Systemic Diseases
Neurosarcoidosis & Systemic Autoimmune Diseases
What You'll Learn
- Neurosarcoidosis: Non-caseating granulomas; cranial neuropathies (facial nerve #1) and hypothalamic–pituitary dysfunction are the hallmark presentations; tissue confirmation of systemic or nervous-system sarcoidosis remains central; both serum and CSF ACE have limited sensitivity and variable specificity — supportive only, not rule-in/rule-out
- Neuro-Behçet: Oral + genital ulcers with CNS involvement — parenchymal (brainstem predilection) vs. non-parenchymal (cerebral venous sinus thrombosis); pathergy test and HLA-B51 support diagnosis
- Neuropsychiatric SLE: 19 ACR-defined syndromes; distinguish inflammatory (immunosuppression) vs. thrombotic (anticoagulation for antiphospholipid syndrome); anti-ribosomal P antibodies correlate with psychosis
- Sjögren syndrome: Peripheral neuropathy (sensory ganglionopathy most characteristic) > CNS involvement. Per 2016 ACR/EULAR criteria, anti-SSA/Ro and minor salivary gland biopsy with focal lymphocytic sialadenitis (focus score ≥1) carry the key classification weight; isolated anti-SSB/La was removed (limited specificity)
- IgG4-related disease: Hypertrophic pachymeningitis, orbital pseudotumor, hypophysitis; storiform fibrosis + IgG4+ plasma cells on tissue biopsy; rituximab is highly effective
- Susac syndrome: Triad of encephalopathy + branch retinal artery occlusion (BRAO) + sensorineural hearing loss; central callosal “snowball” lesions on MRI (vs. MS peripheral callosal lesions)
- Key board principle: Each systemic autoimmune disease has a characteristic neurological signature — matching the pattern to the disease is the fastest path to the correct answer
HighYield Pearls
- NPSLE psychosis & anti-ribosomal P: Anti-ribosomal P antibodies correlate with lupus psychosis. In the 2019 EULAR/ACR classification, a positive ANA is the high-sensitivity entry criterion; anti-dsDNA and anti-Sm are specific immunologic criteria that support diagnosis but anti-dsDNA is not mandatory. NPSLE attribution requires excluding mimics and correlating the syndrome with active SLE; anti-NMDAR (anti-N2A/N2B) tracks cognitive dysfunction
- APS — warfarin standard, DOACs avoided in high-risk APS: Vitamin K antagonists (warfarin INR 2–3) remain standard for thrombotic APS. Avoid DOACs in triple-positive APS (LAC + anticardiolipin + β2-glycoprotein I) and in arterial APS (TRAPS trial showed rivaroxaban inferior in triple-positive); selected lower-risk venous APS scenarios are more nuanced and specialist-dependent
- Catastrophic APS quadruple therapy: Multi-organ failure within days → IVIG + high-dose steroids + plasma exchange (PLEX) + anticoagulation; livedo reticularis + stroke = think Sneddon syndrome
- Sjögren sensory ganglionopathy: Non-length-dependent sensory loss + pseudoathetosis + areflexia + sensory ataxia → dorsal root ganglion targeting; lip biopsy focus score ≥1 confirms; anti-Ro/La
- Neurosarcoid biopsy beats ACE: Serum ACE has only ~60% sensitivity — never rule out with a normal ACE; biopsy from accessible site (skin, conjunctiva, lymph node) + FDG-PET to find target; bilateral facial palsy is the classic clue
- Neuro-Behçet parenchymal vs CVT: Brainstem-predominant inflammatory lesion (mesodiencephalic) = parenchymal; cerebral venous sinus thrombosis = non-parenchymal; oral + genital aphthae + uveitis + pathergy + HLA-B51
- RA atlantoaxial subluxation: Cervical pannus + odontoid erosion → cord compression and myelopathy; flexion-extension cervical imaging before any intubation in long-standing RA
- IgG4 pachymeningitis: Hypertrophic dural thickening + cranial neuropathies + hypophysitis + orbital pseudotumor; storiform fibrosis + obliterative phlebitis + IgG4⁺ plasma cells; rituximab is highly effective
- GPA vs EGPA vs PAN: GPA = c-ANCA/PR3 + sinus/lung/kidney + pachymeningitis; EGPA = asthma + eosinophilia + p-ANCA/MPO (40%) + mononeuritis multiplex; PAN = ANCA-negative + HBV + medium-vessel + nerve/muscle biopsy
- Exclude vasculitis BEFORE immunosuppression: Always pursue biopsy (nerve, muscle, brain, dura) when vasculitis is on the differential — empiric steroids can blind the diagnosis and delay definitive therapy
🔍 Quick ReferenceClinical · Labs / imaging · Treatment
Clinical syndrome by disease
- Young woman + malar rash + psychosis + seizures → Neuropsychiatric SLE
- Recurrent miscarriage + arterial & venous thrombosis + livedo reticularis → Antiphospholipid syndrome
- Livedo racemosa + recurrent stroke (no other APS features) → Sneddon syndrome
- Multi-organ failure within days + thrombocytopenia + microangiopathy → Catastrophic APS (CAPS)
- Sicca symptoms + sensory ataxia + pseudoathetosis + areflexia → Sjögren sensory ganglionopathy
- Bilateral facial palsy + uveitis + parotid swelling + fever → Heerfordt syndrome (neurosarcoidosis)
- Oral + genital aphthous ulcers + uveitis + brainstem lesion → Neuro-Behçet
- Long-standing RA + neck pain + Lhermitte + myelopathy → Atlantoaxial subluxation with cervical pannus
- Asthma + eosinophilia + mononeuritis multiplex + cardiomyopathy → EGPA (Churg-Strauss)
- Encephalopathy + branch retinal artery occlusion + sensorineural hearing loss → Susac syndrome
Labs / imaging
- Anti-ribosomal P antibody → Lupus psychosis
- Triple positive: LAC + anticardiolipin + β2-glycoprotein I → High-risk antiphospholipid syndrome
- Anti-SSA/Ro + lip biopsy focal lymphocytic sialadenitis (focus score ≥1) ± Schirmer abnormal → Sjögren syndrome (2016 ACR/EULAR; isolated anti-SSB/La is NO longer a serologic criterion)
- Anti-Scl-70 (topoisomerase I) / anti-centromere → Scleroderma (diffuse / limited)
- Anti-U1-RNP (high titer) → Mixed connective tissue disease
- Dorsal subpial “trident sign” on axial cord MRI + non-caseating granulomas → Neurosarcoid myelitis
- Basal leptomeningeal enhancement + hypothalamic-pituitary involvement + low CSF glucose → Neurosarcoidosis
- Central callosal “snowball” lesions on MRI → Susac syndrome (vs peripheral callosal in MS)
- c-ANCA / anti-PR3 + sinus + lung + kidney + pachymeningitis → GPA (Wegener)
- p-ANCA / anti-MPO + asthma + eosinophilia → EGPA (Churg-Strauss)
- HBsAg positive + medium-vessel beading on angiography + ANCA-negative → Polyarteritis nodosa
- HLA-B51 + positive pathergy test → Behçet disease
- Storiform fibrosis + obliterative phlebitis + IgG4⁺ plasma cells on biopsy → IgG4-related disease
Treatment / pearls
- Warfarin INR 2–3 (NOT rivaroxaban — TRAPS trial) → Triple-positive antiphospholipid syndrome
- IVIG + steroids + plasma exchange + anticoagulation → Catastrophic APS
- Steroids + cyclophosphamide or MMF → Severe NPSLE / lupus nephritis
- Steroids + methotrexate/azathioprine; infliximab for refractory → Neurosarcoidosis
- Rituximab is highly effective (steroid-responsive but relapses) → IgG4-related pachymeningitis
- Rituximab + cyclophosphamide + steroids → GPA / severe ANCA-associated vasculitis
- Mepolizumab (anti-IL-5) as steroid-sparing → EGPA (Churg-Strauss)
- Tocilizumab (anti-IL-6) → Giant cell arteritis (steroid-sparing)
- Anti-TNF (infliximab/adalimumab) + steroids + azathioprine → Neuro-Behçet (parenchymal)
- Rituximab + IVIG → Sjögren-associated CNS disease / ganglionopathy
- Flexion-extension cervical MRI before intubation → Long-standing RA (atlantoaxial subluxation risk)
- Biopsy gold standard — never rely on ACE alone → Neurosarcoidosis workup
Neurosarcoidosis
Overview & Pathology
- Definition: CNS/PNS involvement by sarcoidosis — a multisystem granulomatous disease of unknown etiology
- Pathology: Non-caseating (non-necrotizing) granulomas composed of epithelioid histiocytes, multinucleated giant cells, and surrounding lymphocytes
- Epidemiology: ~5–15% of sarcoidosis patients develop neurological involvement; may be the presenting feature in up to 50% of neurosarcoidosis cases
- Predilection: African Americans, women, age 25–50 years
Clinical Manifestations
| Manifestation | Frequency | Key Features |
|---|---|---|
| Cranial neuropathies | 50–70% | CN VII (facial nerve) #1 — may be bilateral; CN II (optic nerve) #2 — optic neuritis, papilledema; any CN can be affected |
| Leptomeningeal disease | 10–20% | Basal leptomeningeal enhancement on MRI; chronic meningitis with CSF lymphocytic pleocytosis |
| Hypothalamic–pituitary | 10–15% | Diabetes insipidus (most common endocrine manifestation); hyperprolactinemia; panhypopituitarism |
| Myelopathy | 5–10% | Dorsal subpial enhancement (“trident sign” on axial MRI); longitudinally extensive; mimics NMOSD |
| Peripheral neuropathy | 15–20% | Small fiber neuropathy most common; polyradiculopathy; mononeuritis multiplex |
| Parenchymal mass | 5–10% | Ring-enhancing or solid lesion; mimics tumor or abscess |
| Hydrocephalus | 5–10% | Communicating (leptomeningeal) or obstructive (mass lesion) |
Heerfordt Syndrome (Uveoparotid Fever)
- Classic tetrad: Parotid gland enlargement + anterior uveitis + facial nerve palsy + fever
- Pathognomonic for sarcoidosis — highly specific clinical presentation
- May be the initial presentation of systemic sarcoidosis
💎 Board Pearl
- Bilateral facial palsy + uveitis = sarcoidosis until proven otherwise. Differential for bilateral CN VII palsy: Lyme, sarcoidosis, GBS (including Miller Fisher), HIV / HIV seroconversion, leukemic / lymphomatous infiltration, basal meningitis (TB, syphilis), and bilateral Bell palsy
- Diabetes insipidus + leptomeningeal enhancement on MRI = think neurosarcoidosis (also consider lymphoma, TB, and carcinomatous meningitis)
- Trident sign on axial spinal MRI = dorsal subpial gadolinium enhancement — characteristic of neurosarcoidosis myelopathy
Diagnostic Workup
| Test | Findings | Pearls |
|---|---|---|
| Serum ACE | Elevated in ~60% of systemic sarcoidosis | Low sensitivity (~60%) and poor specificity; normal ACE does NOT exclude diagnosis; false positives with diabetes, hyperthyroidism, lymphoma |
| Chest CT | Bilateral hilar lymphadenopathy (BHL) in ~90% of sarcoidosis | BHL is the most common thoracic finding; absence significantly lowers probability but does not exclude |
| Gallium-67 / PET scan | “Panda sign” (lacrimal + parotid uptake); “Lambda sign” (bilateral hilar + right paratracheal uptake) | FDG-PET largely replacing gallium; useful for identifying biopsy sites |
| CSF | Lymphocytic pleocytosis (50–70%), elevated protein (50–70%), low glucose (10–20%), CSF ACE may be elevated | CSF ACE has limited sensitivity and variable specificity for neurosarcoidosis; supportive in context but should NOT be used as a rule-in/rule-out test. Tissue confirmation of systemic or nervous-system sarcoidosis remains central when feasible |
| MRI brain/spine | Leptomeningeal enhancement (basal predominance), parenchymal lesions, hypothalamic/infundibular thickening, cranial nerve enhancement | Leptomeningeal pattern is the most suggestive imaging feature |
| Biopsy | Non-caseating granulomas = gold standard | Target most accessible tissue: lymph node > lung > skin > meninges/brain; must exclude TB, fungal infection, foreign body |
Zajicek Diagnostic Criteria
| Category | Criteria |
|---|---|
| Definite | Compatible clinical presentation + positive nervous system biopsy (non-caseating granulomas) + exclusion of other causes |
| Probable | Compatible clinical presentation + evidence of CNS inflammation (CSF/MRI) + positive systemic biopsy (non-CNS tissue) + exclusion of other causes |
| Possible | Compatible clinical presentation + exclusion of other causes + no tissue confirmation (supportive labs: ACE, chest imaging, etc.) |
💎 Board Pearl
- Serum ACE is a poor screening test — sensitivity only ~60%, and many false positives; never rely on a normal ACE to rule out neurosarcoidosis
- Always get a chest CT — bilateral hilar lymphadenopathy is present in ~90% and provides a safer biopsy target than CNS tissue
- “Probable” neurosarcoidosis is the most common working diagnosis — CNS biopsy is invasive and often avoided if systemic disease is confirmed
Treatment
| Line | Agent(s) | Details |
|---|---|---|
| First-line | Corticosteroids | IV methylprednisolone 1 g/day × 3–5 days for acute/severe → oral prednisone taper over months; most patients require prolonged therapy |
| Steroid-sparing | Methotrexate, azathioprine, mycophenolate mofetil | Methotrexate is the most commonly used steroid-sparing agent; typically added within 2–3 months to reduce steroid burden |
| Refractory | Infliximab, adalimumab (anti-TNF-α) | Infliximab most studied; effective for CNS and PNS disease; monitor for infection, demyelination |
- Prognosis: ~30% monophasic (self-limited); ~30% relapsing–remitting; ~30% chronic progressive despite therapy
- Mortality: 5–10% in neurosarcoidosis; worse with parenchymal disease, hydrocephalus, chronic meningitis
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