Refractory Pruriginous Eruption Led to Rectal Cancer Diagnosis
A persistent, treatment-resistant pruriginous pustular eruption turned out to be the first clinical clue to locally advanced rectal cancer in a 72-year-old woman. The presentation is unusual not because colorectal malignancy can produce extraintestinal signs, but because the skin disease was the dominant complaint while gastrointestinal symptoms were absent. In that setting, the case sharpens an old diagnostic principle: unexplained dermatoses in older adults deserve a broader systemic search when standard therapy fails.
The eruption involved the dorsal aspects of the limbs and was symmetric, pustular, crusted, and intensely pruriginous. Several months of dermatologic treatment brought no meaningful relief. Instead of stopping at a skin-only explanation, the evaluation expanded into a non-invasive stool-based work-up. Faecal haemoglobin was detectable by iFOBT, faecal calprotectin measured 51.6 mg/kg with an upper limit of normal of 50 mg/kg, and faecal alpha-1-antitrypsin reached 631 µg/mL, or 2.3 times the upper limit of normal. Stool culture also showed predominance of Escherichia coli.
That sequence matters clinically because the patient never presented with the abdominal pain, bleeding, or bowel habit change that often trigger colorectal investigation. The diagnostic pivot came from the combination of age, refractory skin disease, and an abnormal stool profile rather than from classic bowel symptoms.
Stool Abnormalities Preceded Colonoscopic Confirmation
Colonoscopy identified a rectal adenocarcinoma, and staging classified the lesion as cT3N1M0. In practical terms, the tumour had already extended beyond the rectal wall with nodal involvement, yet remained potentially curable. The case therefore sits at the intersection of dermatology, colorectal oncology, and screening science: a visible skin disorder pointed toward an otherwise occult neoplasm that might have remained hidden longer without further work-up.
The authors propose a gut-skin-tumour axis hypothesis to account for the presentation. No single mechanism can be proven from one patient, but the biological logic is plausible. Chronic malignant disease can alter mucosal integrity, local immune signalling, and systemic inflammatory tone, all of which may affect the skin. Elevated faecal calprotectin suggests intestinal inflammation, while increased faecal alpha-1-antitrypsin points toward protein loss or mucosal barrier dysfunction. In a patient with colorectal neoplasia, those findings may reflect tumor-associated disturbance of the colonic environment rather than isolated incidental abnormalities.
The skin itself improved in parallel with antineoplastic treatment, which strengthens the paraneoplastic interpretation. No separate dermatologic intervention was needed for the eruption to fade. Resolution tracked the cancer-directed treatment course, a pattern that is often seen when a cutaneous manifestation is driven by the underlying tumour burden.
Neoadjuvant Therapy Produced Pathologic Complete Response
Treatment followed standard rectal cancer management. The patient received long-course neoadjuvant chemoradiotherapy with 50 Gy and concurrent capecitabine, then underwent low anterior resection with total mesorectal excision. Surgical pathology showed ypT0N0 with R0 resection, indicating a pathological complete response. Adjuvant capecitabine was then given, and the patient remains in remission at more than 36 months.
This is a striking oncologic outcome for a case that entered care through the skin. The tumour was locally advanced at diagnosis, yet treatment achieved complete eradication on pathology and durable remission. The skin response mirrored the oncologic response, supporting the idea that the eruption was not a separate dermatologic coincidence but part of a tumour-linked systemic picture.
One sentence captures the bedside lesson: a persistent skin eruption can be the first sign of a curable rectal cancer.
FIT as a Triage Tool Beyond Classic Bowel Symptoms
The report argues for careful prospective evaluation of quantitative faecal immunochemical testing in selected patients aged 50 years and older who present with persistent dermatoses of unclear cause. FIT is inexpensive, non-invasive, and already embedded in many pathways for symptomatic lower gastrointestinal assessment. NICE diagnostics guidance DG56 supports its use in adults with suspected lower GI pathology, but extension to extraintestinal presentations remains investigational.
The case does not justify routine FIT for every chronic rash. It does show a realistic niche: older patients with unexplained, refractory inflammatory eruptions, especially when age-appropriate colorectal screening is incomplete or outdated. In that context, a positive FIT may provide a low-barrier route to colonoscopic assessment and shorten the path to diagnosis. The key point is not that every skin eruption signals cancer, but that stubborn dermatoses in older adults can occasionally serve as the first visible clue to occult colorectal disease.
The patient’s stool findings also raise questions about how much diagnostic value lies in combined biomarkers rather than FIT alone. Mild calprotectin elevation, markedly increased alpha-1-antitrypsin, and bacterial predominance on culture created a broader picture of intestinal disturbance. Whether those patterns consistently appear in paraneoplastic skin presentations is unknown. A prospective cohort would need to test diagnostic yield, cost-effectiveness, and stage distribution before any expansion of use can be defended.
Why This Case Changes the Diagnostic Mindset
Dermatologists and primary care clinicians often manage chronic pruritic eruptions without expecting a colorectal diagnosis to emerge. Yet older age, treatment resistance, and the absence of a clear dermatologic explanation should prompt a wider differential. The value of this case lies in the path from symptom to diagnosis: a skin eruption with no gastrointestinal complaints, a non-invasive stool assessment, a colonoscopic finding of rectal cancer, and complete oncologic response after multimodal therapy.
What remains unproven is the prevalence of this presentation and the degree to which FIT would identify meaningful colorectal lesions in similar patients. A single case can suggest a diagnostic bridge, not build one. Formal validation will need prospective studies that measure how often persistent pruriginous or pustular eruptions uncover colorectal neoplasia, whether FIT adds useful triage value, and how many patients would avoid delayed diagnosis by using a broader referral threshold.