Histiocytosis X/Langerhans Cell Histiocytoses
Langerhans cell histiocytoses (Class I histiocytosis) are a group of disorders most common in childhood due to the accumulation or proliferation of a clonal population of cells bearing the phenotype of a Langerhans cell that has been arrested at an early stage of activation and is functionally deficient. This disorder is classified as single-system disease, multisystem disease, or multisystem disease with organ dysfunction. The skin is one of the most frequently affected organs in patients with both localized (skin only) and multisystem disease. The course in any patient varies from benign (usually associated with localized disease or multisystem disease without organ dysfunction, to severe and fatal, with internal organ dysfunction. Dysfunction of lungs, liver, and/or bone marrow are very poor prognostic signs. Skin-limited cases and sometimes systemic disease may spontaneously involute without therapy. Disease may recur after involution, even years later; therefore long-term follow-up is essential. Langerhans cell histiocytoses syndromes are uncommon, and most patients should be evaluated and usually managed at tertiary referral centers.
Patients may be observed without therapy. Autoinvolution often occurs.
- For a solitary lesion, excision may be curative.
- Topical nitrogen mustard 20 mg/100 ml tap water applied once daily until the lesions clear (several weeks). Weekly or biweekly maintenance therapy may be required.
- For patients who have failed treatment with nitrogen mustard, systemic PUVA twice weekly is recommended. Maintenance may be required.
- Prednisone alone, up to 2 mg/kg in children, may be used for extensive, unresponsive cutaneous disease.
- Trimethoprim/sulphamethoxazole 12-15 mg/kg/day for 1-3 months may be effective in children.
- Thalidomide 100 mg/day for 1 month, then 50 mg/day for 1-2 months.
- Isotretinoin 1.5 mg/kg/day for 6 or more months may induce a remission.
- For severe skin-limited disease, single agent chemotherapy may be considered. Effective agents have included methotrexate, vinblastine, 6-mercaptopurine, and etoposide. Alpha interferon in doses of up to 6 million units daily can be used in refractory disease. While cyclosporine in high doses 12 mg/kg/day leads to resolution of skin disease, relapses frequently occur.
- Congenital self-healing reticulohistiocytosis is a benign Langerhans cell histiocytosis. This diagnosis should be entertained in neonates with lesions over 1 cm and skin involvement only. As the name implies, autoinvolution occurs universally by 3 months.
- Severe combined immunodeficiency syndrome and graft vs. host disease may closely mimic Langerhans cell histiocytosis. In Langerhans cell histiocytosis, most patients are immunologically normal prior to therapy when evaluated by standard tests.
- Morbidity and mortality may be reduced by appropriate nonaggressive therapy (often no therapy). Do not produce unnecessary permanent sequelae from overaggressive local or systemic treatments.
- Long-term follow-up is essential to detect disease relapse and to monitor for long-term complications (cosmetic, orthopaedic, hearing impairment, loss of permanent teeth, pulmonary fibrosis, cor pulmonale, portal hypertension, cirrhosis, endocrinologic disorders from pituitary involvement, and second malignancies).