FFinalistSouthampton · 2027
Musculoskeletal
AKT · Musculoskeletal/Crystal & degenerativelow yield

Pseudogout (CPPD)

Calcium pyrophosphate dihydrate crystal deposition → acute and chronic arthritis

Overview

Acute or chronic arthritis from calcium pyrophosphate dihydrate (CPPD) crystal deposition, typically in larger joints (knee, wrist) of older people. Aspiration shows positively birefringent rhomboid crystals; X-ray shows chondrocalcinosis (cartilage calcification). It can be precipitated by intercurrent illness and is associated with metabolic conditions (haemochromatosis, hyperparathyroidism).

Recognise

  • Acute hot, swollen joint — most often KNEE or wrist — in an older patient; may be precipitated by illness/surgery
  • Chondrocalcinosis (linear cartilage calcification) on X-ray; chronic CPPD can resemble osteoarthritis
  • Look for an underlying metabolic cause if young/florid: haemochromatosis, hyperparathyroidism, hypomagnesaemia, hypophosphatasia

Red flags

  • Exclude SEPTIC arthritis in any acute hot joint by aspiration
  • Florid/young-onset disease → screen for haemochromatosis/hyperparathyroidism

Differentials & how to tell them apart

Goutnegatively birefringent needle crystals; first MTP; hyperuricaemia
Septic arthritisorganisms on aspirate — exclude first
Osteoarthritischronic CPPD overlaps OA but has chondrocalcinosis
Chondrocalcinosis — calcification of knee cartilage (X-ray)

Chondrocalcinosis — calcification of knee cartilage (X-ray)

Taokinesis / CC0 — Wikimedia Commons

Investigations

Joint aspiration and polarised microscopy (POSITIVELY birefringent rhomboid CPPD crystals; exclude sepsis); X-ray (chondrocalcinosis); ferritin/Ca/PTH/Mg in young or florid disease.

Management

Aspirate to exclude sepsis → NSAID/colchicine/intra-articular steroid

  1. 1Aspirate the joint to confirm positively birefringent rhomboid crystals and exclude septic arthritis. Treat the acute attack with an NSAID, colchicine or a corticosteroid (often intra-articular).Gate: Young or florid/recurrent CPPD → investigate for an underlying metabolic cause (haemochromatosis, hyperparathyroidism, hypomagnesaemia).
  2. 2Manage recurrent attacks symptomatically (no urate-equivalent therapy) and treat any identified metabolic disorder.
NSAID (+PPI), colchicine, or corticosteroid (intra-articular/oral) — as for acute gout — no equivalent of urate-lowering therapy exists
Joint aspiration — both diagnostic and therapeutic for a tense effusion
Treat any underlying metabolic disorder — haemochromatosis/hyperparathyroidism
Rest and supportive care — acute attacks are usually self-limiting

Key points

Acute hot KNEE/wrist in an older patient + positively birefringent rhomboid crystals + chondrocalcinosis on X-ray = pseudogout (CPPD). Exclude sepsis; treat like acute gout. Young/florid disease → screen for haemochromatosis and hyperparathyroidism.

Monitor & prognosis

Attack frequency; metabolic screen results.

Acute attacks self-limit; chronic CPPD causes a degenerative arthropathy.

Source: NICE CKS (CPPD/pseudogout)