Rickets, less commonly known as rachitis, essentially refers to osteomalacia in the paediatric population that occurs before fusion of the growth plate.
Rickets is seen in a number of distinct populations which include 4:
- premature infants (especially if on parenteral nutrition)
- unbalanced infant nutrition
- protracted exclusive breastfeeding
- non-vitamin D supplemented formula fed infants
- vegetarian diets
- maternal vitamin D deficiency
- lack of sun exposure
- dark skin in sun-poor countries
- lack of outdoor time
- clothing that eliminates sun exposure
The onset and presentation of rickets depend on the aetiology and degree of deficiency. Typically, in severe cases, rickets becomes apparent in the second year of life.
The presentation is usually with skeletal changes (see below) and bone pain.
Results from abnormality or deficiency in one or more of 1:
- 1,25-dihydroxyvitamin D
- phosphorus, e.g. from X-linked hypophosphataemia
- alkaline phosphatase
- body pH
As a consequence of this imbalance, the ratio of mineralised to non-mineralised osteoid is abnormal (with an excess of the non-mineralised osteoid), and bone strength is reduced.
In the growing skeleton, the deficiency of normal mineralisation is most evident at metaphyseal zones of provisional calcification where there is an excess of non-mineralised osteoid resulting in growth plate widening with metaphysis flares out and appears frayed.
It is not surprising that these features are most prominent at the growth plates where growth is greatest:
- knee: distal femur, proximal tibia
- wrist: especially the ulna 1
- anterior rib ends: rachitic rosary
It is important to remember that even bones that appear mineralised are weak and result in bowing, most commonly seen in the lower limbs once the child is walking. The legs bow outwards with variable deformity of the hips (both coxa vara and coxa valga are seen 1). The lower ribs may also be drawn inwards inferiorly by the attachment of the diaphragm (Harrison's sulcus).
Treatment and prognosis
Treatment requires correction of the metabolic imbalance. Only rarely is orthopaedic surgical intervention necessary to correct skeletal deformities.
The differential for leg bowing in children includes 2:
- developmental or congenital bowing
- Blount disease
- osteogenesis imperfecta
- many others that are not usually a consideration (see leg bowing in children)
The differential for widening of the growth plate includes:
- Schmid-type metaphyseal chondrodysplasia
- hypovitaminosis C (scurvy)
- delayed maturation due to illness
- endocrine disturbances
The differential for flaring of the metaphysis includes:
- 1. Schulthess GK, Zollikofer CL. Musculoskeletal diseases, diagnostic imaging and interventional techniques. Springer Verlag. (2005) ISBN:8847003180. Read it at Google Books - Find it at Amazon
- 2. Cheema JI, Grissom LE, Harcke HT. Radiographic characteristics of lower-extremity bowing in children. Radiographics. 23 (4): 871-80. doi:10.1148/rg.234025149 - Pubmed citation
- 3. Reeder MM, Felson B. Reeder and Felson's gamuts in radiology, comprehensive lists of roentgen differential diagnosis. Springer Verlag. (2003) ISBN:0387955887. Read it at Google Books - Find it at Amazon
- 4. Garfunkel LC, Kaczorowski J, Christy C. Mosby's pediatric clinical advisor, instant diagnosis and treatment. Mosby Inc. (2002) ISBN:0323010490. Read it at Google Books - Find it at Amazon
- 5. Musculoskeletal Imaging: The Requisites, 4e (Requisites in Radiology). Saunders. ISBN:0323081770. Read it at Google Books - Find it at Amazon
Metabolic bone disease
- bone mineralisation
- osteosclerosis (differential diagnosis / mnemonic)
- pituitary gland-related
- thyroid gland-related