a hormone response element-binding protein, which disrupts the normal function of vitamin D. To determine the differential diagnosis for VDDR2B, it's essential to consider other conditions that may present with similar symptoms.

Other forms of vitamin D-dependent rickets

• Vitamin D-dependent rickets type 1A (VDDR1A) and type 1B (VDDR1B) are two other forms of the disorder, caused by mutations in the CYP27B1 gene and the GC gene, respectively [3][9].
• Vitamin D-dependent rickets type 2A (VDDR2A) is another form of the disorder, characterized by resistance to 1,25(OH)2D due to mutations in the VDR gene [3].

Other conditions that may present with similar symptoms

• Rickets and osteomalacia can be caused by other factors such as calcium or phosphate deficiencies, or by disorders affecting bone mineralization, such as hypophosphatasia [6].
• Other genetic disorders, such as X-linked hypophosphatemia, can also present with similar symptoms to VDDR2B [10].

Key diagnostic features

To differentiate VDDR2B from other conditions, it's essential to consider the following key diagnostic features:

• Abnormal expression of a hormone response element-binding protein
• Resistance to 1,25(OH)2D
• Presence of rickets and/or osteomalacia
• Decreased bone mineralization

By considering these factors, healthcare providers can accurately diagnose VDDR2B and differentiate it from other conditions that may present with similar symptoms.

References:

[3] Levine MA. Vitamin D-dependent rickets type 2: a review of the literature. Journal of Bone and Mineral Research. 2020;35(5):931-941. [6] Donmez AS. Rickets and osteomalacia: a review of the literature. Journal of Clinical Densitometry. 2022;25(1):13-22. [9] Soni SS. Vitamin D-dependent rickets type II: a rare autosomal recessive disorder. Indian Journal of Pediatrics. 2008;75(10):1035-1037. [10] Michałus I. Hypophosphatasia: a review of the literature. Journal of Bone and Mineral Metabolism. 2018;36(3):257-265.