Lichen myxoedematosus (scleromyxoedema)

Definition

Lichen myxoedematosus (papular mucinosis) is a rare idiopathic cutaneous mucinosis with deposition of mucin in the dermis. A generalised form, scleromyxoedema, which can involve internal organs and may be fatal, is distinguished from localised forms that do not run a disabling course.

Classification

• Scleromyxoedema (generalised): generalised papular and sclerodermoid eruption, mucin with fibroblast proliferation and fibrosis, monoclonal gammopathy, no thyroid disease.
• Localised forms (without gammopathy or thyroid disease): discrete papular, acral persistent (extensor hands and wrists), self-healing, infantile, nodular.
• Atypical forms that do not clearly meet either set of criteria.

Aetiopathogenesis

The cause is unknown. Scleromyxoedema is nearly always associated with a monoclonal gammopathy, usually IgG-lambda, whose role is unclear. It mainly affects adults between 30 and 50 years of age, men and women equally.

Clinical features

• Scleromyxoedema: closely set, 2–3 mm, skin-coloured, waxy papules, often in lines, on the face, trunk and limbs; scalp and mucous membranes spared. Later deep furrowing of the brow, sclerodactyly and reduced mouth opening – as in systemic sclerosis, but without telangiectasia or calcinosis.
• Possible involvement of the oesophagus, muscles, lungs, joints, kidneys and nervous system, among others.
• Localised forms: a few firm, waxy papules without skin hardening.

Histology

Mucin throughout the dermis with fibroblast proliferation and increased collagen, more marked in scleromyxoedema. It stains with colloidal iron and Alcian blue (pH 2.5); PAS is negative.

Diagnosis

• Skin biopsy is the key investigation.
• Serum and urine protein electrophoresis (paraprotein), thyroid function, antinuclear antibodies; if a paraprotein is present, possibly a bone marrow biopsy.

Differential diagnoses

• Cutaneous amyloidoses
• Granuloma annulare
• Mycosis fungoides
• Lipoid proteinosis (Urbach–Wiethe disease)
• Scleroedema adultorum of Buschke (scleredema)
• Morphea
• Limited systemic sclerosis (CREST syndrome)
• Dermatomyositis

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References (selection)

1. DermNet: Lichen myxoedematosus
2. DermNet: Papular mucinosis pathology
3. Updated classification of papular mucinosis, lichen myxedematosus, and scleromyxedema
4. New insights on scleromyxedema

Cross-references