Writing the final diagnosis for CTD-ILD

Write the final diagnosis as a layered statement, not a single label. Name the underlying CTD first, then the ILD pattern, then how it was proven, then severity, behavior and complications.

Template

[CTD with serology/classification] with associated ILD ([HRCT ± histology pattern]), [severity: PFT/extent], [behavior: stable/progressive], with [complications/comorbidities]

Layer	What to state	Examples
1. Underlying CTD	Named disease, antibody profile, criteria met	Rheumatoid arthritis, seropositive (RF+, anti-CCP+), ACR/EULAR 2010 criteria met. Also: SSc (anti-Scl-70), anti-synthetase syndrome (anti-Jo-1), SLE, Sjögren, MCTD (anti-U1 RNP), IIM/MDA5 dermatomyositis
2. ILD pattern	HRCT pattern, plus biopsy pattern if done	NSIP (fibrotic or cellular), UIP, OP, LIP, DAD
3. Basis	Say if it is HRCT-based or biopsy-proven, and that MDD was done	"Diagnosed on HRCT, no biopsy needed" or "consensus after multidisciplinary discussion"
4. Severity	FVC % predicted, DLCO % predicted, extent on HRCT, 6MWT desaturation	"Moderate restriction, FVC 62%, DLCO 45%"
5. Behavior	Stable, or progressive pulmonary fibrosis (PPF)	"Progressive fibrosing phenotype" if criteria are met
6. Complications	Pulmonary hypertension, respiratory failure, esophageal dysmotility/aspiration, infection, drug toxicity	"Type 1 respiratory failure", "group 3 PH"

Example diagnoses

Seropositive rheumatoid arthritis (RF+, anti-CCP+, DAS28 moderate activity) with RA-associated ILD, UIP pattern on HRCT, moderate restrictive defect (FVC 58%, DLCO 40%), progressive fibrosing phenotype.
Limited cutaneous systemic sclerosis (anti-centromere / anti-Scl-70+) with SSc-ILD, fibrotic NSIP pattern on HRCT, mild restriction (FVC 75%), with GERD.
Anti-synthetase syndrome (anti-Jo-1 +) with ILD, NSIP-OP overlap pattern, with inflammatory myositis and mechanic's hands.
Primary Sjögren syndrome (anti-Ro/SSA+) with LIP-pattern ILD.

Points to get right

List the CTD first. The ILD is a manifestation of it, so it comes second. The wording "CTD-ILD" or "RA-ILD" tells the reader the link is established.
Use the correct pattern for the CTD. From the Murray & Nadel table, NSIP is the most common pattern in SSc. UIP is the most common in RA. NSIP is also the commonest overall CTD-ILD pattern (Murray & Nadel's Textbook of Respiratory Medicine, p. 2081-2082).
Write "NSIP pattern" or "UIP pattern", not "NSIP" or "UIP" alone. For CTD-ILD this is the imaging or histologic pattern, not an idiopathic diagnosis.
Do not label it IPF. If the CTD is established, IPF is excluded. If ILD came first and CTD features appeared later, use "IPAF" (interstitial pneumonia with autoimmune features) until criteria for a specific CTD are met.
Rule out mimics and state that you did. These include drug-induced ILD (methotrexate, leflunomide, nitrofurantoin), infection or opportunistic infection under immunosuppression, hypersensitivity pneumonitis, and heart failure. The textbook notes that drug reactions and opportunistic infections can look the same as the underlying disease (Murray & Nadel, p. 2081).
Record who confirmed it. The textbook says a patient with radiographic NSIP should always be fully investigated for an underlying CTD, which may declare itself later. A line like "diagnosis established after rheumatology-pulmonology-radiology MDD" strengthens the presentation.
Present as active problems. Give the main diagnosis first, then secondary diagnoses (for example, steroid-induced hyperglycemia or osteoporosis risk, PJP prophylaxis).

How to say it aloud in the presentation

"Our final diagnosis is seropositive rheumatoid arthritis with RA-associated interstitial lung disease. The HRCT shows a UIP pattern, with basal subpleural honeycombing and traction bronchiectasis. This was confirmed on multidisciplinary discussion, so biopsy was not required. There is moderate restriction with reduced DLCO and exertional desaturation, and she meets criteria for progressive pulmonary fibrosis. There is no clinical evidence of pulmonary hypertension or active infection."

Recent evidence

A 2025 systematic review and meta-analysis of rituximab (PMID 40044124) in CTD-ILD and a 2024 meta-analysis of cardiovascular disease in CTD-ILD (PMID 39222675) are relevant if your presentation covers management or comorbidities. Neither changes how the diagnosis is written.

If you share the case details (CTD, antibodies, HRCT pattern, PFTs), I can write the exact final diagnosis line for you.

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