Rheum Flashcards
burning and pins and needles in the hand, wakes at night. Diagnosis?
carpal tunnel
OA management
- exercise to build muscle strength
- weight loss
- analgesia [PO+topical]
- intra-articular steroid injections
- PT/OT, heat/cold packs, walking aids
- surgery
which is more specific for rheumatoid arthritis, anti CCP or rheumatoid factor?
anti CCP
monitoring for DMARDs
3 monthly FBC & LFT
methotrexate for ank spond?
doesn’t work on spine so only for other affected joints
what is crest syndrome?
type of scleroderma - calcinosis, raynauds, oesophageal, sclerodactyly, telangectasia
osteoporosis Mx
bloods to rule out [vit D, Ca, TFT]
alendronic acid > risedronate > zolendronate
Adcal
how long would you continue a patient on a bisphos for osteoporosis?
5 yrs then break
what chest xray changes might you see in chronic sarcoidosis?
hilar lymph node enlargement
sarcoid Mx
steroids
does it matter is RA patient is rheumatoid factor +ve or -ve when considering a biologic?
yes - unlikely to start in a -ve patient as they dont respond well
what can you do if methotrex Pt having nausea
split dose [twice a week instead of once] and ^folic acid from weekly to daily (except on methotrex day)
why do methotrex patients take folic acid?
reduces SEs
DMARD side effects
nausea, reduced appetite, sore mouth, diarrhoea
ank spond patients suffer with what bowel prob?
crohns
why might you switch pt from methotrex PO to SC?
100% of injection absorbed
GI SEs
Risk factors for RA
Female
Smoking
Genetic
Management of hyper mob/ Ehler Danlos type 3
Pain relief
Physio
Complications/ serious manifestations of ehler danlos/ hypermob
Dislocated eye lenses
Cardiac - aneurysm, valvular
If patient presents with RA picture + also has psoriasis, how do you diagnose?
Rh +ve = RA
Rh -ve = psoriatic
calcium deposits in joint causing inflamm. Dx?
pseudogout
what type of drug is hydroxychloroquine?
DMARD
what is Takayasu’s arteritis and Tx?
large vessel vasculitis. steroids,methotrex
what hip problem is an associated complication of steroid use? and Ix
avascular necrosis
MRI (xray wont necessarily show)
what is the clinical triad of wegener’s granulomatosis? (3 areas affected)
upper resp tract
lower resp tract
kidneys
describe some Sx of wegeners gran
oral ulcers bloody nasal discharge nasal bridge collapse (saddle) sinusitis haematuria dyspnoea
Mx of fibromyalgia
meds - pain relief + anti dep
pain clinic
exercise
CBT/ councelling
what effect does fluoxetine have on sleep
^ wakefulness
what WBC change might steroids induce on FBC
^neutrophils
what is the name of the deformity seen in RA patients where there is flexed PIP and extended DIP?
boutonniere
what is the name of the deformity seen in RA patients where there is flexed DIP and extended PIP?
swan neck
what blood results might indicate active RA/ inflamm?
anaemia
^platelets
^ESR/CRP
72 yr old
3 day Hx pain/swelling of 1 knee
O/E apyrexial, knee warm/swollen w/ effusion
Mx?
could be trauma/ RA/ OA, but aspirate and culture synovial fluid to rule out septic arthritis
46 yr old male, DM/ HTN/ hyperlipidaemia
2 day Hx cute onset pain/ swelling of 1 ankle, cant weightbear.
Differetial diagnoses?
gout
septic arth
risk factors for septic arth
elderly malignancy imm supp prosthesis injection trauma chronic arthr
most common organism for septic arth
staph aureus
if septic arth suspected should you start Abx immediately or wait til after aspirate
wait - Abx could skew culture result / false neg
Ix for septic arth
blood culture
inflamm markers
joint aspirate + culture
usual Abx for septic arth
+other mx
fluclox
surgical washout
multiple hot swollen joints, spreading to other joints, moving. + skin lesions. Diagnosis?
gonoccocal arth
extraarticular features of RA
lung nodules
scleritis/episcleritis
vasculitis
^risk of IHD
Differential for temporal arteritis in scalp tenderness
Migraine
ESR and age criteria for temp arteritis diagnosis
Both >50
how does gout present
1 JOINT
acute
inflamed
big toe metatarsophalangeal in >50%
common joints for gout other than big toe metatarsophalangeal (in >50%)
ankle foot small joints of hand wrist elbow knee
gout is caused by deposition of what
monosodium urate crystals
what factors could precipitate gout
trauma surgery starvation infection diuretics
other than gout, what may occur due to long term raised plasma urate?
tophi [deposits] in pinna, tendons, joints
renal disease [stones, interstitial nephritis]
differentials for gout
septic arth reactive arth haemarthrosis CPPD (pseudogout) palindromic RA
give 5 risk factors for gout
male age post-menopause women impaired renal Fn HTN metabolic syndrome diuretics, antihypertensives, aspirin, warfarin, diet [alcohol, red meat etc] genetic myelo/lymphoproliferative disorders psoriasis tumour-lysis syndrome
what will light microscopy of synovial fluid show in gout
-vely birefringent urate crystals [needle-shaped]
Ix in gout
joint aspirate and light microscopy of synovial fluid
serum urate levels
XR
what might XR of gout show
soft tissue swelling only in early stages
punched out erosions in juxta-articular bone
Mx of acute gout
high dose NSAID colchisine if NSAID contra-I beware renal impairment for both! steroid [PO/IA/IM] rest + elevate, bed cage, ice pack
gout prevention
weight loss avoid fasting avoid alcohol/meat excess avoid aspirin prophylaxis: allopurinol
when would you start someone on gout prophylaxis
> 1 attack/yr
tophi
renal stones
precautions when starting allopurinol
it may trigger an attack, so wait 3 weeks after an episode, and cover with regular NSAID/colchicine for 6 weeks/6 months respectively
how does acute calcium pyrophosphate deposition present
large joint
monoarthropathy
acute
in the elderly
how does chronic calcium pyrophosphate deposition present
inflammatory RA-like symmetrical polyarthritis + synovitis
what will light microscopy of synovial fluid show in calcium pyrophosphate deposition ?
and on XR?
weakly positively birefringent crystals [rhomboid shaped]
soft-tissue calcium deposition
Mx of calcium pyrophosphate deposition
cool packs, rest aspiration intra-articular steroids NSAIDs +/- colchisine chronic: methotrex, hydroxychloroquine
Sx of OA
pain crepitus ['crunching/creaking'] background ache at rest worse with prolonged activity brief stiffness after rest [10-15 mins] instability ['gives way'] reduced ROM (mild inflamm) boney swelling [heberbens dip/bouchards pip] KNEE, HIP, DIP/PIP/CMC
xr features OA
LOSS Loss of joint space Osteophytes Subarticular sclerosis Subchondral cysts
risk factors for septic arthritis
pre-existing joint disease [RA] DM imm.supp. chronic renal failure recent joint surg prosthetic joint IV drug abuse age >80
Ix in septic arth
urgent joint aspiration M+C
blood cultures
XR may be normal
CRP may be normal
main differential for septic arth
crystal arthropathies
common organisms for septic arthritis
staph aureus
strep
neisseria gonococcus
gram -ve bacilli
Mx of sertic arthritis
Abx
arthrocentesis/surgical washout/debridement
risks of NSAIDs
GI bleed
^stroke/MI risk
renal injury
the spondyloarthropathies are a group of related chronic inflamm conditions. They include:
ank spond
enteric arthropathy
psoriatic arth
reactive arth
what are the shared clinical features of the spondyloarthropathies [these include Ix findings]
- seronegative [RF-ve]
- HLA B27
- axial arthritis [spine+sacroiliac]
- asymmetrical large joint oligo/mono
- enthesitis [plantar fasc/Achilles tendonitis/costochon]
- dactylitis
- extra-articular [eyes/rash/oral ulcers/valve/IBD]
main joints effected in ank spond
spine
sacroiliac joints
typical presentation of ank spond.
+ other complications/ mainfestations
young man gradual onset low back pain worse at night morning stiffness sacroiliac joint pain > buttocks/hips reduced spinal movement in all directions enthesitis
acute iritis
osteoporosis
aortic valve incompetence
pulm apical fibrosis
XR/ MRI findings in ank spond
SI joint space narrowing/widening
ankylosis/fusion
sclerosis
erosions
MRI: as above + active inflamm [bone marrow oedema]
what are syndesmophytes? they are pathognomic for what disease?
bony proliferations due to enthesitis between ligaments and vertebrae.
ank spond
Mx of ank spond
exercise/ PT NSAIDs TNFa blockers [adalimumab/ etanercept] local steroid inj bisphos [osteoP risk]
hip replacement / (spinal osteotomy)
associations of enteric arthropathy
IBD
GI bypass
coeliac
Mx of psoriatic arthritis
IA steroid [in monoarthritis]
methotrex/leflunomide/sulfasalazine [in poly/oligo/ persistent monoarthritis]
NSAIDs
apremilast
etanercept/adalimumab/infliximab
ustekinumab
clinical features of reactive arthritis
arthritis
Sx of STI
iritis
keratoderma blenorrhagica [brown papules on soles and palms]
circinate balanitis [Chlam penile ulceration]
mouth ulcers
enthesitis
what is the triad of reiter syndrome
urethritis
arthritis
conjunctivitis
what are the features of systemic sclerosis
scleroderma (skin fibrosis)
internal organ fibrosis
microvascular abnormalities
what antibody is present in 90% of systemic sclerosis patients?
ANA
in systemic sclerosis, skin disease is limited or diffuse. Which areas are affected in limited?
face, hands, feet
[NB. both limited and diffuse can have organ fibrosis but it happens later in limited]
what condition of the lungs, that can be life threatening, is ass. w/ limited systemic sclerosis?
How is it treated?
pulm HTN
sildenafil
sjogrens syndrome can be primary or secondary to what?
SLE
RA
systemic sclerosis
give 4 features of sjogrens
reduced tears [dry eyes, keratoconjunctivitis sicca]
reduced salivation [Xerostomia, caries]
parotid swelling
vaginal dryness, dyspareunia
dry cough
dysphagia
polyarthritis, arthralgia, raynauds, lymphadenopathy, vasculitis, lung, liver, kidney, peripheral neuropathy, myositis, fatigue
what CA are sjogrens patients at ^ risk of
non-hodgkins lymphoma
Mx of sjogrens
artificial tears frequent drinks gum/pastilles NSAIDs, hydroxychloroquine for arthralgia severe: imm supp
give 5 conditions in which raynauds is seen
SLE systemic sclerosis RA dermato/polymyositis atheroma polycythaemia rubra vera hypothyroid
what causes raynauds
paroxysmal vasospasm
Mx of raynauds [drug + advice]
rule out an underlying disease
keep warm
smoking cessation
nifedipine
features of polymyositis
progressive symmetrical proximal muscle weakness \+ muscle inflamm myalgia arthralgia dysphagia dysphonia resp weakness
fever, arthralgia, raynauds, initerstitial lung fibrosis, myocarditis, arrhythmia
dermatomyositis features
those of myositis [muscle inflamm + weakness]
plus skin signs:
macular rash (shawl),
lilac purple rash with oedema on eyelids,
nail fold erythema,
gottrans papules (red over knuckles, elbows, knees)
fever, arthralgia, raynauds, initerstitial lung fibrosis, myocarditis, arrhythmia
what enzymes might you see increased in the plasma in myositis [muscle inflamm/ breakdown]
CK
LDH
ALT/AST
50 yr old female presents with gradually worsening thigh weakness, difficult to stand from sitting without using arms. Her muscles and joints ache, she also has a red rash over her chest, upper back and shoulders. On examination you notice some red papules over her knuckles and elbows. Bloods show ^CK. EMG shows fibrillation potentials.
Diagnosis? And how would you confirm the diagnosis?
dermatomyositis
muscle biopsy
Mx of myositis
pred
imm supp.
cytotoxics
hydroxycloroquine/topical tacrolismus for skin disease
diseases associated with rheumatoid factor
sjogrens RA felty's syndrome SLE systemic sclerosis
diseases associated with ANA
SLE
systemic scleroiss
autoimmune hepatitis
sjogrens
anti ds DNA = what disesase
SLE
gastric parietal cell / intrinsic factor antibodies =
pernicious anaemia
alpha gliadin antibody, antitissue transglutaminase Ab …. what disease?
coeliac
thyroid peroxidase antibodies seen in what diseases?
hashimoto’s thyroiditis
grave’s
islet cell antibodies, glutamic acid decarboxylase ab see in….
DM type 1
glomerular basement membrane antibody = what disease
goodpastures
cANCA seen in what diseases
granulomatosis with polyangiitis [wegeners]
microscopic polyangiitis
polyarteritis nodosa
pANCA seen in…
microscopic polyangitis
churg-strauss
goodpastures
acetylcholine receptor antibody seen in ….
myasthenia gravis
pathology of SLE
multisystem autoimmune
autoantibodies > immune complexes > imflammation + damage
give 8 features of lupus [can be Sx, manifestations, Investigation findings]
malar/butterfly rash discoid rash alopecia oral/nasal ulcers synovitis serositis [pleurisy, pleural effusion, pleural rub/ pericardial pain, pericardial effusion, pericardial rub, pericarditis on ECG] lupus nephritis [proteinuria, RC casts] seizure, psychosis, mononeuritis multiplex, myelitis, neuropathy haemolytic anaemia leucopenia thrombocytopenia \+ve ANA/ anti-dsDNA/low complement/^ESR
mX of SLE
hydroxychloroquine topical steroids for skin flares NSAIDs azathiop, methotrex, mycophenalate belimumab renal: control BP, ACEi/ARB, RRT, transplant
suncream
features of anti-phospholipid syndrome
+ Mx
antibodies cause CLOT: Coag defects [clots: arterial/venous, cerebral, renal] Livedo reticularis Obs [miscarriages] Thrombocytopenia
Mx = anticoagulants
give the types of large vessel and medium vessels vasculitides
large: GCA, takayasu
med: polyarteritis nodosa, kawasaki
what is the pathology in takayasu’s?
What Sx does this produce?
who does it affect?
vasculitis of aorta and its major branches
granulomatous
stenosis, thrombosis, aneurysms
aortic arch: dizzy, weak arm pulses, visual change
systemic: fever, weight loss, malaise
renal artery stenosis: high BP
women age 20-40, in japan
complications of takayasu’s arteritis
renal artery stenosis aortic valve regurg aortic aneurysm, dissection ischaemic stroke IHD
Mx of takayasu’s
pred
(methotrex, cyclophos)
BP Control
angioplasty/stenting/bypass in stenosis
list the small vessel vasculitides
ANCA-ass:
microscopic polyangiits
granulomatosis with polyangiits [Weg]
churg-strauss [eosinophilic GWP]
immune complex:
goodpastures
cryoglobulinaemic vasculitis
IgA vasculitis[HSP]
Mx of large/medium/small vessel vasculitis
large: steroids (+steroid sparing later)
med/small: steroid + e.g. cyclophos/methotrex/azathiop
Hx sounds like temporal arteritis but patient is under 55, what other vasculaitis would, you consdier?
takayasu’s
histroy sounds like temporal arteritis but biopsy is normal. what’s going on?
skip lesions, dont be put off by -ve biopsy
what would you give a patient with temporal arteritis on long term steroids to avoid risks of steroid treatment?
bisphos
calcium with colecalciferol
PPI
what does polyarteritis nodosa do
necrotizing vasculitis
aneurysms and thrombosis
> infarct
medium vessels
features of microscopic polyangiitis
glom. neph.
pulm haemorrhage
systemic features of vasculitis
fever malaise weight loss arthralgia myalgia
GI features of vasculitis
pain
infarct
perf
malabsorption
renal features of vasculitis
hypertension haematuria proteinura casts renal failure glom.neph infarcts
neuro + psych features of vasculitis
stroke fits chorea psychosis confusion impaired cognition altered mood mononeuritis multiplex, polyneuropathy
what condition does polymyalgia rheumatica often occur alongside?
GCA
features of polymyalgia rheumatica
<2 weeks onset
aching, tender, morning stiffness
in shoulders, hips, proximal muscles
NOT WEAKNESS
fatigue, fever, weight loss, anorexia, depression
age>50
[carpal tunnel, tenosynovitis, polyarthritis]
what investigation could help you distinguish polymyalgia rheumatica from myositis/myopathy?
CK
raised in myositis/myopathy
not in PMR
polymyalgia rheumatica Mx
pred
(+ bisphos)
+/-methotrex
fibromyalgia Mx
GET
CBT
amitriptilline/ pregab
duloxetine if alongside depression/anx
what causes sudden blindness in GCA
optic nerve ischaemia
features of hypertensive retinopathy on fundoscopy
“silver wiring” - shiny hardened arteries
“AV nipping”
cotton wool spots [retinal infarcts where narrowed arterioles have become blocked]
hard exudates
macular oedema
papilloedema
flame haemorrhages
^BP damages retinal vessels
“roth spots” (small retinal infarcts) occur in what condition?
infective endocarditis
difference in fundoscopy with central vein occlusion ad branch vein occlusion
central = stormy sunset branch = confined to wedge of retina
what eye changes might be seen in leukaemia
retinal haemorrhages
differentials of red eye: acute glauc, ant uveitis, conjunc, subconjunc.haem.
What does the pupil look like in each
acute glauc - fixed dilated (oval)
ant. uveitis - small, stuck to lens
conjunct/subconjunc haem = normal
differentials of red eye: acute glauc, ant uveitis, conjunc, subconjunc.haem.
which has a steamy/ hazy cornea?
acute glauc
differentials of red eye: acute glauc, ant uveitis, conjunc, subconjunc.haem.
Tx for each
acute glauc: IV acetazolamide + pilocarpine
ant uveitis: pred drops + cyclopentolate
conjunc: nothing or chloramphenicol
subconjunc. haem. : resolves spont
causes of erythema nodosum
sarcoidosis
drugs [sulfasalazine for UC, COCP]
strep infection
less common:
IBD, TB, viruses/fungi
describe what erythema multiforme looks like + location
‘target lesions’
symmetrical +/- central blister
on palms/soles, limbs
erythema migrans [papule developing into a spreading large erythematous ring with central fading] is pathognomic of what disease?
lyme disease
pyoderma gangrenosum associations
[10cm purulent necrotic ulcers on legs/abdo/face]
sex predominance?
Tx?
IBD autoimmune hepatitis granulomatosis with polyangiitis [Weg] myeloma neoplasia
female predominance
PO steroids +/-ciclosporin
skin manifestations of crohns
perianal/vulval/oral ulcers
erythema nodosum
pyoderma gangrenosum
skin manifestations of dermatomyositis
gottron’s papules
shawls sign
heliotrope rash on eyelids
skin manifestations of DM
ulcers
necrobiosis lipoidica
granuloma annulare
acanthosis nigricans
skin manifestations of coeliac
dermatitis herpetiformis
skin manifestations of hyperthyroid
pretibial myxoedema
thyroid acropachy
skin manifestations of liver disease
palmar erythema spider naevi gynaecomastia decreased pubic hair jaundice bruising scratch marks
Tx for itch of dermatitis herpetiformis
dapsone
which rheumatological diseases include raynauds
systemic sclerosis
SLE
polymyositis
dermatomyositis
differentials for monoarthritis
SA
OA
crystal [gout, CPPD]
trauma [haemoarthrosis]
differentials for oligoarthritis [<5]
crystal psoriatic reactive ank spond OA
differentials for symmetrical polyarthritis[ >5]
RA
OA
viruses [hepABC, mumps]
systemic conditions [SLE, malig, haemochrom etc]
differentials for asymmetrical polyarthritis [>5]
reactive
psoriatic
systemic [SLE, malig, haemochrom etc]
what do you send synovial fluid for following joint aspiration [ie what are you investigating for
WCC
gram stain
polarised light microscopy [crystals]
culture
red flags for sinister causes of back pain [malig/infection/inflamm]
<20 or >55 acute in elderly thoracic morning stiffness constant/worsening bilat/alternating leg pain neuro disturbace incl sciatica nocturnal pain sphincter distrbance worse supine fever, night sweats, weight loss recent or current infection malignancy Hx imm supp [steroids/HIV] abdo mass leg claudication or exercise related leg weakness/numbness [spinal stenosis]
a) which nerve roots is straight leg raise?
b) what = a positive test?
c) pathology usually suggested
a) L4, L5, S1
b) raise straight leg = pain below knee, worse on dorsiflex
c) irritation to sciatic nerve, most common is lumbar disc prolapse
sciatic nerve is formed from which spinal roots?
L4-S3
a) which nerve are you assessing in femoral stretch test?
b) what = +ve test
a) L2-L4
b) patient prone, knee flexed. hip ext > pain in front of thigh on
list 4 most likely causes of back pain in 15-30 yr olds
prolapsed disc trauma fracture ank-spond spondylolisthesis pregnancy
give 3 most likely causes of back pain in 30-50 yr olds
prolapsed disc
malig
degenerative
give 4 most likely causes of back pain in >50s
osteoporosis wedge fracture malig degen pagets myeloma spinal stenosis
Ix in red flag back pain
MRI, XR FBC urine/serum electrophoresis ESR/CRP PSA U+E LFT [alp]
Mx of back pain
neuro deficit- urgent neurosurg r/v
non-spec - advise exercise, analgesia, physio, acupuncture
[surg]
features of cauda equine compression
alternating / bilat root pain in legs
saddle parastheisa
los o anal tone
bladder/bowel incont
features of acute cord compression
bilateral pain
LMN signs @ level of compression
UMN + sensory loss below
sphincter disturbance
causes of acute cord compression + cauda equina
bony mets large disc protrusion myeloma cord/paraspinal tumour TB abscess
where is the pain felt + which movements would demonstrate weakness in L2 nerve root lesion
pain across upper thigh
hip flexion and adduction
L3 nerve root lesion
a) where’s the pain? [dermatome]
b) weakness in what movements?
c) reflex affected?
a) across lower thigh
b) hip adduction, knee ext
c) knee jerk
L4 nerve root lesion
a) where’s the pain? [dermatome]
b) weakness in what movements?
c) reflex affected?
a) across knee to medial malleolus
b) knee ext, foot inversion, dorsiflex
c) knee jerk
L5 nerve root lesion
a) where’s the pain? [dermatome]
b) weakness in what movements?
c) reflex affected?
a) lateral shin to dorsum of foot and big toe
b) hip ext + abduction, knee flex, foot + big toes dorsiflex
c) big toe jerk
S1 nerve root lesion
a) where’s the pain? [dermatome]
b) weakness in what movements?
c) reflex affected?
a) post calf to lateral foot + little toe
b) knee flexion, foot and toe plantar flex, foot eversion
c) ankle jerk
factors that ^risk or worsen RA
female
smoking
50-60s
HLA DR4/1
features of RA
symm swollen painful stiff small joints of the hands and feet
worse in morn
larger joints can be involved/ fluctuating/various presentations
extraart and systemic Sx in RA
fatigue fever weight loss pericarditis pleurisy
early exam signs in RA
inflamm swollen MCP, PIP, MTP symm tenosynovitis [inflamed tendon] bursitis
late exam signs in RA
ulnar deviation - wrists and fingers
boutonieres, swan neck, Z thumb
what rare complication of RA can threaten the cervical spinal cord
atlanto-axial joint subluxation
lung extra art manifestations of RA
nodules
pleural
interstitial fibroiss
bornchiolitis obliterans
extra art manifestations of RA - cardiac
cardiac nodules
IHD
pericardiits
percardial effusion
Ix findings in RA
RF +ve
antiCCP
FBC anaemia of chronic disease, ^platelets
^ESR/CRP
XR - soft tissue swelling, osteopenia, red. joint space, erosions, sublux, carpal destruciton
US/MRI - synovitis, erosions
RA Mx
DMARDs [metho, sulfa, hydrox] biologics [inflix/ritux] steroids [IM/IA/PO] nsaids PT/OT surg CV risks stop smoking
SEs of methotrex/ risks
infections pneumonitis oral ulcers nausea + V hepatotox teratogenic
what diseases should pt be screened for befroe starting dmards
TB
hepB/C
HIV
SEs of biologics
infection
reactivation of TB
worsening HF
blood disorders
pathophysiology behind pagets disease of bone + resulting problems
^bone turnover [^osteoblasts + osteoclasts]
remodelling, bone enlargement, deformity, weakness
clinical features of pagets disease of bone
deep boring pain
bony deformmity + enlargement
pelvis, lumbar spine, skull, femur, tibia[sabre]
cpmplicaptions of pagets disease of bone
pathological fracures OA ca2+^ nerve compression from bone overgrowth: deafness, root CCF osetosarcoma
XR findings in pagets disease of bone
bone enlargement
patchy cortical thickening with sclerosis, osteolysis, deformity
axial/long bone/skull
bloods in pagets disease of bone
^Ca2+
normal PO43-
^^^alp
mx of pagets disease of bone
analgesia
bisphos
