Haemochromatosis Arthropathy

Haemochromatosis arthropathy is the joint disease caused by hereditary (primary) haemochromatosis, an inherited disorder of iron metabolism in which excessive intestinal iron absorption leads to progressive tissue iron overload. Iron accumulates in many organs - liver, pancreas, heart, pituitary, skin - and also in synovium and cartilage, where it produces a distinctive degenerative arthropathy. The arthropathy is clinically important to orthopaedic surgeons because it is frequently the presenting feature, mimics osteoarthritis in unusual joints, and is largely irreversible even when the underlying iron overload is treated.

Genetics and biochemistry:

• Most cases are due to homozygosity for the C282Y mutation in the HFE gene (chromosome 6); compound heterozygosity (C282Y/H63D) is a less penetrant cause
• HFE dysfunction reduces hepcidin, the master iron-regulatory hormone, leading to unrestrained ferroportin-mediated iron export and absorption
• Autosomal recessive inheritance; clinical penetrance is incomplete and modified by sex, blood loss and alcohol

Epidemiology:

• One of the commonest inherited disorders in people of Northern European ancestry; C282Y homozygosity occurs in roughly 1 in 200 to 1 in 400 of this population
• Much rarer in South American, African and East Asian populations, where the HFE C282Y mutation is uncommon - the diagnostic algorithm differs there
• Joint pain is reported by around 70-75% of patients with iron overload and often precedes the diagnosis by years
• Men present earlier and more severely than women, who are partially protected by menstrual and pregnancy blood loss

The arthropathy results from chronic iron deposition in joint tissues. Unlike gout or CPPD, the dominant mechanism appears to be iron-driven damage to bone and cartilage cells rather than a single crystal trigger, although crystal disease frequently coexists.

Iron handling and the joint

Systemic iron loading:

• Loss of HFE function lowers hepcidin, so enterocytes and macrophages export iron unchecked via ferroportin
• Transferrin becomes saturated and non-transferrin-bound iron circulates, depositing in parenchymal tissues including synovium and cartilage
• Iron is visible histologically as haemosiderin in synovial lining cells and chondrocytes, and as low-signal "blooming" foci on T2*-weighted MRI

How iron damages the joint

Direct cellular toxicity:

• Excess intracellular iron catalyses reactive oxygen species (Fenton chemistry), causing oxidative stress
• In chondrocytes, iron exposure increases catabolic enzymes (matrix metalloproteinases such as MMP3 and MMP13), reduces extracellular matrix and aggrecan production, and pushes cells toward a hypertrophic, osteoarthritis-like phenotype
• Iron-loaded synovium becomes inflamed and contributes to cartilage breakdown

Bone-centred mechanisms (shared with CPPD):

• Iron overload reduces osteoblast alkaline phosphatase activity and increases osteoclastogenesis, producing generalised bone loss and impaired joint repair
• These abnormalities in bone turnover and damage/repair are strikingly similar to those seen in CPPD, which may explain why the two diseases overlap and why haemochromatosis arthropathy can occur even without demonstrable CPP crystals

Link with calcium pyrophosphate deposition

• Haemochromatosis is one of the classic metabolic associations of CPPD
• Iron may inhibit pyrophosphatases or otherwise favour calcium pyrophosphate crystal formation, and shared effects on bone cells link the two
• Chondrocalcinosis is a common radiographic finding, and acute pseudogout attacks can occur

Small-joint disease (the classic pattern)

• Insidious pain, stiffness and bony swelling of the 2nd and 3rd metacarpophalangeal joints
• Often bilateral and symmetrical; reduced grip and difficulty making a fist
• Wrists are also commonly involved
• The pattern resembles osteoarthritis but in joints that primary OA usually spares

Large-joint disease

• Hips, knees, ankles and shoulders may develop a destructive OA-like arthropathy
• Ankle involvement is increasingly recognised and can be a major source of disability
• Large-joint disease is a frequent reason for joint replacement, sometimes at a relatively young age

Acute presentations

• Acute pseudogout (acute CPP crystal arthritis) from coexisting chondrocalcinosis - a hot, swollen joint (often knee or wrist)
• Acute monoarthritis must always be distinguished from septic arthritis

Associated systemic features (the diagnostic context)

• Liver: hepatomegaly, deranged liver function, cirrhosis, hepatocellular carcinoma
• Pancreas: diabetes mellitus ("bronze diabetes")
• Skin: bronze or slate-grey pigmentation
• Heart: cardiomyopathy, arrhythmia
• Endocrine/gonadal: hypogonadism, impotence, fatigue
• Haematology: a high-normal or raised mean corpuscular volume (MCV) is associated with the presence of arthritis in haemochromatosis

Physical examination

Inspection:

• Bony enlargement of the 2nd/3rd MCP joints; squared knuckles
• Effusions in larger joints during acute crystal attacks
• Look for skin pigmentation and stigmata of chronic liver disease

Palpation and movement:

• Hard, bony swelling rather than boggy synovitis (synovitis is the minority)
• Reduced range and grip; crepitus in established large-joint OA

Biochemical screening for iron overload

First-line iron studies:

• Transferrin saturation - the most useful initial screening test; a fasting value above approximately 45% in women or 50% in men is suggestive
• Serum ferritin - reflects iron stores but is an acute-phase reactant, so interpret with transferrin saturation

Confirmation:

• HFE genotyping - C282Y homozygosity (or compound C282Y/H63D heterozygosity) confirms hereditary haemochromatosis in a patient with biochemical iron overload
• In populations where C282Y is rare, or with non-HFE genotypes, MRI quantification of hepatic iron or liver biopsy is used to demonstrate iron overload
• Assess end-organ damage: liver function, fasting glucose/HbA1c, and fibrosis staging

Synovial fluid (if acute hot joint)

• Send for crystals and culture - to identify coexisting CPP crystals (rhomboid, positively birefringent) and to exclude sepsis
• Crystals never exclude infection; treat as septic if in doubt

Imaging

Plain radiographs - the key examination:

• Squared metacarpal heads with hook-shaped osteophytes on the radial aspect of the 2nd and 3rd metacarpal heads (near-pathognomonic)
• Subchondral cysts and uniform joint space narrowing
• Chondrocalcinosis in wrists, knees, symphysis pubis and other fibrocartilage
• Large joints: OA-like changes (sometimes severe, sometimes at unusually young age)

MRI:

• T2*-weighted ("gradient-echo") sequences show low-signal blooming from iron/haemosiderin in synovium
• Demonstrates associated cartilage loss, meniscal and ligamentous changes

Differential diagnosis of the small-joint arthropathy

The exam test is to recognise that "osteoarthritis" of the MCP joints is not ordinary OA.

Indications for Surgery

1. End-stage large-joint OA (hip, knee, ankle, shoulder) with pain and functional loss refractory to conservative care
2. Disabling MCP/hand disease - selected cases may benefit from hand surgery, though small-joint reconstruction is less commonly required
3. Mechanical derangement - e.g. meniscal pathology or loose bodies

Disease Complications

• Progressive joint destruction despite iron-depletion therapy
• Acute pseudogout flares from coexisting CPPD
• Generalised bone loss / osteoporosis related to iron effects on bone cells and hypogonadism
• Systemic morbidity: cirrhosis, hepatocellular carcinoma, diabetes, cardiomyopathy, hypogonadism - all relevant to perioperative risk

Surgical Complications

• Increased anaesthetic and bleeding risk in patients with significant liver disease
• Impaired glycaemic control and infection risk in those with diabetes
• Standard arthroplasty risks; crystal flare can occur perioperatively
• Continued symptoms in other joints as the systemic arthropathy progresses

Haemochromatosis arthropathy remains incompletely understood, which makes it good higher-order viva material.

• Exact mechanism of joint damage: whether iron acts mainly through direct chondrocyte toxicity, through disordered bone remodelling, or via promotion of CPP crystals is still debated; animal models do not always reproduce direct cartilage damage.
• Relationship with CPPD: the two diseases overlap clinically and share bone-centred pathways, but it is unclear how much of the arthropathy is "iron arthropathy" versus secondary CPPD.
• No joint-specific therapy: nothing reliably removes iron from cartilage or reverses the arthropathy; iron chelation has not been shown to treat the established joint disease.
• Whom and when to screen: the yield of iron studies in isolated hand OA versus the value of early detection (to protect the liver and heart) influences screening thresholds, which vary between guidelines.
• Optimal timing of large-joint surgery in patients who may also have liver disease and diabetes is individualised, with limited high-level evidence.

Haemochromatosis arthropathy is a global disease wherever iron overload occurs, but the genetic background and diagnostic algorithm differ by population. International guidance agrees on two principles: detect and treat iron overload early to protect the liver and heart, and manage the joints on their own merits because the arthropathy is largely irreversible.

Global epidemiology

• HFE C282Y homozygosity is common in people of Northern European ancestry (roughly 1 in 200 to 1 in 400) and is the dominant cause there.
• In South American, African and East Asian populations the C282Y mutation is rare, so diagnosis relies more on biochemical iron overload plus MRI-quantified hepatic iron or biopsy and consideration of non-HFE genotypes.
• Joint pain affects around 70-75% of patients with iron overload and frequently precedes diagnosis by years.

Side-by-side guidance

Registry and arthroplasty evidence

• Large arthroplasty registries (NJR, AOANJRR, AJRR, Swedish/Norwegian) do not list haemochromatosis as a distinct indication, but cohort data show joint replacement is common (about 16% of patients) with generally good results, driven by severe large-joint OA.
• Implication: standard implant and bearing selection applies; haemochromatosis changes perioperative medical optimisation, not prosthesis choice.

High- vs limited-resource practice variation

• Well-resourced settings: HFE genotyping, MRI iron quantification and structured venesection programmes are readily available; T2*-weighted MRI can demonstrate joint iron.
• Limited-resource settings: diagnosis often rests on transferrin saturation, ferritin and plain radiographs (the hook-osteophyte pattern); venesection remains low-cost and effective, while chelation is reserved for those who cannot be venesected.
• Everywhere: recognise the MCP/chondrocalcinosis pattern, screen for iron overload, treat systemic disease early, and screen first-degree relatives.