Langerhans cell histiocytosis: Year of the Zebra

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Langerhans cell histiocytosis is a proliferative disorder affecting Langerhans cells, which are immune cells continually patrolling for invading microbes as part of the body’s immune system.
With Langerhans cell histiocytosis, mutated cells infiltrate different body systems, where they can cause damage and form lesions called granulomas.
Symptoms of Langerhans cell histiocytosis vary depending on the body systems affected, ranging from isolated lesions in the skin, bone, or lungs, to systemic disease affecting multiple body systems.
Common skin manifestations include eczematous rashes over the body, brown or purple skin bumps, and bleeding ulcers, especially behind the ears and in the scalp.
Now, if lesions occur in bone, they usually develop in the skull and long bones of the arms or legs, causing localized pain and swelling, as well as increased risk of pathological fractures.
If the skull or facial bones are affected, there is increased risk of central nervous system dysfunction, especially damage to the pituitary gland, a hormone-secreting gland located at the base of the skull.
Pituitary gland dysfunction can result in extreme thirst due to excessive urine production, a condition known as diabetes insipidus.
In severe cases, neurodegeneration can lead to cognitive dysfunction and behavioral issues, as well as ataxia, or difficulty with coordination when walking.
Next, Langerhans cell histiocytosis in the lungs is more common in adults due to its association with smoking and is characterized by shortness of breath, chest pain and cysts that can sometimes rupture and cause the lungs to collapse, leading to spontaneous pneumothorax.
Lastly, in cases of multisystem disease, Langerhans cells may accumulate in the liver or spleen, leading to hepatosplenomegaly; as well as in the bone marrow, where they can crowd healthy blood-forming cells resulting in low blood counts.
Individuals may also experience nonspecific symptoms such as fever, weight loss, and fatigue. Alright, now diagnosis of Langerhans cell histiocytosis may include laboratory blood tests; a complete skeletal survey, which involves a series of X-rays of all the bones in the body; a whole-body CT scan; or MRI of the central nervous system to look for abnormalities in the brain and pituitary gland.
Pulmonary function tests, as well as a bronchoscopy, may be done in cases of lung involvement. Ultimately, diagnosis of Langerhans cell histiocytosis is confirmed through a biopsy of skin, lung, or other affected sites which will show infiltrates of inflammatory cells with abnormal Langerhans cells.
Treatment of Langerhans cell histiocytosis is based on which body systems are affected and whether the disease is isolated or systemic.
Skin lesions in infants may resolve spontaneously during the first year of life without treatment. Older individuals with only bone or skin lesions may be treated with local surgery, radiotherapy, or steroid injections.
On the other hand, if Langerhans cell histiocytosis is found throughout the body or affects high-risk organs, like the brain, liver or spleen, treatment typically involves systemic treatment with chemotherapy; immunotherapy; or targeted molecules, like vemurafenib or dabrafenib, which prevent the growth of mutated Langerhans cells.
Alright, as a quick recap, Langerhans cell histiocytosis is a proliferation of mutated immune cells that have the ability to infiltrate body systems such as the skin, bones, and lungs.
It can range from isolated lesions to multisystem disease. Treatment depends on which organs are affected, including observation, localized treatments, or systemic therapy with chemotherapy,