pathology: rheumatic diseases – overview

Rheumatic diseases can be categorised as follows:

Rheumatoid arthritis (RA)

  • seropositiv
  • seronegativ
  • viral arthritis

Spondylarthritis SpA

DD Spondylarthritis:

Childhood/juvenile idiopathic arthritides

Kristallarthritis

Arthritis (including PMR) and vasculitis

collagenoses

Non-inflammatory diseases

Enteropathy-associated arthritis

In ulcerative colitis, arthritis occurs in 15% of cases, usually shortly after the more severe episode, and 15% also develop sacroileitis. In 5% of cases, ankylosing spondylitis similar to ankylosing spondylitis affects the spine. In Crohn’s disease, the rate for arthritis (mostly affecting the colon) and sacroileitis is slightly higher at 20%. The ankylosing spondylitis-like symptoms are slightly higher at 6%. The accompanying arthritides of both diseases are monarthritides or oligoarthritides, often affecting knee joints or ankle joints. The symptoms usually subside after a few days or weeks; it is rare for them to last for months. The chronification rate is only 10%, but damage to the joints remains in 25% of cases. The rate of concomitant Bechterew’s symptoms is 3-4%. 10% of CED patients have concomitant asymptomatic sacroileitis . In addition to some other facultative extraintestinal symptoms, CED tends to cause enthesiopathies (insertional tendopathies) or granulomas in bones or muscles. The arthritides are usually treated with NSAIDs and only rarely with glucocorticoids. Sulfasalazine not only improves the intestinal situation, but also the symptoms of the joints.

In principle, enteropathic arthritis also occurs less frequently outside of CED, for example in infectious enteritis, usually caused by Salmonella, Shigella or Yersinia. Coeliac disease (gluten-sensitive enteropathy) and Whipple’s disease can also cause enteropathic arthritis.

External Links:
https://www.aerzteblatt.de/archiv/436/Rheumatism -und-Magen-Darm-Trakt
https://www.sanderbusch.de/_uploads/files/downloads/mayet/s11377-010-0501-1_mayet_sanderbusch_de.pdf

Juvenile idiopathic arthritis JIA

Juvenile idiopathic arthritides are arthritides that occur before the age of 16 and last for at least 6 weeks. They often primarily affect the synovium and occur in episodes. Painful movement restrictions and swelling and rest pain of the affected joint or joints (50% are oligoarthritides, followed by seronegative polyarthritides, further seropositive polyarthritides, psoriasis-arthritis, enthesitis-associated JIA, systemic JIA (Still’s disease)) are the main symptoms.
At 16 / 100,000 / a, the incidence is rather low, girls are more frequently affected. Pain is often absent in young children, but movement behaviour is altered.

Externe Links:
https://www.rheumaliga.ch/rheuma-von-a-z/juvenile-idiopathische-arthritis
https://www.msdmanuals.com/de/profi/p%C3%A4diatrie/juvenile-idiopathische-arthritis/juvenile-idiopathische-arthritis-jia

Autoinflammatory syndrome

Group of over two dozen diseases with an excessive non-specific immune reaction. It is characterised by periodic episodes of fever of unknown cause and systemic manifestations. Other symptoms such as myalgia, arthralgia/arthritis, abdominal pain and others may also occur: serositis (peritonitis/pleuritis/pericarditis), hepatosplenomegaly, exanthema, uveitis, conjunctivitis, secondary amyloidosis, neurological symptoms.
The cause is usually a monogenetic mutation. Depending on the perspective, CED, psoriasis, gout and arteriosclerosis are included. The transition to autoimmunological diseases is fluid.

External links:
https://flexikon.doccheck.com/de/Autoinflammatorisches_Syndrom
https://www.usz.ch/krankheit/autoinflammatorische-syndrome/

Rheumatic fever

Rheumatic fever RF is an aseptic disease that can occur post-infectiously after an infection with group A streptococci. It occurs only very rarely with timely antibiotic treatment, but in 3% of cases not treated with antibiotics, and in the case of reinfection with group A streptococci, the probability of recurrence of rheumatic fever is 50%. Mostly children and adolescents are affected between the ages of 3 and 16, adults only very rarely. In industrialised countries, the incidence has been declining for a long time thanks to better hygiene and the availability and use of antibiotics in cases of the relevant pathogen group. Populations at low risk have less than 2 new cases per 100,000 children between the ages of 5 and 14, which corresponds to a prevalence of less than one per thousand. In developing countries (95% of cases worldwide), however, RF is still the most common heart disease in children, causing 150,000 deaths worldwide each year. Accordingly, risk factors associated with living conditions can be identified: Living in rural or urban slums, poverty, crowded living conditions, poor access to medical care and inadequate coordination in health care. Girls are also more frequently affected and some genetic factors are suspected.
The disease is caused by the production of antibodies against part of the streptococcal membrane, which ultimately leads to the immune system damaging the endothelial cells of the heart valves. Like syphilis, RF is a disease with many possible manifestations (chameleon). Adults tend to show joint manifestations of large joints such as the ankle joint and knee joint, which appear after 10 days and later often jump within hours (polyarthritis). Peripheral spread to smaller joints is not uncommon.
Children show fewer joint manifestations, rather cardiac ones, which are common anyway with 60% of all cases. Pancreatitis often develops, which can affect the pericardium, myocardium and endocardium to varying degrees. If the pericardium is affected, veruculous endocarditis develops due to antigen-antibody complexes. At 70%, the mitral valve is very frequently affected, 25% of which is also the aortic valve, which is rarely affected in isolation. Pulnomal and tricuspid valves are far less frequently affected and usually secondary. If the myocardium is affected, this is usually asymptomatic; precordial pain is to be expected in the pericardium.
Endocarditis can be asymptomatic for years and lead to heart failure. If the brain is affected, this manifests itself as chorea minor, which usually affects young women and may only appear months later: the hands and facial muscles are hyperkinetic, the muscles are generally hypotonic and hyporeflexia develops. The affection is unilateral or bilateral. The skin may be affected with a pale red, marginal erythema (erythema marginatum anulare rheumaticum), more commonly on the trunk, less frequently on the extremities and very rarely on the face. Subtutaneous rheumatoid nodules up to 2 cm in size can occur on the bony prominences of the hands, feet and elbows. They usually occur when carditis is also present. The latency interval of the various symptoms varies. Fever, headache and sweating are general symptoms. The diagnosis is made primarily on the basis of anamnesis and clinical findings using the Jones criteria.

External links:
https://www.msdmanuals.com/de/profi/p%C3%A4diatrie/verschiedene-bakterielle-infektionen-bei-s%C3%A4uglingen-und-kindern/rheumatisches-fieber
https://register.awmf.org/assets/guidelines/023-027l_S2k_Akutes-rheumatisches-Fieber-Poststreptokokken-reaktive-Arthritis_2024-04. pdf
https://flexikon.doccheck.com/de/Rheumatisches_Fieber?utm_source=www.doccheck.com&utm_medium=DC%2520Search&utm_campaign=DC%2520Search%2520contenttype%253Aall&utm_content=DC%2520Search%2520rheumatic%2520fever
https://de.wikipedia.org/wiki/Rheumatisches_Fieber

Giant cell arteritis (RZA, temporal arteritis)

Giant cell arteritis is a rheumatological autoimmune disease in which inflammation occurs in the walls of large vessels for unknown reasons. The disease occurs in 40-60% of cases together with polymyalgia rheumatica (PMR). Rather general symptoms such as low fever, weight loss, night sweats, myalgia, sometimes severe cephalgia can accompany the disease, but also more specific symptoms such as circulatory disorders, visual complaints (diplopia, scotoma, ptosis, blurred vision), complaints in the pelvic girdle or, as in PMR, in the shoulder girdle. If the inflammation is pronounced, the vessel walls can become unstable and rupture, which can also affect the aorta in the form of aortic dissection and aneurysm. Imaging procedures can visualise the changes in the vessels. The temporal artery must always be examined as well. If it is also affected, it is also painful. If it is affected, there is a risk of blindness (optic nerve ischaemia), but timely intervention usually at least prevents blindness on both sides. Carotid arteries are often affected, but not intracranial but extracranial ones. Occasionally, stroke or TIA occur, as well as disorders of the jaw.

The localisation varies from monofocal to multicocal to disseminated. The onset of the disease can be sudden or gradual. The disease is not uncommon; asymptomatic courses or undiagnosed cases also occur.

External links:
https://www.msdmanuals.com/de/profi/erkrankungen-des-rheumatischen-formenkreises-und-des-bewegungsapparats/vaskulitis/riesenzellarteriitis#Therapie_v904638_de
https://flexikon.doccheck.com/de/Riesenzellarteriitis?utm_source=www.doccheck.com&utm_medium=DC%2520Search&utm_campaign=DC%2520Search%2520content_type%253Aall&utm_content=DC%2520Search%2520giant cell arteritis

Takayasu’s arteritis (TA)

External link:
https://www.msdmanuals.com/de/profi/erkrankungen-des-rheumatischen-formenkreises-und-des-bewegungsapparats/vaskulitis/takayasu-arteriitis
https://flexikon.doccheck.com/de/Takayasu-Arteriitis

Polyarteritis nodosa (PAN, polyarteritis nodosa)

Very rare systemic necrotising vasculitis of medium-sized vessels with nodule formation in the vessel walls and swelling of the vessel walls with consecutive restriction of the lumen. Blood clots can then lead to ischaemia or tissue infarction. Aneurysms can also develop. General symptoms include high fever and fatigue, weight loss and night sweats. The other symptoms depend on the vessels affected, including the eponymous skin nodules.

Initially, aggressive treatment with corticosteroids and immunosuppressants is used, switching to milder immunosuppressants as soon as possible. At the beginning of the 1990s, this disease was often fatal, but today the prognosis is much better. Recurrences are rarer than with other vasculitis.

External links:
https://flexikon.doccheck.com/de/Polyarteriitis_nodosa
https://www.msdmanuals.com/de/profi/erkrankungen-des-rheumatischen-formenkreises-und-des-bewegungsapparats/vaskulitis/polyarteriitis-nodosa-pan

ANCA-associated vasculitis

Necrotising vascular disease, especially of the small arteries and arterioles, venules and capillaries, which usually affects parts of the respiratory tract, but can also affect the kidneys (glomerulonephritis), eyes, skin or nerves. The course of the disease can be life-threatening.

External links:
https://flexikon.doccheck.com/de/ANCA-assoziierte_Vaskulitis
https://register.awmf.org/assets/guidelines/060-012l_S3_Diagnostik-Therapie-ANCA-assoziierten_Vaskulitiden_2024-08_2.pdf

IgA vasculitis (Purpura Schoenlein Hennoch)

Vasculitis affecting mostly children (adults 10 times rarer) of the small vessels, especially the skin and mucous membranes of the GIT and kidneys, in which immune complexes are deposited in the vessel walls. Purpura is the most common vasculitis in children. Among the triggering infections, those caused by beta-hemolytic streptococci that occurred a few weeks ago are common, but it also occurs as a reaction to medication.
The extremities often show pronounced petechiae, which do not discolour with gentle pressure. The lower extremities are usually affected with a distal to proximal course. Further symptoms may follow. Damage to the vessels leads to bloody diarrhoea, haematemesis and melena in the GIT, haematuria in the kidneys and oedema in the joints. The joint pain occurs without clinically recognisable inflammation and does not damage the joints. In the case of bloody diarrhoea with the presence of petechiae, puprura is quite likely to be the cause. A previous infection or medication is important in the medical history.
In addition to a slight fever, non-specific pain occurs. The typical course lasts a few weeks with several episodes; chronic progressive courses are rare. The kidneys must be monitored regularly, they can fail and the blood pressure can escalate with the development of corresponding headaches.
The diagnosis is made as a diagnosis of exclusion after the relevant DD has been ruled out.

External links:
https://www.rheuma-liga.de/rheuma/krankheitsbilder/iga-vaskulitis
https://flexikon.doccheck.com/de/Purpura_Schoenlein-Henoch
https://register.awmf.org/assets/guidelines/185-002l_S2k_Immunglobulin_A_Vaskulitis_Purpura_Sch%C3%B6nlein-Henoch_2022-08.pdf

Behcet’s syndrome (BS, Behçet’s syndrome)

Behcet’s syndrome is a recurrent inflammatory disease of small and large vessels (arteries and veins) that can cause both venous and arterial thrombosis. The onset is usually after the age of 20, rarely in childhood. There are strong ethnic/regional differences, so the disease is common between the Mediterranean and China, but hardly occurs in the USA. It is probably autoimmunological and is based on previous viral or bacterial infections. The genetic predisposition appears to be HLA-B51.
The main symptom and usually the first symptom are recurrent painful oral ulcers in the mouth similar to stomatitis aphtosa, sometimes also on the penis, scrotum, vulva and vagina. Other skin symptoms may also occur, such as erythema nodosum or superficial thrombophlebitis. In 25-75% of cases, the eyes are also affected with various disorders, whereby there is a risk of blindness in the case of neuritis or vascular occlusion. Mild, self-limiting arthralgias that do not damage the joint are possible, usually of the knee joints or other large joints. Aneurysms, pseudoaneurysms, haemorrhages and stenoses as well as thromboses (arterial and venous) can develop in the vessels. Infestation of large vessels is possible, but often remains clinically inapparent. If the CNS is affected, MS-like symptoms, pyramidal tract signs and aseptic meningitis or meningoencephalitis may result. If the GIT is affected, abdominal pain and ulcers similar to Crohn’s disease may result. Depending on the neurological, vascular and gastrointestinal manifestations, fatal courses are also possible. In principle, the risk is highest in younger men, and further in the case of clear vascular manifestations or a high number of relapses.
General symptoms include fever and a feeling of illness/discomfort. DD includes diseases from various areas, including reactive arthritis, SLE, herpes infections and CED.

https://www.msdmanuals.com/de/profi/erkrankungen-des-rheumatischen-formenkreises-und-des-bewegungsapparats/vaskulitis/beh%C3%A7et-krankheit
https://behcet-zentrum.de/fuer-aerzte/
https://www.medizin.uni-tuebingen.de/de/das-klinikum/einrichtungen/kliniken/medizinische-klinik/innere-medizin-ii/rheumatologie/morbus-behcet
https://www.medizin.uni-tuebingen.de/de/das-klinikum/einrichtungen/kliniken/medizinische-klinik/innere-medizin-ii/rheumatologie/morbus-behcet


Cryoglobulinaemic vasculitis


Cryoglobulins are immunoglobulins or immunoglobulin complexes, most commonly IgG-IgM complexes, which can reversibly form gel-like clumps when the blood becomes too cold. These can lead to vasculitis in the small and smallest vessels. This form of vasculitis occurs primarily, but also secondarily in the context of various diseases (pathogen-related, haematological or autoimmunological, such as Sjörgen’s syndrome, SLE, RA or sarcoidosis), as more immunoglobulins are formed in these cases. Neuropathies, GN, arthralgias and purpura, especially of the acra, are possible in the clinical picture.

GBM vasculitis (Goodpasture syndrome)

GBM vasculitis is a very rare (1-2 / 1 million / a) autoimmunological small vessel vasculitis with skin manifestations in the lungs and kidneys. Antibodies act against the glomerular and pulmonary capillary basement membrane (alveolar haemorrhage) and cause a type 2 allergic reaction (cytotoxic). The manifestation in the lungs and kidneys is known as Goodpasture’s syndrome, but in 50% of cases only the kidneys are affected, which is known as anti-GBM nephritis. The renal symptoms of the rapidly progressing nephritis, which can lead to terminal renal failure if left untreated, range from fatigue, hypertension and oedema to the complete symptoms of renal failure, which can develop within weeks if left untreated. If the lungs are affected, cough and dyspnoea are present, later haemoptysis and possibly pulmonary siderosis. The symptoms of pulmonary haemorrhage can occur weeks or even years before the renal symptoms. Other general symptoms include fever and weight loss. Rapid recognition and treatment of the syndrome are important in order to preserve organs and life.

External links:
https://www.msdmanuals.com/de/profi/lungenkrankheiten/diffuse-alveol%C3%A4re-h%C3%A4morrhagie-und-pulmorenales-syndrom/goodpasture-syndrom
https://flexikon.doccheck.com/de/Anti-GBM-Erkrankung

Systemic lupus erythematosus (SLE)

SLE is a chronic inflammatory autoimmunological multi-organ disease, often occurring post-infectiously, which preferentially affects young women. 70-90% of those affected are female. The incidence differs according to ethnicity, blacks and Asians are more frequently affected, in some countries SLE is similarly common to RA. A genetic predisposition is assumed. Reversible lupus-like symptoms are also induced by some medications. The spectrum of symptoms is broad and the following is described:

  • Joints (in 90%): the spectrum ranges from intermittent arthralgia to acute polyarthritis. Joint involvement is usually non-destructive, except in cases of protracted disease. Damage then affects the MCP, PIP, DIP.
  • Skin/mucous membrane: the characteristic flat or raised butterfly-shaped facial erythema occurs here, leaving out the area between the nasolabial folds. In contrast to rosacea, skin atrophies, pustules and papules are absent. Further erythema in other regions is possible, as is mucosal involvement (buccal mucosa, gums, transition from hard palate to soft palate. Alopecia also occurs. Panniculitis can occur in the subcutaneous fat layer. The vasculitic skin lesions cause various skin symptoms, e.g. palmar erythema or erythema of the fingers, further urticaria, purpura, petechiae, nodules on toes, fingers, nose, ears. The vasoconstriction leads to Raynaud’s syndrome.
  • Cardiopulmonary recurrent pleuritis (sicca or exudative) occurs, mild impairment of lung function, but rarely aseptic pneumonitis. Alveolar haemorrhage, pulmonary hypertension, pulmonary embolism or shrinking lung syndrome (dyspnoea, elevated diaphragm, inspiratory chest pain, restrictively reduced lung volume without fibrosis) are also possible. In the area of the heart, pericarditis often occurs, with myocarditis being secondary. Infestation of the heart valves, coronary vasculitis or Libman-Sacks endocarditis are serious complications. Accelerated development of arteriosclerosis can become severe.
  • Lymphatic tissue: generalised lymphadenopathy often occurs here, rarely mediastinal lymphadenopathy, in 10% splenomegaly.
  • Neurologically, CNS, PNS and the meninges can be affected, which can lead to a variety of symptoms: Headache, bloodless apoplexy, subarachnoid haemorrhage, aseptic meningitis, peripheral and cranial neuropathies, transverse myelitis, dysfunction of the cerebellum, but also reduction in cognitive and mnestic performance, personality changes or psychosis.
  • renal lupus nephritis can occur at any time, ranging from benign asymptomatic to catastrophic, e.g. in membranoproliferative glomerulonephritis. Hypertension and oedema can develop, leucocytes, erythrocyte cylinders and proteinuria can be seen in the urine.
  • haematologically, anaemia, leucopenia and thrombocytopenia occur, with additional antiphospholipid antibody syndrome also arterial or venous thrombosis and often pregnancy complications.
  • Gastro-intensive symptoms occur due to vasculitis and impaired intestinal motility. Nausea, vomiting, abdominal pain, peritonitis, symptoms of pseudo-obstruction or perforation are possible. Only rarely is the liver parenchyma affected.
  • Gynaecologically, an episode during pregnancy can lead to miscarriages. Pregnancies should be planned and well monitored for remission.


External links:
https://www.usz.ch/krankheit/systemischer-lupus-erythematodes/
https://www.msdmanuals.com/de/profi/erkrankungen-des-rheumatischen-formenkreises-und-des-bewegungsapparats/rheumatische-autoimmunerkrankungen/systemischer-lupus-erythematodes?query=lupus

Sjögren’s Syndrome

Sjögren’s syndrome is a rather common (prevalence 4/1000) autoimmunological chronic inflammatory systemic collagenosis of unknown cause, which is mainly characterised by dryness of various mucous membranes (including the mouth and eyes) („sicca syndrome“). The cause is a secretory disorder of the corresponding exocrine glands due to lymphocytic infiltration, but other organs can also be affected. Sjögren’s syndrome mainly affects middle-aged women. HLA-DR3 predisposed in whites. Some other diseases such as RA, SLE, Hashimoto’s thyroiditis, primary biliary cirrhosis are associated with secondary Sjögren’s syndrome (prevalence approx. 400,000 in Germany). If the eyes are affected by dryness, they feel sandy and gritty, but do not itch. Chewing and swallowing are impaired due to the lack of saliva. Candida infections also occur more frequently, stones are more likely to form in the ducts and teeth decay more quickly. In addition to the mouth, other membranes and mucous membranes can also be affected, such as the nose, throat, larynx, bronchi, vagina and vulva. The dryness of the airways can lead to an irritating cough. In 1/3 of cases, the parotid gland is enlarged and only slightly painful (DD patoris tumour).
In 50% arthralgias occur, but the joints are not damaged, in 33% an arthritis similar to that of RA, but unlike there, it is not erosive. Other possible symptoms include Raynaud’s syndrome, lymphadenopathy, often less severe interstitial involvement of the lungs, vasculitis, pancreatic insufficiency or pancreatitis and chronic hepatobiliary disease. Vasculitis may damage peripheral or central nerves. Puprura or GN is also possible. Pseudolymphomas, B-cell lymphomas and Waldenström’s macroglobulinaemia can also occur. There is also a 40-fold higher risk of non-Hodgkin’s lymphoma. Accompanying general symptoms can include fatigue and alopecia.

External links:
https://www.msdmanuals.com/de/profi/erkrankungen-des-rheumatischen-formenkreises-und-des-bewegungsapparats/rheumatische-autoimmunerkrankungen/sj%C3%B6gren-syndrom?query=Sj%C3%B6rgen-Syndrom#Diagnose_v903779_de
https://www.rheuma-liga.de/rheuma/krankheitsbilder/sjoegren-syndrom
https://flexikon.doccheck.com/de/Sj%C3%B6gren-Syndrom

Systemic sclerosis / scleroderma (SSc)

Systemic sclerosis is a chronic disease with fobrosis and vascular abnormalities in skin, joints and internal organs (preferably cardiopulmonary, renal, GIT). Vascular damage, fibroblast activation, overproduction of collagen are the most important pathomechanisms.
The most common symptoms are polyarthralgia, Raynaud’s syndrome, dysphagia, heartburn, swollen fingers with thickened skin (scleroderma) and possibly contractures. Similar symptoms can also be chemically induced.
The disease can become lethal, especially when affecting the heart, lungs and kidneys. If severe hypertension occurs in principle, this is usually due to a scleroderma renal crisis, although hypertension may be absent if the kidneys are affected. A distinction is made between

  • limited systemic sclerosis
  • Generalised systemic sclerosis including skin involvement
  • Systemic sclerosis without scleroderma

The slowly progressive limited form is characterised above all by Raynaud’s syndrome, telangiectasia, oesophageal motility disorders and sclerodactyly. Reflux (GERD) is possible, as is pulmonary hypertension. In contrast, the progression of generalised systemic sclerosis is rather rapid, interstitial lung involvement and renal complications are the most serious symptoms, followed by GIT complications, and Raynaud’s syndrome is less severe. The systemic form without scleroderma has mainly visceral manifestations, but does not affect the skin.

External links:
https://www.msdmanuals.com/de/profi/erkrankungen-des-rheumatischen-formenkreises-und-des-bewegungsapparats/rheumatische-autoimmunerkrankungen/systemische-sklerose?query=Systemische%20Sklerose%20(SSc)#%C3%84tiology_v904039_en
https://flexikon.doccheck.com/de/Systemische_Sklerose
https://www.rheuma-liga.de/rheuma/krankheitsbilder/sklerodermie

Polymyositis/Dermatomyositis/Autoimmunmyositis (PM/DM)

Polymyositis is a rare, presumably autoimmunological disease of the skeletal muscles and the heavily supplied internal organs kidneys, lungs and heart. If the skin is also affected, it is referred to as dermatomyositis. Around 15-20% of dermatomyositis cases occur together with a paraneoplastic syndrome, especially if the GIT is affected, the breast, the female genitalia, the lungs or a T-cell lymphoma is present. If the tumour is removed, dermatomyositis often heals. The disease usually manifests itself either in childhood or between the ages of 30 and 50.
Characteristic symptoms are mainly found in the skin: variously localised erythema (upper limbs, posterior neck, shoulders, upper back, sternum and ventral neck, lateral thigh), hyperkeratotic mechanic’s hands prone to fissures, hyperkeratosis and telangiectasis developing on the nail facsimile, as well as deck-chair sign (erythroderma with recessed skin folds) and calcinosis of the skin.
In the area of the internal organs, GN may occur, arrythmias, cardiomyopathies and conduction disorders, as well as weakness and pain, especially in the proximal limb muscles, and interstitial pneumonia.

External links:
https://www.msdmanuals.com/de/profi/erkrankungen-des-rheumatischen-formenkreises-und-des-bewegungsapparats/rheumatische-autoimmunerkrankungen/autoimmun-myositis
https://flexikon.doccheck.com/de/Dermatomyositis
https://www.altmeyers.org/de/dermatologie/dermatomyositis-ubersicht-981

Septic arthritis / infectious arthritis

Septic arthritis is a joint infection caused by bacteria or other microorganisms. The pathogens can enter the joint haematogenously (via the bloodstream), traumatically or per continuitatem (from neighbouring tissues). Preferred pathogens are known for all routes of infection, including streptococci, staphylococci and TB pathogens in the case of haematogenous infection. People with reduced immunity (deficiency), immunosuppression, joints previously damaged by joint diseases or endoprostheses are predisposed, whereby these not only predispose to post-infectious arthitis, but also to haematogenous infection. The knee joint is most frequently affected, followed by the hip joint and smaller joints such as the hand joint, finger joints, toe joints, shoulder joint or the OSG. Pain on movement and pain on movement are the most important symptoms alongside signs of inflammation and fever. If prostheses are affected, the clinical symptoms are usually more moderate and fever may be absent, but the prosthesis often becomes loose. Clear evidence is provided by a joint puncture, if this is unclear, also by biopsy of the synovia.

External links:
https://flexikon.doccheck.com/de/Septische_Arthritis
https://www.msdmanuals.com/de/heim/knochen-gelenk-und-muskelerkrankungen/infektionen-von-knochen-und-gelenken/infekti%C3%B6se-arthritis