Pruritus in cholestasis — SCE Dermatology MCQ

Correct answer: D — Cholestatic liver disease

Explanation lettering: D = shown as A · A = shown as B · B = shown as D

B is correct: Cholestatic liver disease. The combination of generalised pruritus without a primary skin eruption, fatigue, dark urine, a markedly raised alkaline phosphatase (610 IU/L), mildly raised bilirubin and positive antimitochondrial antibodies is the classic biochemical and immunological signature of cholestatic liver disease, most likely primary biliary cholangitis (PBC). <cite index="1-1">Primary biliary cholangitis is an inflammatory cholestatic disease that tends to worsen, leading to hepatic cirrhosis and portal hypertension.</cite> Pruritus in cholestasis arises from accumulation of bile acids and other pruritogens (including lysophosphatidic acid and autotaxin activity) in the skin and central nervous system, and characteristically occurs, as here, without a primary rash, only secondary excoriations from scratching. Antimitochondrial antibodies are highly specific for PBC and, combined with a cholestatic (disproportionately raised ALP) liver enzyme pattern, confirm the diagnosis in this clinical context. Why the other options are wrong: A. Primary cutaneous lymphoma: causes pruritus but is associated with a visible primary eruption, patches, plaques or nodules, and does not explain the cholestatic biochemistry or antimitochondrial antibodies. C. Atopic eczema without visible inflammation: eczema by definition produces an inflammatory dermatosis, even if subtle, and does not raise alkaline phosphatase or bilirubin or generate antimitochondrial antibodies. D. Iron overload syndrome: haemochromatosis causes fatigue and skin bronzing rather than isolated itch, and is associated with raised ferritin and transferrin saturation, not a cholestatic liver pattern or antimitochondrial antibodies. E. Chronic urticaria: presents with recurrent wealing (which is itself a primary rash, transient by definition) and normal liver biochemistry, not a cholestatic picture. Key point: Generalised itch with no primary rash plus a cholestatic liver enzyme pattern and positive antimitochondrial antibodies indicates primary biliary cholangitis until proven otherwise.

Reference: Al-Handola R et al, Antimitochondrial Antibody-Negative Primary Biliary Cholangitis: A Retrospective Diagnosis, Cureus 2023;15(3):e36309, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10106268/ (diagnostic criteria for PBC: cholestatic pattern with antimitochondrial antibodies, consistent with UK BSG/UK-PBC guideline approach)