CRYSTAL DEPOSITION DISEASE

This is a group condition characterised by presence of  crystals in and around joints, bursae and tendons

- Gout
- Calcium pyrophosphate dihydrate
-  Hydroxyapatite


Consequence: Crystal deposition
Remains intact and asymptomatic
Induces acute inflammatory reaction
Results in slow destruction of the affected tissue


1. Asymptomatic hyperuricaemia
2. Acute gouty arthritis
3. Intercritical gout
4.Chronic tophaceous gout
5. Miscellaneous: Gouty nephropathy





Gout:
Definition: A disease characterised by hyperuricaemia and formation of monosodium urate crystal deposition in the body.
Gouty arthritis is joint inflammation caused by MSUM crystals in synovial fluid and joints.



Disorder of purine metabolism




Uric acid is completely filtered by the glomerulus
Completely (essential) reabsorbed in the proximal tubule
Approximately 50% is seceted back into the tubule in the descending loop
Approximately 80% of that 50% is reabsorbed in the ascending loop.
Net excretion=10% of filtered load




Common in males M:F=20:1
In females after menopause
Hyperuricaemia





Monosodium urate monohydrate crystals
Recurrent acute synovitis

Two types:

Primary: 95%
Inherited disorder
over-production or under of uric acid
Secondary 5%
Acquired conditions

Myeloproliferative disorders---- overproduction
Renal failure----- under excretion

Gout:

All patients with high serum uric acid do not develop gout
Crystals are deposited in minute clumps- remain inert for years
Local trauma- disperses crystals into joint- acute inflammatory reaction
Each crystal- phagocytosed or float free in joint.

Over years urate deposits build up in joints, periarticular tissue, tendon and bursa- destroy articular cartilage and periarticular bone

MTPJ of great toe
Olecranon bursa
Pinnae of ears

Tophi varies in size <1cm to several cm.
It may ulcerate through the skin

Clinical Features

Men >30 years of age
Women after menopause
Obese, alcohol friendly

Patients on diuretics which increases tubular reabsoption of uric acid
Family history


Acute gout

Sudden severe joint pain precipitated by

- Minor trauma
- Surgery
- Minor illness
- Unaccustomed exercise
- Alcohol

More in the night
Lasts for 1-2 weeks and completely resolves

Common sites are affected
Joint hot and tender DDx: septic arthritis
Hyperuricaemia not diagnostic
Diagnosis confirmed by synovial fluid analysis for negatively birefringent urate crystals




Chronic gout

Recurrent attacks leads to increased joint stiffness and deformity

• Tophi appear over the common sites
• Large tophi may ulcerate the skin- chalky material discharged
• Renal calculi, renal parenchymal disease

Acute Gout

Only gout

Chronic gout

Tophi appear as punched out lesions (cysts) in the para-articular bone ends

Secondary osteoarthrosis

Tophaceous disease more likely to occur in patients with

• polyarticular presentation
• Serum urate level>540umol/L (>9mg/dL)
• Disease onset at younger afe (<40yrs)

Sites of tophi

- Digits of hands and feet

- Pinna of ear (classic, less common)
- Bursa around elbows and knees

- Achilles tendon

DDx:

Infection

• Cellulitis
• Septic arthritis
• Infected bursitis

Reiter's disease

• History is more protracted
• Response to NSAIDS is less

Pseudogout

• Affects larger joints
• More common in women
• Pyrophosphate dihydrate crystal deposition

Rheumatoid arthritis

• Polyarticular gout- affecting fingers
• Elbow tophi- mistake for subcutaneous nodule

Biopsy establishes the diagnosis

Investigations

Specific investigations for confirmation

- Serum uric acid

- Joint aspiration and crystal identification

To detect medical conditions associated gout or hyperuricaemia

- FBC

- Serum creatinine/ urea

- Serum blood glucose

- Fasting lipid profile

- UFEME

- 24hr urinary urate excretion

• Useful if renal calculus procen to be urate stone
• indicated if on uricosuric agent
• assess risk of stone
• help to indicate whether overproduction or underexcretion of urate
• range 2:4 mmol/24hr or 0.34- 0.67g/24hr

Skeletal Xrays

Acute gouty arthritis: Normal, soft tissue swelling

Chronic tophaceous gout: tophi erosive bone lesions (punched out lesions), joint space is preserved until late stage, pathognomonic in foot and big toe.

To detect complications

- Renal imaging

- Skeletal Xrays

Acute Stage

- Rest to the joint

- NSAIDS

- Colchicine less effective

- Aspiration to relieve tense joint

- Intra articular hydrocortisone

Treatment

Interval therapy

- Loose weight

- Reduce alcohol

- Eliminate diuretics

- Uricosuric drugs--- allopurinol

Interval therapy indicated

Acute attacks occur at frequent intervals.

Presence of tophi

WHen renal function is affected

Uricosuric drugs used if renal function is normal

Allopurinol- Xanthine Oxidase inhibitor 

    NEVER STARTED IN ACUTE STAGE

    ALWAYS COVERED BY NSAIDS/COLCHICINE AS THEY WILL OTHERWISE PRECIPITATE  AN ATTACK OF GOUT

Chronic gout

Allopurinol is the drug of choice

Ulcerative tophi may have to be evacuated.

Q, What is intercritical gout

Asymptomatic period between attacks


Q. What is urate/ gouty nephropathy

Acute urate nephropathy

Urate crystals---- renal tubules---- obstructive ARF
Dehydration, low urine pH are precipitating factors

Chronic urate nephropathy

Urate crystals--- interstitium and renal medulla----- inflammation+ surrounding fibrosis----- irreversible CRF
Renal impairment can occur in 40% of chronic gout

Urate nephrolithiasis

Stones----- flank pain/ ureteric colic/ hematuria
Urate (radioluscent) or mixed calcium oxalate and/or calcium phosphate (radio-opaque)
Contributing factors: hyperuricosuria, low urine output, acidic urine
Urinary alkalinisation (potassium citrate or NaHCO3)--- dissolution of existing stones and prevention of recurrence.