Crystal deposition diseases: out of sight, out of mind.
- Geraldine M McCarthy
- Current opinion in rheumatology
There are a variety of crystals that may be associated with joint and soft-tissue problems, due to their deposition in and around joints1(Table 1). This review will focus primarily on the potential problems associated with monosodium urate monohydrate (MSU) crystal deposition and the calcium crystal associated problems. where they are associated with degenerative changes. The crystals may provoke an acute attack of synovitisreferred to as pseudo-gout. The deposits are often visible as a fine layer of calcification overlying the menisci and articular cartilage of the kneetermed chondrocalcinosis; and BCP crystals can also cause acute inflammatory attacks of arthritis, usually around the shoulder, referred to as calcific periarthritis2. I. Calcium pyrophosphate dihydrate (CPPD) crystal associated arthropathies: CPPD crystal deposition disease is usually idiopathic and presents as sporadic episodes in the majority of patients. There are rare familial forms of the disease and an association with some metabolic disorderssuch as hyperparathyroidism, haemochromatosis, hypophosphatasia, Wilson’s disease, ochronosis, hypo-calciuric hypercalcaemia (and perhaps other hypercalcaemic states), diabetes mellitus and hypomagnasaemiahas been documented3,5. Treatment of osteoarthritis (OA) of the knee with intra-articular injections of hyaluronic acid preparations (such as Hylan GF-20) has also been associated with triggering of an acute attack of pseudo-gout4. Familial CPPD deposition disease generally may present in one of two ways3: A rather benign, early onset (< 50 yrs), usually acute presentation, having a polyarticular distribution involving the knee, wrist, shoulder, elbow, hip or ankle and recurrent episodes of crystal-positive acute pseudo-gout and chondrocalcinosis.The second a more chronic arthropathy, with a late onset (> 50 yrs), destructive oligo/ mono-arthropathy, affecting the knees, wrists, shoulders or hips. Thus CPPD crystal associated disease is clinically heterogeneous and may cause both an acute or chronic arthritis. Some of the recognised clinical patterns of CPPD deposition disease are5: Pseudogout is the most common form (also called CPPD disease type A) and presents as acute episodes of synovitis at a single joint, most often at the knee. More common in men, the ‘attack’ typically lasts from a few days to 3-4 weeks and is characterised by acute pain, swelling and warmth at the affected joint, often indistinguishable from gout. X-ray of the knee may reveal typical calcification of the meniscuschondrocalcinosis(figure 1) and the joint synovial fluid examination will reveal the typical positively birefringent CPPD crystals, on polarising light microscopy. Attacks may be precipitated by any intercurrent illness, recent surgery or trauma and rapid diuresis. Address for correspondence Dr S J Gupta, FRCP (Edin), Consultant Rheumatologist D-110, Defence Colony, New Delhi 110024. E-mail: email@example.com Table 1 Crystal Associated Arthropathies 1