C1q Deficiency

Other names
Types
Causes
Symptoms
Diagnostic tests
Non-pharmacological treatments (therapies & others)
Drug treatments
Dietary molecular supplements
Immunity-booster / regenerative / stem-cell” therapies
Procedures/surgeries (why they’re done)
Prevention tips
When to see a doctor urgently
What to eat and what to avoid
Frequently asked questions

C1q deficiency is a very rare inherited immune problem where the body makes too little—or none—of a protein called C1q. C1q is the “starter” of the classical complement pathway, a group of blood proteins that help fight germs and clean up dead cells and immune complexes. When C1q is missing or not working, the immune system struggles to clear these materials. This failure can trigger autoimmune disease (especially lupus) and increase risk of serious bacterial infections, particularly from encapsulated bacteria. In many people, symptoms begin in childhood. The condition is usually passed down in an autosomal recessive pattern and can be caused by harmful variants in C1QA, C1QB, or C1QC genes. GARD Information Center+2PMC+2

C1q deficiency is an inherited problem in the very first step of the classical complement pathway. When C1q is absent or very low, the body clears dying cells and immune complexes poorly. That often triggers lupus-like autoimmunity (skin, kidneys, brain) and raises infection risk. Case series and reviews consistently link C1q deficiency with early, severe, SLE-like disease; small reports describe symptom control with IVIG, hydroxychloroquine, and—rarely—curative allogeneic stem-cell transplant or periodic C1q replacement using fresh frozen plasma (FFP). PMC+4PMC+4PMC+4

C1q deficiency is one of the strongest known genetic risk factors for systemic lupus erythematosus (SLE). Upwards of most individuals with complete C1q deficiency develop lupus-like disease, often early in life. At the same time, people are prone to repeated infections of the lungs, sinuses, ear, brain coverings (meningitis), and skin. PMC+2EULAR+2

Other names

Doctors and databases may use these names:

Hereditary C1q deficiency or C1q complement deficiency
Immunodeficiency due to classical pathway component deficiency (C1q subtype)
C1QD; C1qA/C1qB/C1qC deficiency (gene-specific)
These labels all point to the same clinical problem: very low or absent C1q function. Orpha+2NCBI+2

Types

Complete (quantitative) deficiency – C1q protein is absent or nearly absent in the blood. This is the classic, severe form and is most tightly linked to early, severe lupus-like disease and serious infections. NCBI+1
Dysfunctional (qualitative) C1q – The protein is present but doesn’t work properly because of structural changes (missense or other variants). Illness may be similar but sometimes starts later or shows variable severity. NCBI
Gene-specific subtypes – Harmful variants in C1QA, C1QB, or C1QC. Identifying the exact gene helps with genetic counseling for families. GARD Information Center+1

Note: Doctors also see acquired low C1q in some autoimmune or protein-losing conditions, but “C1q deficiency” usually means the inherited inborn error described above. NCBI

Causes

When we say “cause,” we mostly mean why C1q is missing or not working. For an inherited disorder, “causes” include the specific genetic changes and a few medical situations that further drop complement levels.

Autosomal recessive variants in C1QA – both gene copies altered → no/low C1q. GARD Information Center
Autosomal recessive variants in C1QB – similar effect. GARD Information Center
Autosomal recessive variants in C1QC – similar effect. GARD Information Center
Nonsense/frameshift variants – produce truncated proteins that are degraded. NCBI
Missense variants – protein made but misfolded or cannot bind correctly → poor function. NCBI
Promoter/splice variants – reduce C1q production. NCBI
Consanguinity in some families – increases chance both parents carry the same rare variant. Turkish Journal of Pediatrics
Ineffective clearance of apoptotic cells (downstream mechanism) – not the root cause, but explains why variants lead to lupus. PMC
Immune complex accumulation (mechanism) – drives inflammation and autoimmunity. Primary Immune
Acquired complement consumption during active autoimmune disease – temporarily lowers levels. NCBI
Severe infections – can consume complement proteins during acute illness. NCBI
Protein-losing states (e.g., nephrotic syndrome) – can lower complement protein levels. NCBI
Severe liver synthetic dysfunction – complement proteins are made in the liver; bad liver failure can reduce them. NCBI
Anti-C1q antibodies in some autoimmune settings – bind C1q and may alter function/measurement (more often a marker than a root cause). PMC
Rare copy-number changes in C1Q genes – uncommon but reported. NCBI
Post-translational processing defects (rare) – abnormal assembly of the C1q hexamer. NCBI
Novel/private family variants – many families have unique mutations. Turkish Journal of Pediatrics
Compound heterozygosity – two different harmful variants, one on each copy. NCBI
Founder effects in small populations – one ancient variant appears more often locally. Turkish Journal of Pediatrics
Unknown/undetected genetic mechanisms – very rare cases still being studied. PubMed

Symptoms

Lupus-like rash – a red, sometimes “butterfly-shaped” rash on the face or other skin areas because the body attacks its own tissues. This is common and may appear in childhood. PMC+1
Photosensitivity – rashes or flares after sun exposure because UV-injured skin cannot be cleared well. PMC
Mouth or nose ulcers – small, painful sores that reflect autoimmune activity. PMC
Arthritis/arthralgia – painful, swollen joints due to immune complex inflammation. PMC
Kidney inflammation (glomerulonephritis) – blood or protein in urine and swelling; a key organ risk. GARD Information Center
Neuro-psychiatric problems – seizures, headaches, or mood and thinking changes during lupus-like brain involvement. PMC
Recurrent ear, sinus, or lung infections – because complement helps opsonize (tag) bacteria for killing. NCBI
Meningitis – infection of the brain coverings, sometimes caused by Neisseria or other encapsulated bacteria. ScienceDirect
Skin infections/ulcers – impaired clearance allows bacteria to persist and skin to inflame. NCBI
Fever and fatigue – from ongoing inflammation or active infection. PMC
Lymph node or spleen enlargement – immune system activation can enlarge these organs. PMC
Serositis (chest/abdominal lining pain) – inflammation of the heart or lung lining causing chest pain or shortness of breath. PMC
Hair loss during flares – autoimmune activity can thin hair. PMC
Delayed growth or poor weight gain in children – repeated infections and chronic inflammation can slow growth. Frontiers
Raynaud-like color changes in fingers (some cases) – small vessel reactivity during autoimmune activity. PMC

Diagnostic tests

A) Physical examination (bedside assessment)

Full skin check – doctors look for butterfly rash, discoid lesions, vasculitic spots, or infected areas; patterns hint at lupus-like disease plus infection risk. PMC
Joint exam – checking swelling, warmth, and movement helps grade arthritis from autoimmunity. PMC
Vital signs and meningitis screen – fever, neck stiffness, headache, and light sensitivity suggest dangerous infection needing urgent care. ScienceDirect
Kidney/edema check – leg or facial swelling and high blood pressure can be clues to lupus nephritis. GARD Information Center
Neurologic exam – strength, sensation, reflexes, and mental status to detect seizures or brain involvement of lupus-like disease. PMC

B) Manual/bedside tests (simple clinical maneuvers)

Urine dipstick at the bedside – quick check for blood and protein, which suggests kidney inflammation. A lab urinalysis follows. PMC
Joint range-of-motion testing – documents arthritis severity and function. PMC
Phototesting history + sun-exposure diary – practical way to link rashes to sunlight. PMC
Pain scales and fever charts – track flares or infection patterns over time. Frontiers
Bedside neurological screening (e.g., mini-cog) – simple tests to flag cognitive issues during flares. PMC

C) Laboratory and pathological tests

Total classical complement function (CH50) – often absent in C1q deficiency because the classical pathway cannot activate; this is a key screening test. NCBI
C1q antigen level – measures how much C1q protein is present; near-zero suggests complete deficiency. Orpha
Functional C1 assay – shows whether C1 complex (C1q/r/s) works; helps distinguish quantitative vs qualitative defects. Orpha
C2 and C4 levels – often low in classical pathway defects or during consumption; patterns guide the work-up. NCBI
Autoantibody panel (ANA, anti-dsDNA, anti-C1q) – supports lupus-like disease; anti-C1q can appear in some autoimmune settings. PMC
CBC and inflammatory markers (ESR/CRP) – show anemia, low platelets, or inflammation during flares or infections. NCBI
Blood/CSF cultures in suspected infection – identify bacteria like Neisseria meningitidis, Streptococcus pneumoniae, or Haemophilus influenzae. Frontiers
Kidney tests (urinalysis, protein/creatinine ratio; kidney biopsy if needed) – confirm and grade glomerulonephritis. GARD Information Center
Genetic testing of C1QA, C1QB, C1QC – confirms the inherited diagnosis; helps family counseling and future planning. Orpha
Newer research panels for inborn errors of immunity – broader sequencing when the presentation is complex or unclear. PubMed

D) Electrodiagnostic tests (used when symptoms suggest)

EEG – if seizures or altered consciousness occur during neuro-lupus, EEG helps detect abnormal brain activity. PMC
ECG – chest pain or serositis may need heart rhythm checks; inflammation can affect the heart lining. PMC
Nerve conduction/electromyography (EMG) – rarely used, but helpful if neuropathy or myositis is suspected during autoimmune flares. PMC

E) Imaging tests

Chest X-ray – looks for pneumonia or pleural effusion in infections or serositis. Frontiers
Brain MRI – evaluates seizures, headaches, or cognitive changes to detect neuro-inflammation. PMC
Renal ultrasound – supportive imaging when kidney involvement is suspected. Biopsy remains the gold standard when needed. GARD Information Center
Echocardiogram – checks fluid around the heart or heart function if symptoms suggest serositis or myocarditis. PMC
CT/MRI for deep infections – used when severe infection is suspected in sinuses, chest, abdomen, or bones. Frontiers

Non-pharmacological treatments (therapies & others)

Each item includes what it is, purpose, and simple mechanism.

Strict sun/UV protection. Purpose: prevent lupus-like rashes and flares. Mechanism: UV light triggers skin cell damage and immune activation; broad-spectrum SPF ≥ 30, clothing, hats, shade reduce UV-driven inflammation. American Academy of Dermatology+2American Cancer Society+2
Vaccination up-to-date (pneumococcal, meningococcal, influenza, COVID-19 as indicated). Purpose: lower serious infection risk. Mechanism: primes adaptive immunity; especially important if future immunosuppressants are used. CDC+3CDC+3CDC+3
Early infection plan. Purpose: spot infections fast. Mechanism: teach “fever action plan,” prompt cultures/antibiotics because complement defects blunt opsonization. (Background and CDC altered-immunity vaccination guidance.) CDC
Regular kidney monitoring. Purpose: catch lupus nephritis early. Mechanism: periodic urine protein, creatinine; biopsy when criteria met. KDIGO+1
Dermatology care routines. Purpose: control photosensitive rash. Mechanism: gentle cleansers, topical agents, UV avoidance to calm cutaneous autoimmunity. (Photosensitivity guidance aligns with UV sources above.) American Academy of Dermatology
Pregnancy planning & counseling. Purpose: reduce flare/complication risk. Mechanism: pre-conception disease control, safe meds, vaccination review; antimalarial continuation when appropriate per SLE standards. (EULAR SLE framework.) PubMed
Bone health habits. Purpose: offset steroid-related loss. Mechanism: weight-bearing exercise, calcium/vitamin D as needed, DEXA per risk. (General SLE and steroid guidance.) PubMed
Cardiometabolic risk reduction. Purpose: lower long-term CV risk heightened in SLE-like states. Mechanism: stop smoking, manage BP, lipids, weight, exercise. (EULAR principles.) PubMed
Stress & sleep management. Purpose: reduce flare triggers and fatigue. Mechanism: CBT-I or mindfulness to lower stress-mediated cytokine surge seen in autoimmune disease frameworks. (General SLE recommendations.) PubMed
Infection exposure hygiene. Purpose: fewer respiratory/GI infections. Mechanism: hand hygiene, avoid sick contacts during high-dose immunosuppression windows. (CDC altered-immunity concepts.) CDC
Sun-protective clothing with UPF rating. Purpose: reliable UV barrier. Mechanism: tight-weave fabrics with UPF ≥ 50 block most UV. MD Anderson Cancer Center
Kidney-friendly lifestyle (if nephritis). Purpose: protect kidneys. Mechanism: limit excess salt, control BP, avoid NSAID overuse; follow nephrology diet advice alongside drug therapy. (KDIGO LN.) KDIGO
Medication adherence coaching. Purpose: stable control and fewer flares. Mechanism: reminders and simple dosing plans improve steady immunomodulation (SLE principle). PubMed
Photoprotection education for children. Purpose: early prevention. Mechanism: child-friendly sunscreen use and shade habits to curb pediatric photosensitive flares. CDC
Safe exercise program. Purpose: maintain strength, reduce fatigue. Mechanism: moderate aerobic + resistance improves inflammation markers in autoimmune illness. (Guideline-based SLE lifestyle.) PubMed
Skin biopsy when needed. Purpose: confirm cutaneous lupus vs. infection. Mechanism: histology/direct immunofluorescence guides therapy intensity. (Dermatology practice within SLE care.) PubMed
Sun-safe workplaces/school letters. Purpose: accommodations for indoor breaks and protective clothing. Mechanism: reduce UV exposure at peak hours. American Cancer Society
Dental prevention. Purpose: lower infection portals. Mechanism: routine dental hygiene reduces bacteremia risk when immunosuppressed. (General altered-immunity hygiene.) CDC
Travel vaccines/timing advice. Purpose: safe travel. Mechanism: schedule inactivated vaccines before trips; consider meningococcal/pneumococcal status; avoid live vaccines when immunosuppressed. CDC
Care coordination (rheumatology-immunology-nephrology). Purpose: align decisions on IVIG, FFP, biopsies, pregnancy, and flares. Mechanism: shared monitoring plans and rapid escalation pathways. KDIGO+1

Drug treatments

Below are commonly used examples in C1q-deficiency management (often mirroring SLE). Always individualize dosing and monitoring.

Hydroxychloroquine. Class: antimalarial/immunomodulator. Typical dose: up to 5 mg/kg/day (actual body weight). Purpose: baseline flare prevention, skin/joint control. Mechanism: blunts Toll-like receptor signaling and antigen presentation. Key risks: retinal toxicity (dose- and duration-related), GI upset. FDAaccessdata+1
Prednisone (incl. delayed-release RAYOS). Class: corticosteroid. Dose/time: short courses for flares; use lowest effective dose; DR forms can target morning cytokine surge. Purpose: rapid inflammation control. Risks: infection, weight gain, glucose/BP rise, bone loss. FDAaccessdata
Prednisolone. Similar steroid used when hepatic conversion matters; warnings include infection masking. FDAaccessdata
Mycophenolate mofetil (CellCept). Class: antimetabolite. Typical: 1–3 g/day in divided doses (per organ involvement; LN often higher). Purpose: steroid-sparing control of renal/skin disease. Risks: teratogenicity, cytopenias, infections. FDAaccessdata
Mycophenolic acid (Myfortic). Enteric-coated mycophenolate; similar effectiveness, GI tolerability advantages for some. Boxed warnings: embryo-fetal toxicity, infections, malignancy. FDAaccessdata
Azathioprine (Imuran). Class: purine antimetabolite. Dose: commonly 1–2.5 mg/kg/day with TPMT/NUDT15 considerations. Purpose: maintenance steroid-sparing in non-renal disease and pregnancy plans. Risks: myelosuppression, malignancy (boxed), hepatotoxicity. FDAaccessdata
Cyclophosphamide. Class: alkylator. Dose: oral 1–5 mg/kg/day or IV pulse protocols for severe organ disease. Purpose: induction in life-threatening disease (e.g., nephritis with crescents, neuro-SLE). Risks: infertility, hemorrhagic cystitis, infections, malignancy; mesna/hydration protocols mitigate urotoxicity. FDAaccessdata+1
Rituximab. Class: anti-CD20 mAb (off-label for SLE; label covers B-cell malignancy/vasculitis). Purpose: refractory B-cell–driven disease. Risks: infusion reactions, HBV reactivation, infections. FDAaccessdata
Belimumab (Benlysta). Class: anti-BLyS mAb; FDA-approved for SLE (IV/SC). Purpose: reduces flares and steroid need in seropositive SLE; helpful in cutaneous/musculoskeletal disease. Risks: infections, hypersensitivity. FDAaccessdata+1
Anifrolumab (Saphnelo). Class: anti-IFN-α receptor mAb; FDA-approved for moderate–severe SLE. Purpose: dampens interferon-driven inflammation. Risks: herpes zoster, respiratory infections; infusion reactions. FDAaccessdata
Methotrexate (low dose, weekly). Class: antimetabolite. Purpose: steroid-sparing for arthritis/skin. Strict weekly dosing; folate supplementation. Risks: liver toxicity, cytopenias; teratogenic. FDAaccessdata
Tacrolimus (calcineurin inhibitor). Purpose: alternative/add-on in refractory cutaneous or renal disease; sometimes used in combo with MMF in LN. Risks: nephrotoxicity, hypertension, tremor. FDAaccessdata
Cyclosporine (modified). Purpose: alternative CNI for resistant cutaneous or renal disease when others fail. Risks: nephrotoxicity, hypertension, gingival hyperplasia. FDAaccessdata
Intravenous immunoglobulin (IVIG). Class: pooled IgG. Purpose: immune modulation for refractory cytopenias/skin disease; occasional reports in C1q deficiency/myopathy contexts. Risks: thrombosis and renal adverse events; boxed warnings emphasize hydration and rate control. U.S. Food and Drug Administration+2U.S. Food and Drug Administration+2
Fresh frozen plasma (FFP) as C1q source (interval infusions). Product: plasma. Purpose: temporary C1q replacement to control flares in select cases and bridge to other care. Caveat: not a long-term, evidence-proven standard; based on case reports/series. Risks: transfusion reactions. OUP Academic+2PMC+2
Short-course high-dose IV methylprednisolone. Class: corticosteroid pulses for life-threatening flares before taper/transition to steroid-sparing agents. (Use follows SLE practice patterns; label similar to prednisone regarding immunosuppression risks.) FDAaccessdata
Antimicrobial prophylaxis when immunosuppressed (case-by-case). Example: PJP prophylaxis during cyclophosphamide/high-dose steroids. Purpose: prevent opportunistic infection. (Practice principle within immunosuppression.) PubMed
Antiplatelet/anticoagulation (selected patients with antiphospholipid features). Purpose: thrombosis prevention if APS features coexist. Mechanism: platelet inhibition/anticoagulation per APS guidance (outside scope of labels here). (SLE framework reference.) PubMed
Topical corticosteroids/calcineurin inhibitors for skin lesions. Purpose: local control of photosensitive rash to spare systemic steroids. (Derm/SLE practice.) PubMed
Adjuncts per organ involvement (e.g., RAAS blockade for proteinuria). Purpose: kidney protection in LN while immunotherapy takes effect. (KDIGO LN.) KDIGO

Important label note: Always consult the current FDA label for dosing and safety; some PDFs above show earlier revisions and explicitly advise checking the latest label. FDAaccessdata

Dietary molecular supplements

Vitamin D3. Typical dose: individualized; many SLE trials used 2,000–4,000 IU/day or weekly 50,000 IU for deficiency. Function: supports bone and may modestly lower disease activity in SLE. Mechanism: immunoregulatory effects on T/B cells and cytokines. Evidence shows heterogeneity but overall trend toward small activity improvements. MDPI+2PMC+2
Omega-3 (EPA/DHA). Dose: commonly 1–4 g/day combined EPA/DHA. Function: may help endothelial function and disease scores in some trials. Mechanism: pro-resolving lipid mediators dampen inflammation. Evidence mixed; small RCTs/meta-analyses suggest modest benefit. Lupus+3PubMed+3ScienceDirect+3
Curcumin. Dose: studied 500–1,500 mg/day standardized curcumin. Function: adjunct to reduce inflammatory markers. Mechanism: NF-κB/NLRP3 and cytokine modulation. Early RCT signals are encouraging but data are limited. PubMed+1
Probiotics (selected strains). Dose: per product/strain. Function: gut–immune axis support; may lower inflammatory cytokines and improve disease indices in preliminary data. Mechanism: enrich T-reg responses, rebalance microbiota. Evidence still early and heterogeneous. PubMed+1
Calcium (if steroid use/osteopenia). Dose: diet first; supplement only to reach daily total goals. Function: bone health. Mechanism: supports mineral homeostasis along with vitamin D. (General practice under steroid exposure.) PubMed
Folic acid (with methotrexate). Dose: typical 1 mg/day (or weekly higher) on non-MTX days. Function: reduces MTX mucosal and hematologic side effects. Mechanism: replenishes folate pools. (MTX standard.) FDAaccessdata
Coenzyme Q10 (experimental). Function: antioxidant support; small autoimmune datasets suggest fatigue benefit, but SLE-specific evidence is limited. Use cautiously with clinician oversight. (Adjunct concept). PubMed
Selenium (if deficient). Function: antioxidant enzyme cofactor; theoretical immune and thyroid benefits; evidence in SLE is limited. Avoid excess. PubMed
Vitamin B12 (if deficient). Function: corrects anemia/neurologic symptoms that can confound fatigue. Mechanism: DNA synthesis, nerve health. Test first; supplement only if low. PubMed
Zinc (short-term if deficient). Function: supports barrier immunity and wound healing. Overuse can cause copper deficiency—monitoring needed. PubMed

Immunity-booster / regenerative / stem-cell” therapies

Allogeneic hematopoietic stem-cell transplantation (HSCT). Not a drug, but the only reported curative approach for C1q deficiency in select cases. Purpose: replace monocyte/macrophage lineage to restore C1q production. Caveat: significant transplant risks; used rarely. PMC
Fresh frozen plasma (FFP) as periodic C1q replacement. Purpose: interim C1q supply to control flares. Evidence: case reports/series; not standardized; risk of transfusion reactions. OUP Academic+1
Mesenchymal stem-cell infusion (investigational in SLE). Purpose: immune reset in refractory autoimmunity. Status: experimental; not approved for C1q deficiency. PubMed
Low-dose IL-2 (investigational). Purpose: expand regulatory T cells; studied in SLE; not approved specifically for C1q deficiency. PubMed
Recombinant C1q or gene therapy (research concept). Purpose: restore the missing protein or gene; currently preclinical/early research. ScienceDirect
Therapeutic plasma exchange (TPE) for severe flares/complications. Purpose: rapidly remove immune complexes/autoantibodies in select organ- or life-threatening scenarios (e.g., DAH, CAPS). Mechanism: extracorporeal removal with replacement fluids (albumin/FFP). Evidence/guidelines: ASFA supports use in specific SLE complications. raeddergisi.org+1

Procedures/surgeries (why they’re done)

Kidney (renal) biopsy. Why: confirm and classify lupus nephritis, which guides drug choice and intensity. KDIGO
Hematopoietic stem-cell transplantation. Why: rare curative intent in confirmed C1q deficiency with severe disease. PMC
Therapeutic plasma exchange (apheresis). Why: rapid control in select critical complications. raeddergisi.org
Central venous access placement. Why: secure long-term IV access for pulses, IVIG, or apheresis when needed. (Procedure necessity per therapy.) U.S. Food and Drug Administration
Skin biopsy. Why: distinguish cutaneous lupus from infection/drug reactions to tailor therapy. PubMed

Prevention tips

Avoid midday sun; use SPF ≥ 30 and UPF clothing daily. American Academy of Dermatology
Keep vaccines current before intense immunosuppression. CDC
Hand hygiene + quick evaluation for fever or cough. CDC
Regular labs/urine checks; act on new swelling or frothy urine. KDIGO
Don’t stop hydroxychloroquine abruptly unless told. FDAaccessdata
Minimize steroid dose and duration. FDAaccessdata
Plan pregnancy; review meds months ahead. PubMed
Heart-healthy lifestyle (no smoking, BP/lipids control). PubMed
Check vitamin D and bone health if on steroids. PubMed
Set up a flare plan and who to call after hours. PubMed

When to see a doctor urgently

Fever ≥38 °C, shaking chills, persistent cough, painful urination, or any rapidly worsening rash. (Infection risk is higher with complement defects or steroids.) CDC
New swelling of legs/face, foamy urine, or sudden rise in blood pressure. (Possible nephritis.) KDIGO
Severe headache, confusion, seizures, chest pain, shortness of breath, or coughing blood. (Possible neuro-SLE, PE, DAH—emergencies.) raeddergisi.org
Pregnancy or planning pregnancy—discuss safe meds and monitoring. PubMed

What to eat and what to avoid

Emphasize: vegetables, fruits, whole grains, legumes, nuts, fish rich in omega-3 (if not contraindicated). (General anti-inflammatory pattern; SLE data mixed but reasonable.) PubMed
Adequate calcium/protein if on steroids, per dietitian. PubMed
Limit salt to help blood pressure and kidneys if nephritis. KDIGO
Stay hydrated (especially around IVIG and in hot weather). U.S. Food and Drug Administration
Avoid high-dose alcohol (liver strain with methotrexate/azathioprine). FDAaccessdata+1
Avoid raw/undercooked meats or unpasteurized foods during high-dose immunosuppression. CDC
Use vitamin D/omega-3 only if indicated by your clinician; don’t megadose. MDPI
Discuss herbals (e.g., St. John’s wort) that interact with CNIs or MMF. FDAaccessdata+1
Caffeine and NSAIDs: avoid excess if kidney disease or blood pressure issues. KDIGO
Food safety on travel—bottled/boiled water, reputable vendors. CDC

Frequently asked questions

Is there a cure? Rarely, HSCT has restored complement activity and resolved disease in reported cases, but it carries serious risks and is not routine. PMC
Can IVIG replace C1q? IVIG modulates immunity but does not supply C1q; some patients still benefit symptomatically. U.S. Food and Drug Administration
Can plasma infusions give me C1q? FFP contains C1q and has been used at intervals to control flares in case reports; effects are temporary. OUP Academic
Do I need lupus medicines if my labs show C1q deficiency? Many do, because the clinical picture often mirrors SLE; choices depend on organs involved. PMC
Why is sun protection so strict? UV frequently triggers cutaneous and systemic flares in lupus-like disease. American Academy of Dermatology
Which vaccines are priorities? Pneumococcal, meningococcal (esp. if on complement-modifying agents), influenza, and COVID-19 per ACIP timing. CDC+2CDC+2
Can I get live vaccines? Avoid during significant immunosuppression; plan timing with your team. CDC
Is hydroxychloroquine safe long-term? Generally yes at proper dosing with annual eye exams; benefits often outweigh risks. FDAaccessdata
What if kidney tests change? Nephrology will consider a biopsy to classify nephritis and guide drugs. KDIGO
Do diet and supplements replace medicines? No—at best they support health; most evidence shows only modest adjunct effects. MDPI+1
Can I breastfeed on my medications? Many SLE meds have breastfeeding guidance; review drug-specific labels and lactation data with your team. FDAaccessdata
Are there new targeted drugs? Anifrolumab and belimumab are approved for SLE and sometimes used when C1q deficiency presents like SLE. FDAaccessdata+1
Is TPE a cure? No—apheresis is a short-term bridge in specific, severe situations. raeddergisi.org
What about pregnancy? Plan ahead; many patients continue hydroxychloroquine and switch to pregnancy-compatible agents. PubMed
Who should coordinate my care? Typically rheumatology with immunology and, if kidneys are involved, nephrology. KDIGO

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