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Disorders of bone mineralisation Flashcards

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1
Q

What are the signs and symptoms of hypercalcaemia?

A
  • Asymptomatic
  • Bones
    • excessive bone resorption
  • Stones
    • renal
    • polyuria/polydipisa, dehdyration, kidney stones
  • Groans
    • intestinal
    • constipation, anorexia, nausea and vomiting
  • Psychic moans
    • cns
    • confusion/ stupor
  • other symptoms- stiff joints/myopathy/hypertension
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2
Q

Describe the causes of hypercalcaemia?

A
  • Primary hyperparathyroidism
  • Malignancy
  • Familial
    • Multiple endocrine neoplasia ( MEN) I & II
      • ​MEN 1- pancreatic/pituitary tumours
      • Men 2- thyroid medullary caricinoma of thyroid and bilateral phaeochromoctyomas
    • familal hypocalciuric hypercalcaemia
      • ​defect in calcium-sensing receptor -> poor renal clearance
  • Endocrine
    • Hyperthyroidisim
    • Addison’s disease
  • Exogenous
    • Vitamin D excess
    • steriod admininstration
  • Metabolic
    • milk alkali syndrome
  • Granulomas
    • sarcoidosis - generating 1,25 (OH)2 D3
  • Tertiary hyperparathryroidism
    • ​after prolonged primary hyperparathyroidism, where the glands act autonomously secreting excess PTH-> hypercalcaemia
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3
Q

What is the aetiology of primary hyperparathyroidism?

A
  • Solitary parathyroid adenoma 80%
  • parathyroid hyperplasia 15%
  • Multiple parathyroid adenomas 4%
  • parathyroid carcinoma 1%
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4
Q

What is seen in primary hyperparathyroidism?

A
  • Plasma calcium high
  • Plasma phosphate is low ( increased renal excretion)
  • -> bone reabsorption & inadequate repair ( lack of phosphate)
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5
Q

What is seen on ecg with primary hyperparathyroidism?

A
  • Decreased QT interval
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6
Q

What is the blood/urine picture of primary hyperparathyroidism?

A
  • High calcium
  • High PTH
  • Low phosphate

Urine

  • high phosphate
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7
Q

What is seen on xrays with primary hyperparathyroidism?

A
  • osteopenia
  • predilection for cortical bone
  • osteitis fibrosa/ brown tumours
  • subperiosteal resorption
    • radial borders of proximal phalanges and tufts of distal phalanges
  • Pepper pot skull
  • chondrocalcinosis and metastatic calcification in soft tissues
  • loss of lamina dura around teeth is specific
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8
Q

What tumours cause hypercalcaemia?

A
  • Those that secrete PTH- related protein
  • esp Squamous lung carcinoma
  • solid tunours with bony mets
    • ​breast, kidney, thyroid , prostate
    • cytokine related effects IL1, IL6 and TNF-alpha via activation of osteoclasts
  • Haematological malignancues
    • clonal plasma cell resorb bone in mutliple myeloma via cytokine related effects
    • lymphomas synthesise 1,25 (OH)2 D3
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9
Q

What is the tx of hypercalcaemia?

A
  • tx underlying cause
  • rehydration with normal saline ( saline diuresis)
  • Loop diuretics with or without dialysis ( severe cases)
  • Specific pharmacotherapy
  • Bisphosphonates
  • Chemotherapy in malignancy e.g. Mithramycin
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10
Q

What are the symptoms of hypocalcaemia?

A
  • Neuromuscular irritability
    • Tetany
    • seizures
    • Chvostek’s sign
      • tapping over parotid gland in region of facial nerve -> muscle twitches
    • Trosseau’s sign
      • carpopedal spasm if brachial artery occluded with blood- pressure cuff
    • Depression
    • ECG- prolonged QT
  • ​Chronic
    • Cateracts
    • Fungal nail infections
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11
Q

What are the aetiology of hypocalcaemia?

A

Low PTH and low vitamin D => hypocalcaemia

  • Hypoparathyroidism
  • Pseudo-hypoparathyroidism
  • Renal osteodystrophy
  • Osteomalacia/Rickets
  • Hypophosphatasia
  • Oncogenic osteomalacia
    • non ossifying fibroma
    • neurofibromatosis
    • fibrous dysplasia
    • haemangiopericytomas
  • Anticonvulsant medication- phenytoin
  • high does bisphosphonates
  • heavy metal over dose
  • chronic alcoholism
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12
Q

What are the causes of hypoparathyroidism?

A
  • Usually post surgery- thyroidectomy
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13
Q

What are the effects on blood test in hypoparathyroidism?

A
  • Decreased PTH-> low plasma Calcium
  • High plasma phosphate
  • Alkaline phosphatase normal
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14
Q

What are the symptoms of hypoparathyroidism?

A
  • Those for hypocalcaemia
    • tetany
    • seziures
    • chvostek’s and trosseay sign
    • depression
    • longer QT interval
  • Vitalgo and hair loss
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15
Q

What is the tx of hypoparathyroidism?

A
  • Vitamin D analogues e.g. alfracalcidol
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16
Q

What is the aetiology of peusdo- hypoparathyroidism?

A
  • Rare inherited disorder due to failure of target cells response to PTH
  • pathology due to
    • PTH receptor abnormality
    • Signalling abnormality e.g. cyclic AMP defect, G protein abnormality
    • Lack of necessary cofactors e.g. magnesium
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17
Q

Name one type of pseudo- hypoparathyroidism?

Study These Flashcards
A
  • Albright hereditary osteodystrophy
    • BORESS
      Brachyldactyly- short 1st.4th/5th MT and MC
    • Obesity
    • Reduced Intelligence
    • exostoses
    • Skull xray show basal ganglia calcification
    • subcutaneous ossification
18
Q

what are the effects of pseudo-hypoparathyroidism/

Study These Flashcards
A
  • Increased PTH ( can produce it but target cells don’t respond to it)
  • Low calcium
  • Normal or increased Alkaline phosphatase
19
Q

What is renal osteodystrophy?

Study These Flashcards
A
  • A group of disorders of bone mineral metabolism seen in chronic renal failure
  • High turnover renal bone disease
  • low turnover renal bone disease
20
Q

what is seen in high turnover renal bone disease?

Study These Flashcards
A
  • uraemia
  • phosphate retention
21
Q

how does high turnover renal bone disease lead to hypocalcaemia?

Study These Flashcards
A
  • high plasma phosphate ->
    • impaire synthesis of 1,25 (OH)2 vitamin D3 by inhibiting renal 1-alpha hydroxylase ( note that synthesis of renal vitamin D metabolite is also directly impaired by tubular damage in renal failure)
    • direct lowering of calcium which stimulates PTH
    • direct stimulation of PTH secretion
  • Low serum calcium -> secondary Hyperparathyroidism and ultimately hyperplasia of the chief cells of the parathyroid gland and tertiary hyperparathyroidism
  • as renal function deteroriates acidosis exacerbates the negative calcium balance
22
Q

What is seen in low turnover renla bone disease?

Study These Flashcards
A
  • Slowed bone formation and turnover- adynamic response
  • Slowed mineralisation- osteomalacia
  • Alumium deposits
    • impaired renal excretion
    • inhibtion of proliferation and differentiation of Osteoblasts
    • Inhibition of PTH release from pararthyroid gland
  • No secondary hyperparathyroidism
23
Q

what are the effects of renal osteodystrophy?

Study These Flashcards
A
  • Hypocalaemia
    • rickets/osteomalacia
  • SUFE
  • Secondary hyperparathyroidism
    • osteitis fibrosa et cystica ( bone marrow replacement by fibrous tissue)
    • osteosclerosis (20% cases)
      • from 2ary hyperparathyrodism
      • increased OB activity
      • lucent and dense bands in spine- rugger-jersey spine
    • metastatic calcification
      • ca and phosphate solubility may be affected -> ectopic calcifications in the conjuctivia, blood vessels, skin and periacrticular vessels
  • Amyloidosis
    • as a result of beta-1 microglobulin from chronic diaylsis
    • clinical effects= pathological fx ( amyloid deposits) arthropathy, carpal tunnel syndrome
    • dx made on histology woth Congo red stain
24
Q

What are the laboratory changes in renal osteodystrophy?

Study These Flashcards
A
  • Increased urea and creatinine
  • Increased phosphate
  • Low/ normal calcium
  • raised alkaline phosphatase ( osteoblasts)
  • High PTH ( low calcium stim/ direct stim of PTH)
25
How is the dx of renal osteodystrophy made?
* Tetracycline labelled bone biopsy
26
What is the tx of renal osteodystrophy?
* Mainly medical * _adjust serum phosphate to normal_ * **reduce dietary intake** ( less eggs/milk/cheese) * **Phosphate binders** - calcium carbonate * _Adjust calcium to normal_ * **Increase calcium absorption** with **1,25 (OH)2 D3** * Calcium supplementation * _Supress secondary hyperparathryroidism_ * **1,25 (OH)2 D3** or may reiquire **parathyroidectomy** * **Chleate bone aluminium in cases of aluminium retention ( with desferrioxamine)** * **Manage chronic renal failure with dialysis of renal transplant**
27
Define osteomalacia?
* **Is a deficient or impaired mineralisation of the bone matrix**
28
What is Rickets?
* Is the **juvenile form** of osteomalacia with **impaired mineralisation of cartilage matrix** ( chondroid) affecting the **physis** in the **zone of provisional calcification**
29
what is the aetiology of rickets/osteomalacia?
1. _Dietary deficiency_ * **Calcium or vitamin D deficiency** * **Dietary chelators** ( phytates in chapattis, oxalates in spinach) * **Phosphorous deficiency** ( aluminium containing _antacid abuse_) 2. _Gastrointestinal malabsorption_ * **post- gastrectomy** * **biliary disease** * **intestinal defects** * **short bowel syndrome, coeliac disease, crohn's disease** 3. **_Renal tubular defects ( loss of phosphate)_** * hypophosphataemic vitamin d resistant rickets * mutliple renal tubular defects-\> aminoaciduria ( fanconi syndrome) * Renal tubular acidosis 4. **_Hereditary vitamin D dependent rickets_** 5. **_Hypophosphatasia_** 6. **_Oncongenic osteomalacia_** 1. _​fibrous dysplasia, non ossifiying fibroma_ 7. **_​anticonvulsants- phenytoin_** 8. **_high dose bisphosphonates_** 9. **_heavy metal overdose_** 10. **_chronic alcoholism_**
30
what is hypophosphataemic vitamin D resistant rickets/osteomalacia?
* **Most common form of rickets** * **X linked dominant ** * mutation in P-EX gene * _Impaired renal tubular reabsorption of phosphate_ * charactertistic deformity * **bilateral symmetrical anterolateral femoral and tibial bowing​** * ​normal GFR but reduced vitamin D response * xrays resemble anklosing spondylitis with ligamentous calfication and ossification ( enthesiopathy)
31
what is the tx of hypophosphataemic vitamin D resistant rickets/osteomalacia?
* **Phosphate replacement** * **high does vitamin D3** necessary
32
What is the inherited form of multiple renal tubular defects-\> aminoaciduria?
* Cystinosis
33
What is the acquired form of mutliple renal tubular defects-\> aminoaciduria?
* **mutliple myeloma**
34
What is renal tubular acidosis?
* proximal ( bicarbonate wasting) * distal ( H+ gradient effect) * acquired- ureterosigmoid anastomosis
35
What is hereditary vitamin D -Dependent rickets?
* V rare * clinically severe rickets with alopecia totalis, epidermal cysts and oligodontia ( missing 5 or more adult teeth) * _inherited defect of 25 (OH)2 vitamin D3 hydroxylation_
36
what is the difference between type 1 and type 2 hereditary vitamin D -Dependent rickets?
* _Type 1_ * **renal 1 alpha hydroxylasse deficiency** * autosomal recessive * chromosome 12q14 * _Type 2_ * **end organ insensitivity to 1,25 (OH)2 vitamin D3** * abnormality in nuclear receptor
37
What is hypophosphatasia?
* **Autosomal recessive disorder of phosphate synthesis** * due to **low levels of alkaline phosphatase** * **_increased urine phosphoethanolamine i_**s diagnostic * trend towards distinguishing hypophosphatasia as a clinical entitiy separate from osteomalacia
38
What is generally seen in rickets?
* **Retarded bone growth and short stature** * Pathological fx * **Looser's zones** on compression side ( see image) * **symptoms of hypocalcaemia** * **Proximal myopathy** * vitamin D receptors present in skeletal muscle
39
What is seen in rickets looking head to toe?
* Delayed Frontal closure and frontal parietal bossing * Dental disease * enlarged of costochondral junction - **rachitic rosary** * **Harrison sulcus** - indentation of lower ribs at diaphragm insertion * centrally depressed 'cod fish vertebra' dorsal kyphosis ( cat back) * bowing of knees - sabre shin * waddling gait
40
What is seen on bloods from a child with rickets?
* **Increased PTH** * **Low Calcium** * **Low phosphate** * **Low vitamin D levels**
41
What is seen on xrays of rickets?
* Physeal increase in height and width- continues to growth but can't mineralise * metaphyseal cupping, flaring and jagged appearance * small ossified nuclei * coxa vara * flattening of skull
42
What is seen on plain xrays of osteomalacia?
* Looser's zones- stress fx on concave border of long bones * Milkman pseudo-fx on compressio side of long bones ( fx healed but not mineralised) * biconcave vertebral bodies -\> severe kyphosis * thin cortices, indistinct, fuzzy trabeculae * triradiate pelvis * signs of hyperparathyroidism

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