rickets and osteomalacia-

7/28/2019 rickets and osteomalacia-

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A 40 year old male , a known case of epilepsy presentedwith a 4-month history of generalized muscular

discomfort, particularly in her shoulders, present at rest.The symptoms were not worse in the morning and therewere nonspecific relieving factors. Her weight wasstable.

On examination she exhibited mild proximal weakness

in both arms and legs, but no muscle tenderness and thereflexes were preserved. There was no temporal artery orscalp tenderness, and the remainder of the examinationwas unremarkable.


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Subsequent investigation demonstratedhaemoglobin 10.9 g/dL,ESR 16mm/h, plasma

glucose (postprandial) 7.6mmol/L, glycatedhaemoglobin 5.6%, plasma urea andelectrolyteswithin normal limits,

plasma calcium 7.4mg/dl(N 8.5-10.5),phosphate

2.5mg/dl(N 4.5-6.5) and plasma alkalinephosphatase 198IU/L (normal


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What is the most likely explanation for her symptoms

and what other causes should be considered?


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This patient's presentation with myalgia associatedwith a combination of mild hypocalcaemia,hypophosphataemia and elevation of alkalinephosphatase is strongly suggestive of Osteomalasia.


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Rickets and osteomalacia are conditionscharacterized by pathological defects in bone matrix

mineralization. Rickets refers specifically toosteomalacia, where the defect occurs in growingbone.

The aetiological factors are diverse, but the end

result is an increased quantity of unmineralizedbone matrix (osteoid).

RICKETS AND

OSTEOMALACIA


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RICKETS &

OSTEOMALACIA

Def.: reduction in bone mineralization !


7/19

The conditions may arise in three distinct

situations:

Deficiency or abnormal metabolism of vitamin D

Phosphate depletion

Chronic metabolic acidosis.

aetiology of

osteomalacia


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Vitamin D deficiency is numerically by far themostimportant cause of osteomalacia (or rickets): itleads to acombined deficiency of calcium andphosphorus. There is intestinal malabsorption of

calcium and, to a lesser extent Phosphorus. Secondaryhyperparathyroidism results from the fall in plasmacalcium, and the ensuing phosphaturia accelerates thephosphate deficiency.


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Lack of vitamin D is often due to a combination of poor exposure to

sunlight and dietary deficiency. The elderly are particularly at risk. The reason for this is multifactorial and incompletely understood, but

dietary deficiency of vitamin D and calcium, together with binding ofcalcium by the phytate contained in chapati flour, may contribute. Inaddition,deeply pigmented skin generates less vitamin D3 inresponse to a given amount of ultraviolet exposure, an dthis may bedisadvantageous in temperate climates.

Vitamin D deficiency may complicate fat malabsorption from anycause.

Finally, calcium deficiency enhances the rate of degradation of 25(OH)D

in the liver, further exac-erbating the shortage of vitamin D and itsmetabolites. abnormality of the 1,25(OH)2D receptor in target tissues(vitamin D-dependent rickets type II).


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Phosphate depletion is a less common cause ofrickets than deficiency or altered metabolism ofvitamin D. It arises as a result of a reduced maximalcapacity for renal tubular phosphate reabsorption. This

may either be inherited as an X-linked recessivecharacteristic (vitamin D-resistant rickets, X-linkedhypophosphataemia) or occur aspart of Fanconi'ssyndrome - a more generalized hereditary oracquired renal tubular defect typified by

aminoaciduria and glycosuria (p. 1057).Rarely, excessive ingestion of antacids may restrict

intestinal phosphate absorption to the point whereclinically important phos-phate depletion, and evenosteomalacia or rickets, may appear.


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Chronic metabolic acidosis, usually resulting from

renal tubular disorders, may lead to rickets orosteomalacia. The bone lesions usually healsatisfactorily following treatment to correct theacidosis.


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In children, failure of bone mineralization gives

rise to classic bone deformities, which include

widening of the metaphyses, prominence ofcostochondral junctions (socalled 'rickety rosary'),and varus or valgus abnormalities of the knee

joints. The bones are painful and statural growthis reduced.

In adults, bone pain and tenderness are the mostprominent features. A characteristic proximalmyopathy may develop, and is more common incases due to vitamin D deficiency.

Clinical features


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Biochemical In osteomalacia due to deficiency or abnormal metabolismof vitamin D, investigations typically demonstrate a low

normal plasma calcium (leading to secondary hyper- parathyroidism), a low plasma phosphate due to phosphaturia as a result of increased PTH secretion, and a raisedalkaline phosphatase indicating increased numbers of osteoblasts . Vitamin D deficiency may be confirmed by measurement of 25-

hydroxyvitamin D in plasma. X-linked hypophosphataemia (vitamin D-resistantrickets), on the other

hand, is characterized by normocal-caemia, hypophosphataemia, andlittle or no alteration in

plasma alkaline phosphatase level.

Investigation


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RICKETS, OSTEOMALACIA

XRAY FINDINGS:

RICKETS

Thickening and widening ofphyses,

Cupping of metaphysis,

Wide metaphysis,

Bowing of diaphysis,

Blurred trabeculae.
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RICKETS, OSTEOMALACIA

XRAY FINDINGS:

OSTEOMALACIA

Loosers zones - incomplete

stress # with healing lackingcalcium, on compressionside of long bones.

Codfish vertebrae due topressure of discs

Trefoil pelvis, due toindentation of acetabulaestress #s
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Occasionally a bone biopsy may be needed(following

double tetracycline labelling) to confirm a diagnosisof

osteomalacia whhen biochemical investigations areequivocal. This is particularly the case when

seeking possible treatable factors in elderly patientswith decreased bone density.

Histological


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Dietary vitamin D deficiency is treated by oral replace-

ment of vitamins D2 or D3 in physiological quantities(500-1000 units/day). This can conveniently be given as combinedcalcium with vitamin D tablets.Alternatively,a single i.m. does of 150 000IU of D2 in oil iseffective prophylaxis and treatment for at least 6 months. Thepossibility of intestinal malabsorption should be borne in mind,and appropriate investigation initiated if necessary.

Osteomalacia associated with anticonvulsant therapyrequires higher doses of vitamin D (3000-6000units/day)unless a change in anticonvulsant is clinicallyfeasible.

Management


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Treatment of X-linked hypophosphataemia is

generallyunsatisfactory. The logical treatment is with

oral phosphatesupplements, but the doses neededare large and they maybe poorly tolerated because ofgastrointestinal side-effects.Oral phosphate worksbetter when combined with phar-macologicaldoses of vitamin D, or (and probably best)

incombination with 1,25(OH)2D3. When1,25(OH)2D3 orlaOHD3 is given, great care mustbe taken to adjust the dose against the serumcalcium, as hypercalcaemia may easily be induced.

Management

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rickets and osteomalacia-