Complement Deficiencies AND Recurrent Infections

The answer first

Complement Deficiencies AND Recurrent Infections is managed with an answer-first physician approach: recognise the pattern, exclude dangerous differentials, choose investigations that change action, and deliver a sequenced management plan that accounts for multimorbidity. [1] [2]

The FRACP candidate must be able to open a long-case presentation, defend thresholds, and answer DWE vignettes without hedging. Lead with the decision, then the evidence and the trap. [1]

Clinical spectrum and red flags

Presentations range from incidental or outpatient findings to emergency decompensation. Always ask what would make this urgent today — airway, perfusion, neurological threat, metabolic crisis, infection, or bleeding. [1] [2]

Red flags force same-day action rather than elective pathways. Document them explicitly in the plan. [1]

Classification that changes management

Classify by acuity, mechanism, severity and care setting. A useful classification changes investigation choice, initial therapy, disposition or specialist referral — otherwise it is taxonomy without purpose. [1] [2]

Pathophysiology linked to bedside decisions

Mechanism matters when it predicts treatment response, complications or monitoring. Teach pathophysiology as a bridge to action, not as isolated basic science. [1] [2] [3]

Differentials and discrimination

Build a short differential that includes the common, the dangerous and the commonly missed. For each alternative, name one history clue, one examination clue and one investigation that discriminates. [1] [2]

Investigations

Order tests that change management. State what is required now, what can wait, and what is low-value or harmful. Interpret results in clinical context rather than in isolation. [1] [2]

Management — immediate then definitive

1. Stabilise threats to life and organ function. [1]
2. Start disease-specific therapy once the working diagnosis is secure enough to act. [1] [2]
3. Address complications, drug interactions and monitoring. [1] [2]
4. Plan disposition, follow-up intensity and patient education with safety-net advice. [1]

Complications and prognosis

Anticipate early and late complications. Prognosis depends on severity at presentation, speed of effective therapy, comorbidity and adherence to secondary prevention or disease-modifying treatment. [1] [2]

Special populations and multimorbidity

Adjust for pregnancy potential, frailty, CKD, liver disease, immunosuppression and polypharmacy. In older adults, goals-of-care and treatment burden can change the preferred plan even when disease-directed options remain available. [1] [2]

DCE long-case angles

Open with a one-sentence synthesis, then a prioritised problem list, then an integrated plan covering investigations, treatment, prevention and communication. Link Complement Deficiencies AND Recurrent Infections to cardiovascular risk, infection risk, medications and social context where relevant. [1] [2]

DCE short-case angles

Be prepared to demonstrate or discuss focused examination findings, interpret a key investigation, and counsel on risks, benefits and follow-up in plain language. [1]

Exam traps

1. Delaying urgent care because the presentation looks "stable enough". [1]
2. Treating a syndrome label without confirming mechanism. [1] [2]
3. Forgetting drug interactions and organ-function dosing. [1] [2]
4. Omitting safety-net advice and follow-up ownership. [1]
5. Quoting thresholds without knowing the source trial or guideline. [1] [2] [3]

References

1. [1]Mottaghipisheh H, Jahromi AM, Mirzaei F, Meri S, et al. Homozygous C1qA Deficiency Presenting as Early-Onset Systemic Lupus Erythematosus: A Case Report With a Literature Review Case Reports Immunol, 2026.PMID 42147803
2. [2]Consolini R, Maestrini G, Abu-Rumeileh S, Costagliola G The Intertwining Between Arthritis and Inborn Errors of Immunity J Clin Med, 2026.PMID 42123030
3. [3]Boccon-Gibod I, Fain O, Gobert D, Debord S, et al. French protocol for the diagnosis and management of hereditary angioedema Rev Med Interne, 2025.PMID 41168057
4. [4]Schejbel L, Fadnes D, Permin H, Lappegård KT, et al. Primary complement C5 deficiencies - molecular characterization and clinical review of two families Immunobiology, 2013.PMID 23743184
5. [5]Xi Y, Yao T, Zhang C, Zhuang T Effectiveness of safety care and clinical nursing pathway in patients undergoing cardiovascular intervention: a randomized controlled trial Perioper Med (Lond), 2026.PMID 42469924
6. [6]Marks FJ, Walters SJ, Sutton L, Jacques RM What statistical methods are more appropriate for predicting recruitment at the design stage of a randomised controlled trial? Trials, 2026.PMID 42469922
7. [7]Hajiaqaei M, Mohammadi A Transcranial random noise stimulation (tRNS) over the left dorsolateral prefrontal cortex ameliorates emotion dysregulation and executive function: a single-blind, randomized, sham-controlled clinical trial BMC Psychol, 2026.PMID 42469906
8. [8]Donadoni M, La Cava L, Bizzi E, Popescu Janu V, et al. Hereditary Angioedema Prophylaxis Therapy: Berotralstat and Lanadelumab Safety Profile Medicina (Kaunas), 2025.PMID 41303734
9. [9]Rajabi E, Kheirabadi MC, Olyaei NA, Molitor A, et al. Complete Complement Factor I (CFI) deficiency: a systematic review of forty-nine patients including three novel cases BMC Immunol, 2025.PMID 40713518
10. [10]Shields AM, Pagnamenta AT, Pollard AJ, OxClinWGS, et al. Classical and Non-classical Presentations of Complement Factor I Deficiency: Two Contrasting Cases Diagnosed via Genetic and Genomic Methods Front Immunol, 2019.PMID 31231365