Vitamin D-dependent rickets

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Vitamin D-dependent rickets is a group of disorders that are characterized by soft, weak bones (rickets). In people with these conditions, the process by which minerals are deposited into developing bones (mineralization) is disrupted. The long bones in the arms and legs are particularly affected. People with vitamin D-dependent rickets have problems using vitamin D, which helps maintain the proper levels of calcium and phosphate in the blood. These minerals are needed for the normal development of strong bones and teeth.

There are several forms of vitamin D-dependent rickets: type 1A (VDDR1A), type 1B (VDDR1B), type 2A (VDDR2A), type 2B (VDDR2B), and type 3 (VDDR3). The types are distinguished by their genetic cause.

The signs and symptoms of vitamin D-dependent rickets often begin in infancy. Infants with vitamin D-dependent rickets may have weak muscle tone (hypotonia) and fail to grow or gain weight at the expected rate (failure to thrive). When affected children begin to walk, they may develop abnormally curved (bowed) legs because the bones are too weak to bear weight. The weakened bones are often painful and are prone to fractures. Bone growth is often delayed, and affected individuals may be shorter than their peers. Additional skeletal features include enlargement of the skull, the wrists, and the ends of the ribs.

Affected individuals may also have dental abnormalities, such as delayed tooth formation and thin tooth enamel. Some people with vitamin D-dependent rickets who have very low levels of calcium in the blood can have muscle cramps, tingling sensations (paresthesias), or seizures. Hair loss (alopecia) has been reported in some individuals with VDDR2A.

With early treatment, affected individuals may have less-severe skeletal signs and symptoms and fewer long-term health issues. Unlike with some other forms of rickets, vitamin D-dependent rickets cannot be treated with standard doses of vitamin D.

Inheritance

From: MedlinePlus Genetics, National Library of Medicine

Autosomal dominant; Autosomal recessive

Understanding terms used in the source

These definitions explain medical words used above. A definition is not evidence that another condition is present, and it does not predict how a symptom will develop. Ask the clinician which terms apply to the actual examination or test result.

Failure to thrive

Failure to thrive (FTT) refers to a child whose physical growth is substantially below the norm.

Hypotonia

Hypotonia is an abnormally low muscle tone (the amount of tension or resistance to movement in a muscle). Even when relaxed, muscles have a continuous and passive partial contraction which provides some resistance to passive stretching. Hypotonia thus manifests as diminished resistance to passive stretching. Hypotonia is not the same as muscle weakness, although the two conditions can co-exist.

Affected

This term applies to a family member who is diagnosed with the same condition as the individual who is the primary focus of investigation (the proband).

Alopecia

A noncongenital process of hair loss, which may progress to partial or complete baldness.

When it may begin

From: MedlinePlus Genetics, National Library of Medicine

The signs and symptoms of vitamin D-dependent rickets often begin in infancy. Infants with vitamin D-dependent rickets may have weak muscle tone (hypotonia) and fail to grow or gain weight at the expected rate (failure to thrive).

Inheritance in the source

From: MedlinePlus Genetics, National Library of Medicine

Autosomal dominant; Autosomal recessive

Which doctor should you see?

The suggested department for discussing Vitamin D-dependent rickets is Endocrinology, with a endocrinologist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Which hormone or metabolic finding is important in this case?
• How should test timing and current medicines be taken into account?
• What follow-up would show whether the care plan is working?

Treatment discussions and follow-up

Where the source describes treatments, these are an overview of possible care, not a prescription for an individual. Ask which option applies to the confirmed diagnosis, what benefit is expected, what adverse effects to watch for and how progress will be assessed. Availability, approvals and local practice can differ from the country described in the source.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.