Etiology and classification
The disease is traditionally divided into two main forms depending on the cause of excessive iron accumulation:
- Primary haemochromatosis (Primary haemochromatosis). It is based on a genetic metabolic disorder. Due to a hereditary defect, the body begins to absorb excessive amounts of iron from the gastrointestinal tract, which is then deposited in internal organs and musculoskeletal structures.
- Secondary haemochromatosis (Secondary haemochromatosis). It develops as a consequence of increased external iron intake or its release in other pathologies. The main causes of the secondary form are:
- Alimentary factor (excessive dietary iron intake);
- Liver cirrhosis (cirrhosis);
- Multiple blood transfusions;
- Refractory anaemia (refractory anaemia).
Clinical presentation and diagnostics
The primary type of the disease classically manifests in men aged 40 to 60 years.
Historically, the diagnosis of haemochromatosis has been guided by the classic clinical triad, which gave the pathology its unofficial name, «bronze diabetes» (bronze diabetic):
- Pronounced skin pigmentation;
- Liver cirrhosis;
- Diabetes mellitus (pancreatic involvement).
Along with internal organ damage, joint syndrome is a crucial part of the clinical presentation. Arthropathy and concomitant chondrocalcinosis (chondrocalcinosis) are extremely frequent signs that may occur long before the advanced stage of the disease. Elevated serum ferritin levels serve as a key marker for laboratory confirmation of the diagnosis.
Specific radiological signs (Arthropathy)
The general radiological picture of the joint syndrome in haemochromatosis superficially resembles the manifestations of ordinary osteoarthritis (OA). However, haemochromatosis is characterized by a highly specific distribution pattern of changes, most vividly manifested on hand radiographs.
Key signs of hand involvement:
- Specific localization. The pathological process predominantly involves the metacarpophalangeal joints (MCP joints). Involvement of the 2nd and 3rd fingers (index and middle) is most typical.
- Sparing of other joints. Unlike many other arthropathies, the interphalangeal joints of the hands remain relatively intact in haemochromatosis.
- Pathognomonic sign. So-called hook-like osteophytes (hook-like osteophytes) form on the radial surface of the metacarpal heads. This is a crucial diagnostic marker that must be sought on targeted radiographs.
- Concomitant chondrocalcinosis. Calcification of the articular cartilage is frequently observed and is best visualized in the wrist area.
Clinical significance: If a radiologist detects a combination of hook-like osteophytes of the metacarpophalangeal joints and signs of chondrocalcinosis on a radiograph, this should serve as an absolute reason for suspicion of occult haemochromatosis.
Differential diagnosis of osteoarthropathies
When analyzing complex osteoarticular lesions, haemochromatosis is differentiated from a number of other rare pathologies that have their own unique radiological markers:
- Multicentric reticulohistiocytosis (Multicentric Reticulohistiocytosis). Unlike haemochromatosis, this pathology more frequently affects women. It manifests as erosive arthritis (erosive arthritis) and skin nodules. Radiographs visualize sharply demarcated erosions (sharply demarcated erosions), primarily in the interphalangeal joints (prior to MCP joint involvement), as well as nodular soft tissue swelling. The disease progresses to arthritis mutilans (arthritis mutilans) and may be accompanied by global periarticular osteopenia.
- Hypertrophic Pulmonary Osteoarthropathy (Hypertrophic Pulmonary Osteoarthropathy). It develops in association with bronchogenic neoplasms. It manifests as the formation of new bone tissue — radiographs of the distal tibia and fibula reveal a characteristic lamellar pattern (lamellar pattern) along the medial cortical layer. Less commonly, the distal femur is atypically involved.
Briefly: answers to topical questions
In which internal organs, besides the liver and pancreas, is iron deposited in haemochromatosis?
In haemochromatosis, besides the liver and pancreas, iron accumulates in the spleen, bone marrow, and heart.
- Spleen (spleen) — iron accumulation causes an abnormally low signal on T2-weighted images.
- Bone marrow — iron is deposited in the cells of the reticuloendothelial system.
- Heart — the infiltrative process affects the myocardium and conduction system, which can be detected by endomyocardial biopsy.
What MRI signs are characteristic of liver involvement in haemochromatosis?
Liver involvement in haemochromatosis is characterized by an abnormal decrease in the signal intensity of the parenchyma.
- T2-WI and T2* — signal drop due to the local magnetic susceptibility effect (susceptibility effect). The most sensitive method is T2* gradient echo.
- T1-WI — in severe iron overload, the signal becomes lower than that of adjacent muscles.
- Pathognomonic sign — shrunken, nodular liver with an abnormally low signal combined with severe iron overload of the pancreas.
Parametric R2* maps (R2 maps*) are also used for evaluation.
What other iron metabolism laboratory parameters besides ferritin need to be investigated for the diagnosis of haemochromatosis?
To assess iron metabolism in the diagnosis/verification of haemochromatosis, in addition to ferritin, sources indicate the following parameters:
- Transferrin saturation — used to exclude primary/hereditary haemochromatosis; saturation > 45% is indicated as diagnostically significant for hereditary haemochromatosis.
- Serum transferrin level — included in the comprehensive assessment of iron metabolism, including in the verification of secondary haemochromatosis.
- Total iron-binding capacity (TIBC) — included in the comprehensive study of iron metabolism.
- Serum iron level — also included in the comprehensive assessment of iron metabolism parameters.
The classic picture of primary haemochromatosis is easy to remember as «bronze diabetes»: bronze (pigmented) skin, pancreatic damage (diabetes), and liver damage (cirrhosis). And on X-rays, we look for «hooks» (hook-like osteophytes) on the 2nd and 3rd fingers.
Class and exam questions
Which radiological sign of the hand is considered specific to haemochromatosis?
Formation of hook-like osteophytes on the radial surface of the metacarpal heads, predominantly of the 2nd and 3rd fingers.
What is the main difference between arthropathy in hemochromatosis and standard osteoarthritis?
Specific distribution: in haemochromatosis, the metacarpophalangeal joints are affected while the interphalangeal joints remain relatively intact (preserved), and wrist chondrocalcinosis is often concomitant.
Who is at risk for developing primary hemochromatosis?
Classically, the disease manifests in men aged 40 to 60 years.
What laboratory parameters correlate with the disease?
To confirm the diagnosis, detecting an elevated serum ferritin level is key.
What else to study on this topic
- Gout imaging and dual-energy CT (DECT)
- MRI diagnostics of seronegative spondyloarthritides
- Multicentric reticulohistiocytosis: erosive arthritis and differential diagnosis
- Hypertrophic pulmonary osteoarthropathy and lamellar periostosis
- Wrist chondrocalcinosis: causes and radiodiagnostics
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