Acquired ichthyosis
Acquired ichthyosis vulgaris; "ichthyosis acquisita"; the adult-onset symmetrical fish-scale dryness — distinct from congenital / hereditary ichthyoses
Acquired ichthyosis is the adult-onset development of symmetrical, generalised, fish-scale-like dry skin in a patient without family history of ichthyosis or congenital onset. Clinically and histologically it resembles ichthyosis vulgaris (the commonest hereditary ichthyosis) but is acquired in adulthood, frequently rapidly, and almost always reflects an underlying systemic process. The skin-oncology importance is the strong association with haematological malignancy — most commonly Hodgkin lymphoma (~50–60% of paraneoplastic cases (older series quoted ~70%)) and various non-Hodgkin lymphomas, mycosis fungoides, multiple myeloma, leukaemia and Kaposi sarcoma. Other causes — HIV infection, malabsorption (coeliac, IBD, post-bariatric surgery), endocrine disorders (hypothyroidism), nutritional deficiency (essential fatty acid, zinc, vitamin A), chronic renal failure, drugs (statins, kava, triparanol, nicotinic acid, BRAF inhibitors, anti-PD-1) — must be excluded. New-onset ichthyosis in an adult mandates lymphoma workup as the priority.
Clinical features
- Symmetrical, generalised, fine to coarse polygonal dry "fish-scale" scaling.
- Distribution — extensor surfaces of arms and legs (particularly shins) most prominent; trunk; spares face, palms, soles and flexures (similar to inherited ichthyosis vulgaris).
- Onset — typically rapid over weeks to months, in an adult without family history of ichthyosis.
- Often pruritic.
- Hyperlinearity of palms (variable).
- Differential — inherited ichthyosis vulgaris (childhood onset, family history), inherited X-linked ichthyosis (men, with corneal opacities), severe atopic dermatitis with xerosis, acquired non-paraneoplastic ichthyosis (HIV, drugs, endocrine, nutritional, renal — see below).
Underlying causes
- Haematological malignancy (the principal paraneoplastic associations):
- Hodgkin lymphoma — the classical association; modern reviews usually place it around ~50–60% of paraneoplastic cases, with older series quoting ~70%.
- Non-Hodgkin lymphoma.
- Cutaneous T-cell lymphoma (mycosis fungoides) — see CTCL.
- Multiple myeloma, Waldenström macroglobulinaemia.
- Acute / chronic leukaemia.
- Kaposi sarcoma — a vascular (HHV-8) neoplasm rather than a haematological malignancy; reported particularly in the HIV context.
- Solid tumours — much less common; lung, breast, ovarian, GI, cervical carcinoma described.
- Non-malignant causes (must exclude before diagnosing as paraneoplastic):
- HIV infection.
- Hypothyroidism (and other endocrinopathies).
- Malabsorption — coeliac disease, IBD, post-bariatric surgery.
- Nutritional deficiency — essential fatty acid, zinc, vitamin A, vitamin D.
- Chronic renal failure.
- Drug-induced — statins, kava, nicotinic acid, allopurinol, hydroxyurea, BRAF inhibitors, anti-PD-1, MEK inhibitors, EGFR inhibitors, isotretinoin.
- Sarcoidosis, leprosy.
- Connective tissue disease — particularly DLE, scleroderma.
Workup — prioritise lymphoma
- History — family history (exclude inherited ichthyosis), drugs, weight loss, fevers, night sweats, lymphadenopathy, GI symptoms, HIV risk factors.
- Examination — lymph nodes, hepatosplenomegaly, full skin including mucosa.
- FBC with peripheral blood film, ESR / CRP, LDH, U&E, LFT, calcium, immunoglobulins, serum protein electrophoresis.
- HIV serology.
- Thyroid function tests.
- Coeliac serology, vitamin and mineral panel.
- CT chest, abdomen, pelvis ± PET-CT — first-line; particularly to identify Hodgkin lymphoma.
- Lymph-node biopsy of any palpable / imaging-detected lymphadenopathy.
- Bone marrow biopsy if cytopenias / paraprotein.
- Skin biopsy — typically non-specific (resembling ichthyosis vulgaris with mild orthokeratosis and reduced / absent granular layer); does not contribute to diagnosis of underlying cause.
- Refer to haematology MDT if any abnormality.
Management
- Treat the underlying cause — acquired ichthyosis typically resolves with successful treatment of underlying malignancy or correction of metabolic / nutritional cause.
- Symptomatic skin care:
- Daily liberal emollients (urea 10–40%, lactic acid, ceramide-containing).
- Bath oils.
- Topical retinoids (if tolerated).
- Oral retinoids (acitretin, alitretinoin) for severe disease.
- Phototherapy — limited evidence.
- Multidisciplinary care — dermatology, haematology, endocrinology, gastroenterology as indicated.
- If initial workup is negative — repeat at 6 and 12 months; acquired ichthyosis may precede cancer diagnosis by months.
References
- Patel N et al. Acquired ichthyosis — review. J Am Acad Dermatol; 2006.
- Polat M et al. Acquired ichthyosis associated with malignancy — review. Eur J Dermatol; 2009.
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