Haemochromatosis (HC) is a group of phenotypically heterogeneous clinical syndromes, which may have a common molecular basis. Classical genetic haemochromatosis (GHC) is one of these syndromes and is a disorder of iron storage due to an increase in intestinal iron absorption, which results in progressive and massive iron deposition leading to fibrosis and organ malfunction. The liver, pancreas, heart and pituitary are commonly involved. There is a specific arthropathy and an association with osteoporosis. Clinically, the arthropathy may resemble rheumatoid arthritis, with acute attacks of inflammation associated with bilateral destruction of the metacarpophalangeal joints. However, bony joint swelling may occur, suggestive of osteoarthritis. Hip arthritis may be unduly severe and disabling. Haemochromatosis arthritis is composed of three radiographic categories: isolated chondrocalcinosis, hypertrophic osteoarthritis which is indistinguishable from pyrophosphate associated arthropathy, and disease specific changes such as subchondral radiolucency of the femoral head, hook-like osteophytes on the metacarpal heads and a degenerative predilection for the metacarpophalangeal joint rather than the scapholunate. The characteristic histological changes are: abnormal amounts of iron deposits, little or no signs of synovial inflammation and CPPD deposition. Subchondral radiolucency of the femoral head and atypical stripping of the cartilage from the subchondral bone are thought to be specific radiographic and histological changes of HC. The pathogenesis of HC arthritis has been associated with the presence of iron in joint tissue, a defect in cartilage metabolism and immunological dysfunction. Treatment has little effect on clinical, radiological or histological progression.

Multicentric reticulohistiocytosis is a rare multisystem disorder that reflects a reactive inflammatory response to an undetermined stimulus. While the disease is characterized as a dermatoarthritis, multiple organ systems including cardiac and skeletal muscle, the pleura and gastrointestinal tract have been involved in reported cases. The synovitis can be quite destructive with arthritis mutilans developing in a substantial percentage. The dermatitis may be particularly disfiguring when the face is involved. This chapter describes the clinical and laboratory features of the 33 cases of MRH previously reviewed by Barrow and Holubar and an additional 33 cases that have appeared in the medical literature since that report. We note an apparent decline in frequency of some manifestations of MRH. This may be due in part to the nature of the recent reports which often present a brief clinical report and focus primarily on specific disease associations, unusual manifestations, new organ system involvement or treatment regimens. The primary cell involved in the reactive inflammatory response of MRH is the phagocytic tissue histiocyte (macrophage). While uncontrolled proliferation of these reticulohistiocytes is seen in several infectious and malignant conditions there is presently no direct evidence of a particular organism or neoplasm involved in the aetiopathogenesis of MRH. There is evidence of tuberculosis exposure in one third of cases with active tuberculosis present in 5%. Likewise, malignancies are reported concomitantly with MRH in 15-28% of cases. The therapeutic trend in MRH is to treat early and aggressively to prevent the devastating arthropathy and disfiguring cutaneous sequelae. This recommendation, however, is largely based on anecdotal reports and thus the physician encountering a case of MRH needs to proceed with circumspection.

Adult onset Still's disease seems to be the adult form of Still's disease in children. The key symptoms of the disease are high spiking fever, arthritis and a macular or maculopapular, salmon-pink evanescent rash, almost always accompanied by neutrophilic leukocytosis and frequently by sore throat, intense myalgias, lymphadenopathy, splenomegaly and signs of serositis. Tests for IgM rheumatoid factor and antinuclear antibody are characteristically negative. With respect to haematologic abnormalities, the disease may give rise to several problems. First, there is a neutrophilic leukocytosis, which currently is unexplained, and often a normocytic normochromic anaemia, that may be profound. The anaemia has the characteristics of anaemia of chronic inflammatory disease. Both abnormalities disappear after effective treatment of the disease or at spontaneous remission. Secondly, there might be a problem to differentiate AOSD from malignant haematological disorders, including malignant lymphoma and leukaemia, especially when the picture is dominated by lymphadenopathy, splenomegaly, fever and leukocytosis. Although in rare cases the differential diagnosis is extremely difficult, diagnosis can mostly be made or excluded by peripheral blood smear staining, bone marrow biopsies and occasionally lymph node biopsy. Finally, like the juvenile counterpart, AOSD is occasionally complicated by sometimes life-threatening diffuse intravascular coagulation. Factors that might be important in the development of this complication include severe disease activity, liver abnormalities and particular drugs including salicylates, other NSAIDs and some slow-acting antirheumatic drugs. Prompt therapy, including withdrawal of the drug, corticosteroids and sometimes anticoagulant therapy have been successfully applied to most patients.

Henoch-Schönlein purpura probably results from a reaction in a host sensitized by an infective stimulus. This stimulus leads to the synthesis of IgA antibody, the presence of circulating immune complexes and a leukoclastic vasculitis involving IgA resulting in renal and dermatological manifestations. The risk factors, the causal organism and the reason for the association with IgA nephropathy remain unknown.

Bone and joint involvement in the leukaemias is discussed. Particular emphasis is placed upon osteoarticular presentations which may predate the haematological changes or divert attention from the primary pathology. A description of acute and chronic graft versus host disease is presented with particular emphasis on the rheumatological manifestations.

The management of the haemophilias has been improved by the advent of potent consistent clotting factor replacement therapy. The previously lethal major complications such as intracerebral haemorrhage are now rare, and the infective complications of treatment, most notably hepatitis and AIDS, are now potentially preventable with the new synthetic products. There is also the prospect of 'cure' by gene insertion therapy. Advanced arthropathy has been minimized but not prevented by early effective treatment of haemarthroses, and there is a diminishing legacy of severely affected patients many of whom may require joint replacement surgery. The present group of such patients has a high prevalence of HIV-1 infection and an increased risk of joint sepsis. The available avenues of treatment for the subacute stage of the arthropathy have not been particularly effective, emphasizing the need to prevent recurrent bleeding. The development of a multidisciplinary team-management approach in centres of expertise has been a significant factor in the improved longevity, life satisfaction and preserved mobility now available to most haemophiliacs.