Derm Cases · Dermatology / Allergy / Haematology interface
OSCE — Darier-positive pigmented macules: cutaneous mastocytosis and anaphylaxis planning
An 8-minute OSCE station on recognition of urticaria pigmentosa with Darier's sign, distinction of cutaneous vs systemic mastocytosis, tryptase/KIT work-up triggers, mediator-directed therapy, and anaphylaxis preparedness including IM adrenaline.
On this page
Study tools
Target exams
NEET-PGINICETUSMLEPLABMRCP
Prompt
An 8-minute OSCE station on recognition of urticaria pigmentosa with Darier's sign, distinction of cutaneous vs systemic mastocytosis, tryptase/KIT work-up triggers, mediator-directed therapy, and anaphylaxis preparedness including IM adrenaline.
Brief (to candidate)
A 4-year-old has multiple reddish-brown macules and papules on the trunk that wheal when rubbed. Parents report episodic flushing after insect stings. Growth is normal; no organomegaly is found. You have 8 minutes to diagnose, decide who needs systemic work-up, and plan mediator control plus anaphylaxis safety.
Candidate instructions
- Recognise urticaria pigmentosa / maculopapular cutaneous mastocytosis and elicit Darier's sign.
- Distinguish purely cutaneous disease (common in children) from features suggesting systemic mastocytosis.
- State when to measure serum tryptase and pursue marrow/KIT evaluation.
- Outline H1 ± H2 antihistamines, trigger avoidance, and anaphylaxis kit counselling.
- Give the correct IM adrenaline dose for anaphylaxis.
Examiner checklist (mark each domain / 10)
| Domain | Key actions expected |
|---|---|
| Recognition | Reddish-brown macules/papules; positive Darier's sign (wheal/flare on stroking) = cutaneous mastocytosis / UP phenotype[1] |
| Classification | Paediatric cutaneous mastocytosis often limited to skin and may regress; adult-onset lesions more often linked to systemic mastocytosis[1][2] |
| When to escalate | Persistent tryptase >20 ng/mL, recurrent anaphylaxis, cytopenias, organomegaly, unexplained bone pain → systemic algorithm (ECNM/WHO pathway, KIT D816V, marrow)[5][2] |
| Mediator therapy | Non-sedating H1 antihistamine regularly; add H2 for GI symptoms; mast-cell stabilisers/ketotifen where available; avoid known degranulators (opioids, some anaesthetics, alcohol, temperature extremes)[1] |
| Anaphylaxis plan | Prescribe two adrenaline auto-injectors; teach IM technique; insect-sting avoidance; consider venom immunotherapy if venom-allergic; avoid beta-blockers when possible[9] |
| Acute dose | Adult IM adrenaline 0.5 mg (1:1000) anterolateral thigh; child 0.01 mg/kg (max 0.3 mg); may repeat every 5 minutes if no response[9] |
| Communication | Explain chronic mediator risk, when to seek emergency care, and that not every childhood UP needs marrow biopsy |
Model key actions
- Diagnose maculopapular cutaneous mastocytosis with Darier's sign.[1]
- Reserve systemic work-up for red-flag / tryptase-elevated phenotypes using ECNM-style algorithms.[5]
- Start antihistamine-based control and equip the family for anaphylaxis with IM adrenaline.[9]
Common errors
- Missing Darier's sign and treating as simple urticaria or freckling.
- Ordering bone marrow biopsy for every child with limited UP and no systemic features.
- Discussing antihistamines without an adrenaline auto-injector plan in anaphylaxis-prone patients.
- Using IV antihistamines/steroids as a substitute for IM adrenaline in anaphylaxis.
- Forgetting insect-sting and peri-anaesthetic degranulation risks.
References4ShowHide
- [1]Di Raimondo C, Del Duca E, Silvaggio D, et al. Cutaneous mastocytosis: A dermatological perspective. Australasian Journal of Dermatology, 2021.PMID 33040350
- [2]Li JY, Ryder CB, Zhang H, et al. Review and Updates on Systemic Mastocytosis and Related Entities. Cancers (Basel), 2023.PMID 38067330
- [5]Valent P, Escribano L, Broesby-Olsen S, et al. Proposed diagnostic algorithm for patients with suspected mastocytosis: a proposal of the European Competence Network on Mastocytosis (ECNM). Allergy, 2014.PMID 24836395
- [9]Gülen T, Akin C Anaphylaxis and Mast Cell Disorders. Immunology and Allergy Clinics of North America, 2022.PMID 34823750