Symptoms & Warning Signs

Vitamin D-Dependent Rickets (VDDR) affects the body in ways that go far beyond simple bone health. Because vitamin D and calcium are essential for everything from nerve signals to tooth development, the symptoms can appear in many different systems at once ^[1]. Understanding these signs can help you track your child’s progress as they begin treatment.

Emergency Guidance: When to Act Fast

Because VDDR can cause severe hypocalcemia (low blood calcium), it is critical to know when to seek immediate help ^[2]:

• Go to the ER immediately if your child experiences a seizure, severe muscle spasms (tetany), extreme lethargy, or sudden breathing difficulties. These are medical emergencies caused by critically low calcium ^[3].
• Call your doctor/endocrinologist if you notice gradual changes like increased irritability, a regression in physical milestones (e.g., they stop crawling), or a “floppy” appearance to their muscles.

Skeletal Symptoms: More Than Just “Bowed Legs”

The most visible signs of VDDR involve the skeleton. When the body cannot absorb enough calcium, the bones remain soft and pliable ^[3].

• Lower Limb Deformities: This often appears as “bowing” (knees curving outward) or “knock-knees” (knees curving inward) once a child starts bearing weight or walking ^[1].
• Widened Joints: You may notice that your child’s wrists or knees look unusually thick or swollen ^[4].
• Rachitic Rosary: This is a term used to describe small, bead-like bumps that can be felt along the ribs where they meet the chest bone ^[1].
• Delayed Growth: Children with VDDR often fall behind on growth charts, as their bones cannot lengthen properly without mineralization ^[3].

Neurological and Muscular Symptoms

Calcium is the “electricity” of the nervous system. When levels drop, it destabilizes nerve cells ^[3].

• Hypocalcemic Seizures: When calcium in the blood drops too low, it can cause nerve cells to fire uncontrollably, leading to seizures ^[5]. This is often the first sign that brings a family to the hospital.
• Hypotonia (Muscle Weakness): Children may appear “floppy” or have very low muscle tone ^[3]. This weakness can lead to a regression of milestones, where a child who was previously sitting up or crawling suddenly loses that ability ^[2].

Extra-Skeletal Symptoms: Teeth and Hair

Because the genetic mutations in VDDR affect how cells respond to vitamin D throughout the body, symptoms can appear in unexpected places.

• Dental Defects: You may notice enamel hypoplasia—pitting, grooves, or thin enamel on the teeth ^[6]. Teeth may also be slow to come in (delayed eruption) or may be missing entirely.
• Alopecia (Hair Loss): This is a hallmark sign of Type 2 VDDR ^[7]. It occurs because the Vitamin D Receptor (VDR) is essential for the natural cycle of hair follicles ^[8]. In Type 2, the receptor is broken, and hair cannot grow properly, often leading to total hair loss from early infancy ^[2]. Note: Alopecia does NOT happen in Type 1 or Type 3 VDDR because the receptor itself still works ^[9].