Langerhans cell histiocytosis (LCH) is a rare multisystem disorder. It is a reactive increase in the number of Langerhans cells which act as antigen-presenting cells in the epidermis. It most commonly affects children from 1 – 3 years of age. It is slightly more common in males. LCH affects 2–5 children per million per year with an estimated prevalence of 1:50 000 children under 15 years of age. LCH has been associated with Epstein-Barr virus in some cases.

Classification:

This condition can appear in a variety of forms, and several of the well-known patterns have been given unique names. These include:

Letterer-Siwe disease: Usually in children less than two years of age, involves many organs including bones, lungs, and the liver. Skin affection can appear in the scalp, trunk, and groin manifesting as pinkish papules or blisters that me crust. It can mimic cradle cap which is seen in seborrheic dermatitis.
Hand-Schuller-Christian disease: Usually in children from 2 – 6 years of age, the skin and bone especially the skull. Manifest as a pinkish-crusted papule, with ulcers in the mouth or genitals, and rarely eye protrusion. It often results in diabetes insipidus.
Eosinophilic granuloma: Usually in school-age children, less commonly affects the skin, usually present as a single bone lesion.
Congenital self-healing reticulohistiocytosis: Usually present at birth as a widespread reddish lump on the skin which breaks and results in a crust that fades with time with no intervention. It is limited to the skin.

A newer classification is also used where it is based on the number of involved organs in a single system (SS-LCH) and multisystem (MS-LCH) disease.

Diagnosis:

The diagnosis is suspected with the described rash and X-ray scans of internal organs. LCH is confirmed by skin biopsy. When histiocytosis is diagnosed in one organ, other organs should be checked to detect if it was affected.

Management:

If the disease was limited to the skin the following therapies could be utilized: topical corticosteroids, topical antibiotics, photochemotherapy, and thalidomide. In cases of pain lesions, the following medications can be used non-steroidal anti-inflammatory drugs, steroids injection, and radiotherapy.

In cases of multisystem involvement, starting with oral corticosteroids, then chemotherapy is warranted. The choice of treatment depends on several factors including age, and organ involvement. BRAF-V600 inhibitors may be beneficial such as vemurafenib and dabrafenib.

Prognosis:

Many people may have little or no symptoms of a minor disease that is limited to one organ. There is an excellent prognosis for these individuals. In cases of several organ involvement, it could be fatal. In those younger than two years, a disease involving multiple organs, and vital organs such as the liver are the predictor of poor outcomes in LCH. The mortality rate for children under two years old who have multiple organ involvement from LCH is between 40-50%.

Written by:

Mohammed Alahmadi, Medical Student.

Revised by:

Maee Barakeh, Medical Student.

References:

DermNet

Dermatology by Bolognia

Practical Guide to Dermatology, The Henry Ford Manual

Primary Care Dermatology Society