Langerhans cell histiocytosis (cutaneous)
LCH; "histiocytosis X" (older umbrella term — now obsolete); Letterer-Siwe disease (older — disseminated infantile multisystem variant); Hand-Schüller-Christian disease (older — multifocal triad); eosinophilic granuloma (older — single-system bone variant); Hashimoto-Pritzker disease (congenital self-healing variant)
Langerhans cell histiocytosis is a clonal histiocytic / dendritic-cell neoplasm within the modern histiocytic and dendritic-cell neoplasm framework. It was reclassified away from a purely reactive disorder after recurrent activating MAPK-pathway mutations were recognised — most importantly BRAF V600E in ~50% and MAP2K1 (MEK1) mutations in many of the remainder. The disease spans an enormous spectrum of severity: from single-system "self-healing" cutaneous disease in infants (Hashimoto-Pritzker), through chronic multifocal disease (Hand-Schüller-Christian: lytic skull lesions + diabetes insipidus + exophthalmos), to acute disseminated multisystem disease in infants with high mortality (Letterer-Siwe). Cutaneous involvement is one of the commonest presentations, ranging from "seborrhoeic-dermatitis-like" infantile scalp / inguinal eruption to discrete papules, nodules, ulcers and pustular lesions in any age group. The dermatologist may be the first to recognise the disease and trigger life-saving systemic workup. Targeted MAPK pathway inhibitors (vemurafenib, dabrafenib, trametinib) have transformed the prognosis of refractory disease.
Pathobiology & reclassification
- Clonal proliferation of CD1a+ / CD207 (langerin)+ dendritic cells.
- Classified in the modern haematolymphoid framework as a histiocytic / dendritic-cell neoplasm; the key practical shift is that LCH is a clonal MAPK-driven neoplasm rather than a reactive disorder.
- Driven by recurrent activating mutations of the MAPK pathway:
- BRAF V600E in ~50%.
- MAP2K1 (MEK1) mutations in ~25%.
- Other activating MAPK mutations (ARAF, NRAS) in smaller proportion.
- Mutation testing (BRAF V600E IHC + sequencing of biopsy / circulating tumour DNA) is now standard for prognostication and treatment selection.
Clinical spectrum
- Cutaneous involvement — common presenting feature; patterns include:
- Infantile scalp / inguinal eruption — yellow-brown, scaly, "seborrhoeic-dermatitis-like" papules and erosions; key clue is petechiae and erosions within the eruption.
- Discrete papules, nodules, vesicles, pustules.
- Hyperpigmented or hypopigmented patches.
- Erosive / ulcerative oral, genital and intertriginous lesions.
- Mucosal involvement (gingival, oral).
- Hashimoto-Pritzker (congenital self-healing reticulohistiocytosis) — congenital papulonodular eruption that regresses spontaneously over weeks to months without other organ involvement; favourable course.
- Other organ involvement:
- Bone — lytic lesions (skull, long bones, vertebrae); commonest single-system manifestation.
- Pituitary / hypothalamus — diabetes insipidus (most common endocrinopathy); growth hormone deficiency.
- Liver, spleen, bone marrow — "risk organ" involvement; substantially worse prognosis.
- Lung — cystic lung disease (adult smokers).
- CNS — neurodegenerative LCH (cerebellar / brainstem white-matter changes).
- Median age of onset 2 years; can present at any age including adults.
Histology & immunophenotype
- Dense dermal infiltrate of large pale histiocytes with characteristic "kidney-shaped" / reniform / coffee-bean-shaped nuclei.
- Eosinophils, lymphocytes, neutrophils admixed.
- Epidermotropism with single Langerhans cells in the epidermis.
- Diagnostic immunophenotype:
- CD1a+, CD207 (langerin)+, S100+ — diagnostic triad.
- Birbeck granules on electron microscopy (now superseded by langerin IHC, which highlights the same structures).
- BRAF V600E IHC — positive in ~50%; informs targeted therapy.
Staging & risk stratification
- Comprehensive multidisciplinary workup essential at presentation:
- Full clinical and skin examination.
- FBC, U&E, LFT, coagulation, ESR.
- Urine osmolality and serum osmolality (diabetes insipidus screen).
- Skeletal survey or whole-body MRI / PET-CT.
- CT chest / lung function tests in adults.
- Bone marrow biopsy if cytopenias.
- Pituitary MRI if endocrine symptoms.
- BRAF V600E mutation testing on biopsy ± circulating tumour DNA.
- Risk stratification — single-system vs multisystem; "risk organ" involvement (liver, spleen, bone marrow) defines high-risk multisystem disease.
- Refer to a Histiocyte Society / specialist haematology service (UK paediatric histiocytosis: Great Ormond Street; adult: Royal Marsden, UCLH).
Management
- Risk-adapted, MDT-led:
- Single-system cutaneous LCH — observation, topical corticosteroid, topical nitrogen mustard, narrowband UVB, low-dose oral methotrexate, hydroxychloroquine.
- Single-system bone LCH — curettage, intralesional corticosteroid, low-dose radiotherapy.
- Multisystem LCH (low-risk and high-risk) — vinblastine + prednisolone (LCH-IV / similar protocols); cladribine and cytarabine for relapsed / refractory disease.
- Refractory or risk-organ-involved disease — vemurafenib / dabrafenib (BRAF V600E mutants) or trametinib (MAP2K1 / BRAF wild-type) — high response rate, but used off-label and specialist-led in the UK (not NICE-approved for LCH), with frequent relapse on discontinuation.
- Supportive care — DDAVP for diabetes insipidus, growth hormone replacement, smoking cessation (adult lung LCH).
- Long-term surveillance — late effects (endocrine, neurodegenerative, second malignancy) common.
References
- Allen CE et al. Langerhans-cell histiocytosis. N Engl J Med; 2018.
- Diamond EL et al. Vemurafenib for BRAF V600-mutant Erdheim-Chester disease and Langerhans cell histiocytosis. JAMA Oncol; 2018.
Spot a correction?
If any clinical statement, citation or link on this page needs updating, please email admin@skinoncology.net with the page name, the proposed correction and the supporting source.