Pocket Medicine: The Massachusetts General Hospital Handbook of Internal Medicine (106 page)

Descriptions of skin manifestations

•
Psoriasis
: erythematous plaques with sharply defined margins often w/ thick silvery scale •
Circinate balanitis
: shallow, painless ulcers of glans penis and urethral meatus •
Keratoderma blennorrhagica
: hyperkeratotic lesions on soles of feet, scrotum, palms, trunk, scalp •
Erythema nodosum
: red tender nodules due to panniculitis, typically on shins; Ddx incl. idiopathic, infxn, sarcoid, drugs, vasculitis, IBD, lymphoma •
Pyoderma gangrenosum
: neutrophilic dermatosis → painful ulcers w/ violaceous border; Ddx incl. idiopathic, IBD, RA, myelogenous leukemia
Psoriatic arthritis subtypes
(
Lancet
2011;377:2127)
•
Monoarticular/oligoarticular
(eg, large joint, DIP joint, dactylitic digit): most common initial manifestation •
Polyarthritis
(small joints of the hands/feet, wrists, ankles, knees, elbows): indistinguishable from RA, but often asymmetric •
Arthritis mutilans
: severe destructive arthritis with bone resorption, esp. hands •
Axial disease
: similar to ankylosing spondylitis ± peripheral arthritis •
DIP-Limited
: good correlation with nail pitting and onycholysis
Clinical assessment
(
Nat Rev Rheumatol
2012;8:253)
•
Axial disease assessment

Severity of lumbar flexion deformity assessed by modified Schober’s test (
if <5 cm ↑ in distance between a point 5 cm below the lumbosacral jxn and another point 10 cm above, when going from standing to maximum forward flexion)

T-spine mobility (extension) and kyphosis severity measured by occiput-to-wall distance

•
Seronegative
: notable for absence of rheumatoid factor or autoantibodies; ± ↑ ESR

•
HLA-B27
: nonspecific, as common in general population (6–8%); most useful when high clinical suspicion but nl imaging;
90% of Pts w/ AS, but only 20–80% in other SpA •
Radiology

MRI preferred for early detection of inflammation (sacroiliitis)

Plain films detect late structural changes (SI erosions/sclerosis)

calcification of spinal ligaments w/ bridging symm syndesmophytes (“bamboo spine”)

squaring and generalized demineralization of vertebral bodies (“shiny corners”)

•
Infectious evaluation for reactive arthritis
(
studies do not r/o)

U/A, PCR of urine and/or genital swab for Chlamydia; urethritis usually due to Chlamydia infxn preceding arthritis, but also can see sterile urethritis post dysentery

stool Cx, C. diff toxin

consider HIV in workup of reactive or psoriatic arthritis

Treatment approach
(
Lancet
2011;377:2127;
Rheumatology
2012;51:1378)
• Untreated disease may lead to irreversible structural damage and associated ↓ function • Early physiotherapy beneficial •
NSAIDs
: 1st line; rapidly ↓ stiffness and pain; prolonged, continuous administration may modify disease course but associated w/ GI and CV toxicity •
Intra-articular corticosteroids
in mono-or oligoarthritis; limited role for systemic steroids, esp. for axial disease •
Conventional DMARDs
(eg, MTX and SAS): no efficacy for axial disease or enthesitis; may have role in peripheral arthritis, uveitis and other extra-articular manifestations •
Anti-TNFs
: effective for both axial and peripheral manifestations; improves function (Ann Rheum Dis 2006;65:423) and may slow progression of structural changes (Curr Rheumatol Rep 2012;14:422); unclear role of other biologics •
Other

Abx in reactive arthritis if evidence of active infxn; consider prolonged abx for refractory Chlamydia ReA (Arthritis Rheum 2010;62:1298)

Involve ophthalmologist for any evidence of inflammatory eye disease (may benefit from steroid eye drops or intravitreal steroid injections)

Treat underlying IBD when appropriate

INFECTIOUS ARTHRITIS & BURSITIS

ETIOLOGIES & DIAGNOSIS OF INFECTIOUS ARTHRITIS

Etiologies

•
Bacterial
(nongonococcal): early diagnosis required •
Gonococcal
(N. gonorrhea): consider in sexually active young adults • Viral: parvovirus, HCV, HBV, acute HIV; typically polyarticular, may mimic RA • Mycobacterial: monoarticular or axial (Pott’s disease)

• Fungal: Candida (esp. prosthetic joints), coccidiomycosis (valley fever), histoplasmosis • Other: Lyme, mycoplasma

Diagnosis
(
JAMA 2007;297:1478)

• H&P w/ poor sensitivity and specificity for septic arthritis; ∴
arthrocentesis
should be performed as soon as suspected • Take care not to tap through an infected area thus introducing infxn into joint space • ✓ Synovial fluid cell count, Gram stain, bacterial culture, crystals

WBC >50k w/ poly predom
suspicious for bact. infxn; crystals do not r/o septic arthritis!

BACTERIAL (NONGONOCOCCAL) ARTHRITIS

Epidemiology & risk factors

•
Immunocompromised host
: diabetics, HIV, elderly, SLE,
etc.

•
Damaged joints
: RA, OA, gout, trauma, prior surgery/prosthetic, prior arthrocentesis (rare) •
Bacterial seeding
: bacteremia secondary to IVDU, endocarditis or skin infection

direct inoculation or spread from contiguous focus (eg, cellulitis, septic bursitis, osteo)

Clinical manifestations
(
JAMA
2007;297:1478;
Lancet
2010;375:846)
• Acute onset
monoarticular arthritis
(>80%) w/ pain (Se 85%), swelling (Se 78%), warmth • Location:
knee
(most common), hip, wrist, shoulder, ankle. In IVDU, tends to involve other areas (eg, sacroiliac joint, symphysis pubis, sternoclavicular and manubrial joints).

•
Constit. sx
: fevers (Se 57%), rigors (Se 19%), sweats (Se 27%), malaise, myalgias, pain • Infection can track from initial site to form fistulae, abscesses or osteomyelitis • Septic bursitis must be differentiated from septic intra-articular effusion
Additional diagnostic studies
(
JAMA
2007;297:1478)
• Synovial fluid:
WBC usually >50k
(Se 62%, Sp 92%) but can be <10k,
>90% polys
; Gram stain
in
75% of Staph,
50% of GNR; Cx
in >90%.

Synovial bx for Cx most sens.

•
Leukocytosis
(Se 90%, Sp 36%) •
Blood cultures
in >50% of cases, ~80% when more than 1 joint involved • Conventional radiographs usually normal until after ~2 wk of infection when bony erosions, joint space narrowing, osteomyelitis, periostitis can be seen •
CT & MRI
useful esp. for suspected hip infection or epidural abscess
Treatment
(for native joints)
• Prompt empiric antibiotics guided by Gram stain after surgical drainage. If Gram stain
, empiric Rx w/ vancomycin; add anti-pseudomonal agent if elderly, immunosupp.