Extra-articular manifestations of rheumatic disease - dermatological symptoms
Lesion and what it points to
- *In rheumatology the skin is the accessible biopsy site and the earliest diagnostic clue*
- Organised by the lesion, because that is how she will meet it:
| Lesion | Points to |
|---|---|
| Palpable purpura | Small-vessel vasculitis - IgA vasculitis, cryoglobulinaemia, ANCA-associated, drug |
| Erythema nodosum | Sarcoid, IBD, streptococcus, TB, drugs, pregnancy, Behcet |
| Livedo reticularis / racemosa | Antiphospholipid syndrome, PAN, cholesterol emboli, vasculitis |
| Digital ulcers, pitting scars | Systemic sclerosis, vasculitis, APS |
| Malar rash / discoid lesions | SLE |
| Heliotrope, Gottron papules | Dermatomyositis |
| Psoriasiform plaques + nail change | Psoriatic arthritis, reactive arthritis |
| Pyoderma gangrenosum | IBD, RA, myeloproliferative disease |
| Oral/genital ulceration | Behcet, SLE, reactive arthritis, IBD |
| Sclerodactyly, calcinosis, telangiectasia | Systemic sclerosis / CREST |
| Rheumatoid nodules | Seropositive RA |
| Erythema migrans | Lyme disease (travel history - not endemic in Australia) |
Epidemiology
- Erythema nodosum: F>M ~4-6:1, peak 20-40; ~30-50% idiopathic
- Cutaneous involvement occurs in >70% of SLE and is the presenting feature in ~25%
- Psoriasis precedes arthritis in ~70% of psoriatic arthritis (arthritis first in ~15%)
- Raynaud phenomenon: ~3-5% of the population; *>95% of systemic sclerosis*
- Pyoderma gangrenosum: ~50% have an associated systemic disease
Erythema nodosum - a septal panniculitis
- Delayed-type hypersensitivity to a circulating antigen -> septal inflammation of subcutaneous fat WITHOUT vasculitis
- *Causes* (mnemonic-worthy, and frequently examined)
- DRUGS - oral contraceptive pill, SULFONAMIDES, salicylates, NSAIDs, penicillins, bromides/iodides
- INFECTION - STREPTOCOCCUS (the commonest identifiable cause), TUBERCULOSIS, MYCOPLASMA, Yersinia, Salmonella, Campylobacter, fungal (histoplasmosis, coccidioidomycosis)
- INFLAMMATORY BOWEL DISEASE - tracks with disease activity, unlike pyoderma gangrenosum
- SARCOIDOSIS - Lofgren syndrome: erythema nodosum + bilateral hilar lymphadenopathy + fever + ankle arthritis (good prognosis, self-limiting, no biopsy needed)
- PREGNANCY
- Behcet disease, malignancy (lymphoma), idiopathic (~30-50%)
Vasculitis - vessel size determines the lesion
| Vessel | Lesion |
|---|---|
| Small (capillary/venule) | PALPABLE PURPURA, urticarial vasculitis, splinter haemorrhages |
| Medium (muscular artery) | Livedo racemosa, nodules, DIGITAL INFARCTS, punched-out ULCERS, mononeuritis multiplex |
| Large | Limb claudication, absent pulses, bruits (no primary skin lesion) |
Other mechanisms
Others
- Photosensitive lupus rashes - UV-induced keratinocyte apoptosis -> anti-Ro/SSA binding -> subacute cutaneous lupus (annular/psoriasiform, photodistributed)
- Pyoderma gangrenosum - neutrophilic dermatosis; PATHERGY (lesions provoked by trauma - including SURGICAL DEBRIDEMENT, which makes it worse)
- Systemic sclerosis - endothelial injury -> fibroblast activation -> excess collagen
The high-yield rheumatological rashes
- *Malar (butterfly) rash - SPARES the nasolabial folds (rosacea and dermatomyositis do not*)
- *Discoid lupus - scarring, follicular plugging, scarring alopecia*, dyspigmentation
- *Subacute cutaneous lupus - annular or psoriasiform, photodistributed, anti-Ro positive, drug-induced by hydrochlorothiazide, terbinafine, PPIs, TNF inhibitors*
- *Dermatomyositis - heliotrope, GOTTRON PAPULES over the knuckles (psoriasis and SLE spare the knuckles and affect the interphalangeal skin - the discriminator), shawl/V sign, mechanic's hands*, nailfold capillary changes
- *Psoriasis - extensor surfaces, scalp, umbilicus, NATAL CLEFT, nails (pitting, onycholysis, oil drop sign); examine these hidden sites in any undiagnosed arthritis*
- *Gout - tophi* on the helix, olecranon, Achilles, finger pads
- *Systemic sclerosis - sclerodactyly, digital pitting scars and ulcers, calcinosis, telangiectasia*, salt-and-pepper pigmentation, microstomia
- *Behcet - recurrent painful oral AND genital ulceration, pathergy*, erythema nodosum-like lesions, acneiform pustules
- *Adult-onset Still disease - evanescent salmon-pink macular rash with fever spikes*
- *Rheumatoid - nodules (extensor surfaces, seropositive), vasculitic nail-fold infarcts, pyoderma gangrenosum, rheumatoid neutrophilic dermatosis*
Investigations
- *BIOPSY the right lesion at the right time*
- Vasculitis: a fresh (<48 h) purpuric lesion, and send a SECOND sample for DIRECT IMMUNOFLUORESCENCE (IgA -> IgA vasculitis; pauci-immune -> ANCA-associated)
- Erythema nodosum: a DEEP INCISIONAL or punch biopsy including subcutaneous fat - a shave biopsy misses the septal panniculitis entirely; in practice a typical case does not need biopsy
- Erythema nodosum work-up: ASOT/anti-DNase B and throat swab, CXR (hilar nodes, TB), CRP/ESR, FBE, faecal calprotectin, pregnancy test, drug history, Mantoux/QuantiFERON
- Vasculitis work-up: urinalysis with microscopy (the cheapest and most important test), UEC, ANCA, ANA/ENA, complement C3/C4, cryoglobulins, hepatitis B and C, HIV, EPG, blood cultures, CXR
- Nailfold capillaroscopy - distinguishes primary from secondary Raynaud; giant capillaries and dropout predict systemic sclerosis
Erythema nodosum - management
Erythema nodosum
- *Treat the cause and reassure - self-limiting over 3-6 weeks; lesions resolve like a bruise WITHOUT ulceration or scarring*
- Bed rest, leg elevation, compression stockings
- NSAIDs (avoid in IBD-associated disease); potassium iodide for persistent lesions
- Colchicine in Behcet-associated disease; systemic corticosteroid only after infection is excluded
- *Stop the culprit drug, including the oral contraceptive*
Cutaneous vasculitis - management
Cutaneous vasculitis
- *Urinalysis and creatinine in every patient* - the skin lesion is visible, the glomerulonephritis is not
- Skin-limited disease: remove the trigger, rest, elevation, NSAID, colchicine, dapsone
- Systemic involvement (renal, neurological, gut, pulmonary): corticosteroid + immunosuppression
- ANCA-associated: rituximab or cyclophosphamide + glucocorticoid, with AVACOPAN (oral C5a receptor antagonist) as a steroid-sparing addition
- Cryoglobulinaemic: treat the hepatitis C with direct-acting antivirals; rituximab and plasma exchange for severe disease
Lupus skin disease
- *Rigorous photoprotection - SPF 50+, hats, clothing (and check vitamin D*)
- Hydroxychloroquine (<=5 mg/kg/day) - first line for all cutaneous lupus
- Topical corticosteroid or calcineurin inhibitor; methotrexate, mycophenolate; anifrolumab or belimumab for refractory disease
- SMOKING CESSATION - smoking markedly reduces hydroxychloroquine efficacy in cutaneous lupus
Pyoderma gangrenosum
- *DO NOT DEBRIDE - pathergy makes it worse (the classic and consequential error*)
- High-dose corticosteroid or ciclosporin; infliximab (especially with IBD)
- Wound care, analgesia, treat the underlying disease
Digital ulcers in systemic sclerosis
- Warmth, smoking cessation, nifedipine; sildenafil; IV iloprost for critical ischaemia; bosentan to prevent NEW ulcers
Psoriatic skin and joint disease
- Methotrexate; biologics by domain - TNF, IL-17 (secukinumab, ixekizumab), IL-23 (guselkumab, risankizumab), IL-12/23 (ustekinumab); JAK inhibitors
- IL-17 inhibitors can precipitate or worsen IBD - avoid where enteropathic disease coexists
Lesion associations
- Erythema nodosum - *sarcoidosis (Lofgren), IBD, streptococcal infection, TB, mycoplasma, Yersinia, drugs (OCP, sulfonamides, salicylates, NSAIDs), pregnancy, Behcet, lymphoma*
- Palpable purpura - IgA vasculitis, cryoglobulinaemia (hepatitis C), ANCA-associated vasculitis, drug hypersensitivity, infection
- Livedo - antiphospholipid syndrome (Sneddon syndrome), PAN, cholesterol embolism, calciphylaxis
- Pyoderma gangrenosum - IBD, RA, seronegative arthritis, myeloproliferative disease, monoclonal gammopathy (IgA)
- Raynaud phenomenon - systemic sclerosis, SLE, MCTD, Sjogren, dermatomyositis, cryoglobulinaemia, drugs (beta blockers, ergot), vibration injury, thoracic outlet
- Psoriasis - psoriatic arthritis, metabolic syndrome, IBD, uveitis
- Behcet - HLA-B51, Silk Road ancestry, uveitis, venous thrombosis
- Sweet syndrome - malignancy (AML), IBD, infection, G-CSF, azathioprine
- Calcinosis - dermatomyositis (especially juvenile), CREST
- Drug reactions - TNF inhibitors (psoriasiform eruption, lupus), hydralazine/PTU (ANCA vasculitis), allopurinol (DRESS/SJS - **HLA-B58:01***)
Course
- Erythema nodosum - *resolves over 3-6 weeks WITHOUT ulceration or scarring, fading like a bruise; recurrence in ~20-30%, mostly idiopathic or IBD-associated*
- Cutaneous vasculitis - skin-limited disease usually resolves within weeks; the risk is unrecognised systemic disease - repeat urinalysis
- Discoid lupus - *scars permanently, causes irreversible scarring alopecia and dyspigmentation; ~5-10% progress to systemic lupus*
- Pyoderma gangrenosum - heals with characteristic cribriform (sieve-like) atrophic scars; recurrence common
- Systemic sclerosis digital ulcers - recurrent, slow-healing; risk of infection, osteomyelitis and amputation
- *The skin lesion often predicts the systemic course: anti-TIF1-gamma DM rash -> malignancy; lupus pernio -> chronic sarcoidosis; nailfold capillary dropout -> systemic sclerosis; pathergy -> Behcet**
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