Rickets
A childhood disease in which growing bones fail to harden properly, usually from a lack of vitamin D (and the calcium and phosphate it controls). It causes soft, weak and deformed bones — classically bowed legs — and is prevented and treated with vitamin D and calcium.
What it is
Rickets is a disease of the growing skeleton in children, in which new bone is laid down but does not mineralise (harden) properly, leaving it soft and weak. Its usual cause is a lack of vitamin D, which the body needs to absorb calcium and phosphate from food and to deposit them in bone. Vitamin D deficiency arises from too little sunlight (the skin makes vitamin D from sun), darker skin, exclusive breastfeeding without vitamin D drops, and diets low in vitamin D and calcium. Less commonly, rickets results from an inherited problem handling phosphate or vitamin D. Because the bones are still growing and soft, rickets causes visible changes: bowing of the legs once a child starts to bear weight, thickening at the wrists, knees and rib ends (the 'rachitic rosary'), a soft skull, delayed closure of the fontanelle, and delayed walking and growth. Children may also have bone pain, muscle weakness, irritability, and are prone to fractures; a very low calcium can cause seizures in infants. In adults, the equivalent (bone already grown) is osteomalacia. Rickets is largely preventable and very treatable with vitamin D and calcium, so recognising it matters.
Key lab markers
- Vitamin D (25-hydroxyvitamin D) — typically low; the usual underlying cause.
- Calcium — may be low or low-normal.
- Phosphate — often low.
- Alkaline phosphatase — typically high, reflecting active bone turnover; a useful clue.
- Parathyroid hormone (PTH) — often raised in response to low calcium.
- X-rays of the wrists or knees — show the characteristic changes at the growth plates.
Symptoms
- Bowing of the legs (or knock-knees) once weight-bearing
- Swelling or thickening at the wrists, knees and rib ends
- Bone pain or tenderness, reluctance to walk
- Muscle weakness, delayed walking and milestones
- Slowed growth, a soft skull, delayed fontanelle closure
- Irritability; sometimes seizures in infants (from very low calcium)
- Prone to fractures
Related symptoms
Related lab panels
When to discuss with a doctor
Rickets should be considered in a child with bowed legs, delayed walking, bone pain, or poor growth, particularly with risk factors such as limited sun exposure, darker skin, or exclusive breastfeeding without vitamin D supplementation — and it warrants assessment by a doctor. It is worth acting on because it is both preventable and very treatable: vitamin D (with adequate calcium) usually corrects it, and deformities in young children often remodel and improve once the bone hardens. Because low vitamin D and calcium are common in infancy, many guidelines recommend routine vitamin D drops for breastfed babies to prevent rickets in the first place. A very low calcium causing seizures or breathing problems in an infant is an emergency. Mediora.AI can flag the tell-tale pattern of low vitamin D with a raised alkaline phosphatase and altered calcium and phosphate; diagnosis and treatment of a child with suspected rickets belong with your doctor.