Hyponatremia due to secondary adrenal insufficiency

Thanks to Jess for presenting the fascinating case of a middle-aged woman with family history of autoimmune disease who presented with acute onset of fatigue and abdominal pain, found to have vitiligo on exam.  Work up revealed hyponatremia due to a secondary adrenal insufficiency, pancytopenia, and panhypopituitarism possibly due to a yet to be diagnosed autoimmune disorder!


Clinical pearls

  • Remember that hyponatremia is a problem of water regulation that can be compounded by low solute intake.
  • Primary adrenal insufficiency is disorder at the level of the adrenal glands and manifests with low sodium and high serum potassium levels.
  • Secondary adrenal insufficiency is disorder at the level of the pituitary and manifests with low/normal sodium and normal potassium levels (because low cortisol leads to high ADH levels and hyponatremia).
    • Make sure to do work up to rule out panhypopituitarism.  Keep in mind that the most sensitive test for HPA access integrity is LH/FSH.
  • Tertiary adrenal insufficiency is disorder at the level of the hypothalamus and presents similarly to secondary AI.
  • Test for adrenal insufficiency with a cort-stim test and/or AM cortisol and ACTH levels.

Hyponatremia

Remember these three steps to working up hyponatremia:

  1. Is there a sodium problem? check serum osm
  2. Are the kidneys responding appropriately? check urine osm
  3. Is ADH revved up for a hemodynamic reason? check urine Na 

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Adrenal insufficiency

Adrenal insufficiency
Source: NIDDK.gov

Primary AI:

  • Failure of adrenal glands
  • Causes: Addison’s (most common in the US), infiltrative processes (TB, sarcoid), hemorrhage, toxins
  • Labs would show ↓Na and ↑potassium (b/c aldosterone is gone)

Secondary AI:

  • Failure of pituitary (low ACTH)
  • Causes: pituitary lesions, surgeries, TBI, drugs
  • Clinically may present with loss of other anterior pituitary hormones
  • Labs would show ↓Na (because low cortisol leads to high ADH levels) but normal potassium levels (b/c aldosterone is active)

Tertiary AI:

  • Failure of hypothalamus (low CRH)
  • Causes: more commonly iatrogenic (cessation of high dose glucocorticoid therapy without taper) or post surgical interventions.

Hypopituitarism

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Hypophysitis:

  • Inflammation of the pituitary
  • Four categories based on histologic findings:
    • Lymphocytic
      • Most common form
      • Seen in late pregnancy and post-partum period
      • Also associated with CTLA4 inhibitors like ipilimumab
    • Granulomatous
      • Idiopathic or secondary to GPA, sarcoid, TB
    • Plasmacytic (IgG4-related)
    • Xanthomatous (most rare)
  • Clinical presentation
    • Headache out of proportion to exam findings
    • Preferential decrease in ACTH and TSH ⇒ adrenal insufficiency and hypothyroidism
  • Prognosis:
    • Pituitary size eventually normalizes but pituitary loss of function is often permanent.

 

Angioedema and hyperkalemia management

Thanks to Audris for presenting the case of a middle-aged man with vasculopathy on ACEi who presented with angioedema requiring intubation!  We discussed the  diagnostic work up and management of angioedema as well as hyperkalemia!


Clinical Pearls

  • First order of business when suspecting angioedema is the ABCs!
  • Treat angioedema in the acute setting with H1 blockers and steroids, even if you are suspicious of a non-histaminergic pathway.
  • Always assess for concurrent anaphylaxis (hypotension or bronchospasm in addition to hives or angioedema).  If anaphylaxis is present, then treatment involves IM 0.3-0.5 mg of 1:1000 dilution epinephrine (1mg/mL), repeat every 20 minutes until symptoms resolve (max 3 doses)
  • If you have access to a functioning kidney, favor loop diuretics over cation exchange binders (i.e. kayexalate) to lower serum potassium!
  • Patiramer is much better tolerated than kayexalate and has a more favorable side effect profile.
  • Calcium gluconate has a role in the treatment of hyperkalemia when EKG changes are present. Give a dose and repeat the EKG.  If no improvement, repeat to a maximum of 3 doses until EKG has normalized.

Angioedema 

  • 3 pathophysiologic subtypes:
    • Mast cell/histamine mediated
      • Etiologies:
        • Allergic reactions: food/insect stings, latex, drugs. Can also be idiopathic. IgE type 1 hypersensitivity
        • Direct mast cell release: drugs (opiates, contrast). IgE is not involved.
        • ASA/NSAIDs: via IgE or direct mast cell release
        • Chronic urticaria w/w/o angioedema
      • S/sx affecting organ systems other than the skin? Suspicious for anaphylaxis ⇒ give epi
      • Treatment: H1 blockers, glucocorticoids. 
    • Bradykinin mediated
      • Inhibition of enzymes involved in the degradation of bradykinin, or deficiency/dysfunction of complement C1 inh
      • More prolonged time course, develops over 24-46 hours and resolves within 2-4 days
      • Relationship between trigger and onset of symptom is not as apparent
      • Not associated with other s/sx. More common to have abdominal pain due to bowel wall involvement.
      • Treatment: bradykinin pathway mediators (ecallantide, icatibant), C1 inhibitor concentrate, or plasma replacement.
    • Unknown mechanism
      • Idiopathic angioedema
      • Infections (in children)
      • CCBs
      • Other drugs: sirolimus, everolimus, amiodarone, metoprolol, risperidone, paroxetine, and etanercept, inhaled cocaine.
      • Herbal meds
      • Urticarial vasculitis
      • Hypereosinophilic syndrome and Gleich syndrome

 

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Hyperkalemia

Agents that reduce serum potassium via transient intracellular shift:

  • Insulin: give with D50 if normoglycemic to avoid hypoglycemia and be sure to check FSG hourly for 4 hours after to ensure no hypoglycemia develops
  • Albuterol (10-20 mg) nebs: this is significantly higher than the dose we give in COPD (2.5 mg) and is equal to ~8 treatments! So make sure to continue the nebs when the patient arrives on the floor from the ER if they are still hyperkalemic.
  • NaHCO3: best for management of chronic hyperkalemia in the outpatient setting.  In the acute management of hyperkalemia, alkalinization of serum with a large bicarb load can lead to a reduction in serum calcium levels.  Lower serum calcium can lead to more cardiac membrane instability and fatal arrhythmias!

Agents that eliminate potassium from the body:

  • Loop diuretics: first choice if a functioning kidney is available!
  • Cation exchange binders: preferred when kidneys are not available
    • Patiramer (available at VMC), much more tolerable than kayexalate and highly effective at lowering serum potassium.  Like kayexalate, it works over hours to days.
    • Sodium zirconium: similar to patiramer but not currently available
    • Kayexalate: not pleasant to take orally. Also carries with it the slight risk of colonic ischemia especially in post renal transplant patients and those with baseline colonic dysfunction (due to infection or inflammation).
  • Dialysis

Indication for using calcium gluconate: when EKG changes are noted.  Repeat doses (maximum 3) until EKG changes have resolved.

Cavitary lung lesions and SJS/TEN

Today, we discussed the case of a Vietnamese man who presented with chronic cough, 40 pound weight loss, and joint pain, found to have cavitary lesions in his lungs with work up revealing pulmonary TB as well as tophaceous gout on urate-lowering therapy with allopurinol leading to SJS/TEN.


Clinical Pearls: 

  • Cavitary lung lesions have a broad differential (see below) aside from TB.
  • Risk factors for developing SJS/TEN include HIV (100x higher risk), genetics (especially Asians and South Asians), autoimmune diseases, malignancy, and high dose/rapid infusion of offending meds.  Consider genetic testing prior to starting meds associated with this allergy (allopurinol, sulfa drugs, PCNs, AEDs, etc.) in at risk populations.
  • Nikolsky sign can be positive in SJS/TEN, staph scalded skin syndrome, and pemphigus vulgaris
  • Time of onset is 1-3 after starting the offending drug
  • SCORTEN score is useful for determining prognosis
  • Early use of cyclosporine in patients with SJS/TEN has shown significant reduction in mortality.

DDx for cavitary lung lesions

  • Infection
    • Pyogenic (necrotizing pneumonia, septic emboli, lung abscess)
    • Atypical (MTB, fungi)
  • Autoimmune
    • GPA >> RA, sarcoid
  • Malignancy
    • Liquid (lymphoma, KS, lymphomatoid granulomatosis)
    • Solid (squamous, GU>GI)
  • Vascular
    • PE
  • Other
    • Foreign body granulomatosis

SJS/TEN (Steven Johnson vs toxic epidermal necrolysis)

  • < 10% = SJS, > 30% = TEN, in between = Overlap
  • Common causes
    • Sulfa drugs
    • Abx (PCN, quinolones)
    • AEDs
    • Allopurinol
    • Infx: Mycoplasma, graft-vs-host
    • Idiopathic
  • Risk factors
    • HIV (100x higher risk)
    • Genetics
      • There are a lot of them (check on uptodate for specific drugs) but a couple examples are:
        • HLA-B*58:01 (allopurinol)
          • Patients with this positive gene has higher risk for severe cutaneous hypersensitivity reaction to allopurinol including SJS and TEN. High risk Asian populations carrying this gene are Korean, Thai and Han Chinese.
        • HLA-B*15:02 is recommended before starting carbamazepine in Asians and South Asians
        • Cytochrome CYP2C19 polymorphism
    • Autoimmune disease
    • Malignancy
    • High doses and rapid infusion of medications
  • Clinical Presentation
    • 1-3 weeks after offending drug
    • Fever >39
    • Influenza-like symptoms (malaise, myalgias, arthralgias) x 1-3 days
    • Conjunctival itching or burning
    • Odynophagia
    • Cutaneous findings:
      • Acute onset macules over face, trunk, may form flaccid bullae
      • Nikolsky sign:
        • Positive when shear stress on the skin i.e. rubbing results in exfoliation. Indicates a pathology at the dermal/epidermal junction.
        • Positive in
          • SJS/TEN
          • Staphylococcal scalded skin syndrome
          • Pemphigus vulgaris
      • Asboe-Hansen sign (AKA bullae spread sign)
      • Mucous membrane involvement.
        • Eyes, mouth lesions
        • Respiratory sx
  • Prognosis:
    • SCORTEN score
    • Mortality with SJS is 10%, TEN 30%
  • Management
    • Supportive care for skin
    • Pain control
    • IV fluids
    • Prevention of vulvovaginal sequelae
    • Ocular management
      • Evaluate for loss of surface epithelium
      • Opthalmic therapy
        • Saline rinses to remove debris
        • Artificial tears
        • Topical steroids
        • If extensive sloughing, then amniotic membrane transplantation (prokera ring)
    • Adjunctive therapies
      • Steroids: may lead to higher rates of complications
      • IVIG: conflicting data
      • Cyclosporine: one large case series from Spain and two systematic reviews have shown that cyclosporine given at 3 to 5 mg/kg may slow the progression.  Inhibits T cell activation and thus prevents the production and release by cytotoxic T cell and natural killer cells of cytokines that could propagate SJS/TEN.
        • A study on 71 patients of whom 49 were treated with cyclosporine and 22 with other therapies found mortality rates were 10% and 32% respectively.  Expected mortality based on SCORTEN for the cyclosporine group was 24% and 29% in the other group.
        • A 2018 meta-analysis on 255 patients with TEN found that treatment with cyclosporine was associated with a 70% reduction in mortality risk
      • Plasmapharesis
      • Anti-TNF

Bonus info on gout:

  • Acute flare:
    • Steroids
    • NSAIDs
    • Colchicine (avoid in severe renal or hepatic impairment or with meds that inhibit CYP450 system)
  • Indications for urate-lowering therapy for chronic treatment
    • Frequent or disabling gout flares
    • Clinical or radiographic signs of joint damage
    • Tophaceous deposits in soft tissues or subchondral bone
    • Gout with renal insufficiency (CrCl<60)
    • Recurrent uric acid nephrolithiasis
    • Urinary acid excretion >1100 mg/day)
  • Goal uric acid is <6mg/dL
  • Agents for chronic management
    • Xanthine oxidase inhibitors
      • Allopurinol, lower dose for CKD3 or higher renal disease
      • Febuxostat, very expensive, cardiovascular and hepatic side effects
    • Uricosuric drugs: ineffective if CrCl<50. Can worsen kidney injury. Avoid use if GFR <30
      • Probenecid
      • Lesinurad
    • Uricase
      • Pegloticase, fast improvement of symptoms, contraindicated in G6PD deficiency

Varicella Pneumonia

Joe presented the case of a young man from Mexico with unknown immunization history who presented with acute onset of AMS, fevers, and a progressive vesicular rash, diagnosed with primary varicella infection (chickenpox!), now in the ICU with varicella pneumonia and likely varicella vasculitis induced stroke.


Clinical Pearls

  • Vaccinate your kids!
  • Two main VZV presentations are primary infection (chickenpox) and reactivation (shingles, disseminated zoster in immunocompromised individuals)
  • Varicella rash presents as vesicular lesions at varying stages.  Vesicular lesions at the same stage of development are concerning for smallpox.
  • The most common complication of primary VZV in adults is pneumonia.  Treatment is with IV acyclovir.
  • The most common neurologic complication of primary VZV is encephalitis.  No approved therapy exists.
  •  Isolation precautions for shingles is contact.  For disseminated zoster or chickenpox, make sure you patient is on contact and airborne precautions.

Differential for fever, rash, and pharyngitis:

  • Measles
  • Mono (due to EBV, CMV, toxo, HHV6)
  • Acute HIV
  • Parvovirus
  • Zoster
  • HSV
  • Mycoplasma

Fever and rash emergencies:

  • Meningococcemia
  • Subacute bacterial endocarditis
  • Rocky Mountain Spotted Fever
  • Necrotizing fasciitis
  • Toxic epidermal necrolysis
  • Toxic shock syndrome (staph aureus or GAS)

Varicella zoster (VZV)

  • Primary infection – chickenpox
    • Clinical manifestations:
      • Prodrome of fever, malaise, pharyngitis, loss of appetite
      • Rash is often pruritic and occurs in successive crops over days (new vesicle formation stops after 4 days). Vesicular lesions at varying stages on an erythematous base on the trunk, face, and extremities.
    • Diagnosis:
      • send swab (from ulcer base) for HSV PCR and DFA.  These have quick turn around time and high sensitivity.  Viral culture takes weeks and is less sensitive.
    • Most common complications
      • Children: skin infection
      • Adults:
        • Pneumonia (1/400 cases) with a mortality of 10-30%. In people requiring mechanical ventilation, mortality reaches 50%.
          • Risk factors for pneumonia development are cigarette smoking, pregnancy, immunosuppression, and male sex.
          • Develops 1-6 days after the appearance of rash
          • CXR usually with diffuse bilateral infiltrates with possible nodular component in early stages
          • Prompt administration of acyclovir has been associated with clinical improvement
        • Neurologic:
          • Encephalitis: acute cerebellar ataxia (more common in children), diffuse encephalitis (more common in adults)
            • No proven therapy once encephalitis occurs. Acyclovir has been used with anecdotal success
          • Transient focal deficits
          • Aseptic meningitis
          • Transverse myelitis
          • Vasculitis (medium to large vessel vasculopathy)
          • Hemiplegia
        • Hepatitis
          • More common in immunocompromised hosts and frequently fatal
        • Other
          • Diarrhea, pharyngitis, otitis media
    • Treatment
      • For healthy children <12 ⇒ nothing
      • For adults
        • if no complications, then oral valacyclovir (1g TID) or acyclovir (800 mg 5 times/day)
          • if immunocompromised ⇒ treat with IV acyclovir if active lesions present (10mg/kg q8h)
        • if complications
          • acyclovir IV 10mg/kg q8h for 7-10days
        • contact and airborne precautions!
  • Reactivation – shingles
    • Clinical manifestations –
      • Rash – most common location is thoracic and lumbar dermatomes
        • Localized, painful and restricted to a dermatome
        • Disseminated if > 3 contiguous dermatomes or 2 dermatomes on separate parts of the body, painful
      • Acute neuritis – 75% of patients have pain/burning/throbbing prior to onset of rash
    • Complications in immunocompetent hosts –
      • post-herpetic neuralgia (most common), superficial skin infections, ocular complications (acute retinal necrosis and zoster ophthalmicus), motor neuropathy, meningitis, Ramsay hunt syndrome (zoster oticus)
    • Treatment
      • For patient with localized disease presenting <72 hours after clinical symptom onset, treat with oral acyclovir, valacyclovir, or famciclovir
      • For patient with localized disease presenting >72 hours after disease onset, then monitor
      • Pregnant women, treat with acyclovir
      • Disseminated disease, treat with IV acyclovir

 

Leukocytoclastic vasculitis

Today, we talked about the case of a middle-aged man with history of diabetes, HTN, and A fib who presented with acute onset of progressive painful palpable purpura on his extremities, found to be cutaneous small vessel vasculitis on skin biopsy!


Clinical Pearls

  • Purpura implies problem at the level of vessel.  It can be divided into
    • Non-palpable purpura: petechiae (<3mm) or ecchymoses (>3 mm) and are usually associated with disorders of coagulation and platelets.
    • Palpable purpura: suggests inflammation and possible vasculitis.

Nomenclature:

  • Cutaneous small vessel vasculitis: disease limited to skin without any systemic vasculitis or glomerulonephritis
  • LCV: histopathologic term defining vasculitis of small vessels
  • Hypersensitivity vasculitis: small vessel necrotizing vasculitis
  • Immune complex small vessel vasculitis: associated with immune complex and/or complement deposition. If limited to skin, this is identical to cutaneous small vessel vasculitis. If not limited to skin, then other etiologies like cryo, SLE, Sjogren, RA, anti-GBM, IgA, etc.

Approach to purpura

Approach to purpura

  • Hypersensitivity (in the normal complement category of vasculitis) can result from medications/drugs as well as certain conditions such as HIV.
    • Numerous meds can cause LCV including some common ones such penicillins, cephalosporins, sulfonamides (including most loop and thiazide-type diuretics), phenytoin, and allopurinol have been most often implicated

Cutaneous small vessel vasculitis:

Clinical presentation:

  • Palpable purpura
  • + petechiae
  • Lesions can coalesce, ulcerate or be surrounded by hemorrhagic bullae
  • No visceral organ involvement in CSVV. However, it can occur later in the disease course.

Diagnosis:

  • Start with checking serum complement levels to guide your need for further laboratory work up!
  • Skin biopsy

Management and Prognosis:

  • Usually self limited and resolved within 2-4 weeks
  • If uncomplicated:
    • NSAIDs
    • Antihistamines
    • Rest, elevate, compression stockings
  • If complicated (presence of hemorrhagic blisters, cutaneous necrosis, or ulceration can lead to secondary infections, chronic wounds, and scarring)
    • Systemic glucocorticoids (oral steroids): pred 0.5 mg/kg of ideal body weight until new lesion formation ceases, then taper over 3-6 weeks
    • If relapse with prednisone: then colchicine or dapsone
    • If refractory: then azathioprine, methotrexate, and MMF

Example of palpable purpura with hemorrhagic blisters:

LCV skin example

Acute Rheumatic Fever

Today, we talked about the very interesting case of a middle-aged man who presented with acute migrating oligoarthritis, found to be febrile with an inflammatory synovial fluid and elevated ASO titers consistent with acute rheumatic fever!


Clinical Pearls

  • Nonsuppurative manifestations of GAS infection include acute rheumatic fever (ARF), acute GN, and Scarlet fever.
  • Use the modified Jones Criteria to help you diagnose ARF and treat early if high suspicion for the disease (do not wait for titers to come back).
  • Late complications of ARF include rheumatic heart disease (10-20 years after infection) and Jaccoud arthropathy.
  • Treatment of ARF involves NSAIDs for arthritis, PCN G IM x 1 dose for acute presentation and then monthly for prophylaxis, and patient education about oral hygiene to prevent endocarditis and need for prophylaxis before invasive procedures.

Differential diagnosis for a migratory arthritis

  • Rheumatic fever
  • Infective endocarditis
  • Vasculitis (IgA, cryo, ANCA associated)
  • SLE 
  • Acute leukemia
  • Serum sickness
  • Viral arthritis
  • Bacteremia (staph, strep, mening/gonococcal)
  • Pulmonary infections (mycoplasma, histoplasma)
  • Lyme
  • Whipple’s

Nonsuppurative complications of GAS infection

  • ARF
  • Scarlet fever
  • Acute GN

Rheumatic fever 

  • Nonsuppurative sequela that occurs 2-4 weeks after GAS pharyngitis
  • Epi
    • More common in children 5-15 years of age
    • More common in resource limited settings
  • Pathogenesis:
    • Poorly understood, ?molecular mimicry
  • Clinical manifestations:
    • Two primary manifestations of disease

Two manifestations of ARF

(Table above from UpToDate)

  • Late sequelae
    • Rheumatic heart disease (10-20 years after infection), primary involves the mitral valve >aortic valve.
      • Leading cause of cardiovascular death in the first 5 decades of life in resource limited settings
    • Jaccoud arthropathy
  • Diagnosis:
    • Revised Jones criteria (joint and cardiac manifestations can only be counted once).
      • Major
        • Carditis and valvulitis (clinical or subclinical) – 50-70%
          • Usually pancarditis. Valvulitis especially of mitral and aortic valves, shown as regurg on echo.
          • Carey Coombs murmur: short mid-diastolic murmur heard loudest at the apex
        • Arthritis (migratory, involving large joints) – 35-66%, earliest symptom
          • Several joints affected in quick succession, each inflamed for a day or two to one week. Most common are knees, ankles, elbows, and wrists.
        • CNS involvement (Sydenham chorea) – 10-30%
        • Subcutaneous nodules – 0-10%
        • Erythema marginatum – <6% 
      • Minor
        • Arthralgia
        • Fever >38.5
        • Elevated acute phase reactants (ESR, CRP)
        • Prolonged PR interval on EKG
      • Diagnosis requires evidence of prior GAS infection plus:
        • 2 major OR
        • 1 major + 2 minor criteria OR
        • 3 minor criteria (only if patient has history of prior episode of ARF)
      • In a high prevalence setting, slightly modified criteria are used.
    • Labs:
      • Prior GAS infection through either
        • Throat culture
        • Positive rapid strep antigen test
        • Elevated or rising ASO titers
      • Treatment
        • Goals
          • Symptomatic relief of acute disease manifestations
            • Arthritis: NSAIDs
            • Carditis: if severe, heart failure treatments
          • Eradication of GAS
            • IM PCN G benzathine x 1
            • Contacts (throat culture test and treat if positive)
          • Ppx against future GAS infection to prevent progression of cardiac disease
            • PCN G IM once a month
            • For 5 years or until 21 years of age (whichever is longer)
            • If ARF with carditis and residual heart disease
              • 10 years or until 40 years, sometimes even lifelong
            • Education
              • Oral health
              • Ppx before any invasive procedures

On rhabdo and myopathies – 10/9/18

Thanks to Cameron and Adam for presenting the case of a middle aged man with no significant PMH who presented with diffuse myalgias and chronic progressive proximal muscle weakness, found to have a CK >12k and EMG findings concerning for an inflammatory myopathy, awaiting muscle bx for diagnosis.


Clinical Pearls

  • Rhabdomyolysis literally means dissolution of skeletal muscle and has a broad differential outside of the typical traumatic or exertional processes associated with it see below).
  • The four main inflammatory myopathies are dermatomyositis, polymyositis, inclusion body myositis, and necrotizing autoimmune myositis.
  • Polymyositis is rare and a diagnosis of exclusion after the other three main inflammatory myopathies have been investigated.
  • Overall, the prognosis of inflammatory myopathies is good with appropriate treatment.  The exception is inclusion body myositis which is a progressive disorder without any effective therapy.
  • Pigment nephropathy can occur with rhabdo regardless of the underlying etiology especially in patients with CK >5000.  Aggressive IV hydration to lower CK levels is important to reduce the risk of kidney injury.

Rhabdomyolysis:

DDx:

  • Traumatic
    • Crush injuries, surgery, prolonged compression from immobility or coma
  • Non-traumatic
    • Exertional:
      • Normal muscle: strenuous exercise, heat stroke, seizures, hyperkinetic states
      • Abnormal muscle: metabolic myopathies, mitochondrial myopathies, malignant hyperthermia, NMS
    • Non-exertional
      • Alcoholism
      • Drugs and toxins: lipid-lowering drugs (fibrates, statins), alcohol, heroin, cocaine, meth, colchicine
      • Infections: influenza, coxsackie, EBV, HIV, legionella
      • Electrolyte abnormalities: hypokalemia, hypophosphatemia, hypocalcemia
      • Endocrinopathies: DKA, HHS, hypothyroidism, vitamin D deficiency
      • Inflammatory myopathies (rare)
      • Paraneoplastic
      • Miscellaneous

Inflammatory myopathies

Largest group of potentially treatable myopathies in children and adults.

  • Four subtypes: distinguishing which process is important because each subtype has a different prognosis and response to therapy
    • DM
      • Anti-Mi-2, anti-MDA-5, anti-TIF-1, anti-NXP-2
    • PM
      • Rare, often misdiagnosed
      • Dx of exclusion
    • Necrotizing autoimmune myositis
      • More common than PM
      • Occurs alone or after viral infections or in association with cancer, CTD, or post-statin
      • Anti-SRP or anti-HMGCR
      • Highest CK level
    • Inclusion body myositis
      • Most common in people >50
      • 7.9 cases/million in the US
      • Distal muscles impacted first
      • Facial muscles impacted
      • Muscle atrophy occurs earlier than in others
      • Extramuscular manifestations are uncommon
      • Dysphagia occurs in >50%
      • Muscle atrophy is common
      • Lowest CK level
  • Up to 30% of patients with DM or PM have a constellation of clinical findings termed “antisynthetase syndrome”
    • Acute disease onset
    • Constitutional symptoms (fever, weight loss)
    • Myositis
    • Raynaud’s
    • Mechanic’s hands
    • Non-erosive arthritis
    • ILD
    • Labs show antibodies to tRNA synthetase enzymes (anti-Jo-1)
  • Extramuscular manifestations
    • systemic symptoms
    • cardiac arrhythmias or ventricular dysfunction
    • pulmonary complications (ILD)

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Table above adapted from this and this review article by NEJM.