Morphoea
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Direct answer
An ivory-hard plaque with a violaceous "lilac ring" edge, and no Raynaud phenomenon — that combination is morphoea (localised scleroderma), a fibrosing disorder of skin and subcutaneous tissue producing discreet, well-demarcated plaques without internal organ involvement. It is distinct from systemic sclerosis: no nail-fold capillary dropout, no pulmonary, renal or gastrointestinal disease, and antinuclear antibodies, when present, do not predict visceral involvement. Subtypes are plaque (most common, trunk), generalised, bullous, deep (subcutaneous), and linear — the childhood form that follows a limb or, on the face and scalp, the frontoparietal "en coup de sabre" line, sometimes with ipsilateral hemifacial atrophy (Parry-Romberg syndrome). Active progressive disease is treated with methotrexate 15 mg weekly plus systemic corticosteroids; limited plaque disease responds to very potent topical steroids and phototherapy.
What you must remember
- Lilac ring: the inflammatory, violaceous advancing edge around an ivory sclerotic centre — its presence means active, treatable disease; a uniformly hard white plaque is burnt out.
- Subtype map: plaque morphoea (trunk and limbs, adults), generalised (four or more confluent plaques), linear (a limb in a child, causing growth arrest and contracture if it crosses a joint), en coup de sabre (frontoparietal scalp and face, like a sabre cut), deep/morphea profunda (fascia involved).
- The systemic sclerosis exclusions: normal nail-fold capillaroscopy, absence of Raynaud phenomenon and of internal organ disease — quoting these three is how you defend the diagnosis.
- Antibodies: ANA positive in a substantial minority; anti-histone antibodies associate with linear and juvenile disease; anti-centromere and anti-Scl-70 argue for systemic sclerosis, not morphoea.
- First-line for active progressive disease: methotrexate 15 mg weekly (oral or subcutaneous) with folic acid, plus prednisolone 0.5-1 mg/kg/day tapered over months — the paediatric rheumatology convention.
- Limited plaque disease: very potent topical corticosteroid (clobetasol propionate 0.05%) with or without calcipotriol, or UVA1 phototherapy.
- Linear disease in children: start systemic therapy early and add physiotherapy — the danger is growth arrest of the limb and fixed joint contractures, not the cosmetic plaque.
- Beware mimics: eosinophilic fasciitis (peripheral eosinophilia, groove sign, strenuous-exercise history), scleroderma of chronic graft-versus-host disease, and post-radiotherapy fibrosis.
Deciding activity, then depth, then drug
A 9-year-old girl is brought for a "scar-like" streak down one leg that has crossed the knee over eight months; the knee is already losing extension. The streak is indurated with a faint lilac-violet edge, and the limb is measurably thinner than the other. This is linear morphea with functional risk, and it is the scenario that must not be managed with cream alone. After baseline blood counts and liver function, she is started on prednisolone 1 mg/kg/day and methotrexate 15 mg weekly with folic acid 5 mg weekly on the methotrexate-free day — the standard paediatric regimen — plus intensive physiotherapy and serial limb-length and joint-range measurement. The iliac ring fading is your pharmacodynamic marker of response; the hard white residue softens only partially.
Contrast a 44-year-old woman with two coin-sized, long-static ivory plaques on the abdomen, no edge, no symptoms. Activity is absent, so systemic immunosuppression is unjustified; topical clobetasol under occlusion and monitoring suffice. The practical teaching is that morphoea management is dictated by two assessments — is it active (lilac edge, erythema, warmth, extension) and is it deep/linear (functional consequence) — and both are clinical judgements made before any prescription.
How the examiner frames it
Two questions dominate. First, "differentiate morphoea from systemic sclerosis" — the expected answer pairs the skin-only fibrosis of morphoea with absent Raynaud, normal nail-fold capillaries and no internal disease. Second, the en coup de sabre image with the eponym Parry-Romberg when hemifacial atrophy accompanies it. A less appreciated trap is the "burnt-out plaque" stem: hard white plaque without lilac ring means no active inflammation, so the correct answer is reassurance and topical care, not methotrexate. Viva examiners also like the drug regimen convention — methotrexate 15 mg weekly with folic acid cover and steroid bridging — including the practical detail that folic acid is given on a day other than methotrexate day in most Indian protocols.
Frequently asked questions
What distinguishes morphoea from systemic sclerosis?
Morphoea is localised fibrosis of skin and subcutis without Raynaud phenomenon, nail-fold capillary abnormalities or internal organ involvement, which systemic sclerosis shows.
Which morphoea subtype occurs on the frontoparietal scalp?
Linear morphoea of the face — en coup de sabre — a depressed sclerotic band on the scalp and forehead, sometimes with Parry-Romberg hemifacial atrophy.
What does a lilac ring signify?
A violaceous inflammatory border around the sclerotic plaque indicates active, progressing disease that still responds to anti-inflammatory and immunosuppressive therapy.
What is the standard treatment for progressive linear morphoea in a child?
Methotrexate 15 mg weekly with folic acid plus systemic corticosteroids (prednisolone 0.5-1 mg/kg/day tapered), combined with physiotherapy to prevent contracture.
Is antinuclear antibody testing useful in morphoea?
ANA is positive in a minority and does not predict internal disease; anti-histone antibodies associate with linear/juvenile disease, while Scl-70 or centromere antibodies suggest systemic sclerosis.