At the week follow-up, the lesions were unchanged and the swelling on the left lateral eyebrow was worsening. A biopsy of the yellow lesion on the back and one of the scaly papules on the abdomen was performed. A fungal and bacterial cultures were also ordered.
He was referred to ophthalmology for evaluation of the eyelid swelling and an ultrasound was requested.
The skin biopsy showed a clonal proliferation of reniform histiocytes with eosinophils within the dermis. The cells were positive for S100, CD207 (langerin), and CD1a and negative for pancytokeratin and Melan-A, supportive of the diagnosis of Langerhans cell histiocytosis (LCH).
Diagnosis
The patient was admitted to the hospital, where a skeletal survey was performed, which showed an asymmetric lucency involving the left frontal calvarium extending to the superior lateral orbital rim. The brain MRI demonstrated a destructive avidly enhancing soft-tissue process which involved the superior left orbital rim likely with some degree of intracranial extension. This lesion exerts mass effect upon surrounding structures to the left ocular globe. With the skin and skeletal findings, the patient was diagnosed with LCH. His blood count was significant for thrombocytopenia. His liver and kidney function were normal. His electrolytes were also with in normal range. He was started on chemotherapy with vinblastine and systemic corticosteroids with resolution of the rash and decrease on the size of the lesion on the orbit within a few weeks.
Infantile LCH is a rare neoplastic disorder of hematopoietic myeloid precursor cells caused by activating mutations in the mitogen-activated protein kinase (MAPK) pathway, particularly BRAF-V600E mutation. White male children are mostly affected, with a peak incidence of 1-3 years of age. Nine out of 10 children with cutaneous involvement also have multisystemic disease, such as the case of our patient. LCH is classified as single or multisystem organ disease. Two-thirds of the cases present with single system involvement. Organs most commonly affected include the bone (the skull being the most commonly affected), skin, and high-risk organs like the liver, spleen, and bone marrow, and less commonly the lungs, lymph nodes, and central nervous system. Some patients can present with fever, lethargy, and weight loss. None were noted in our patient.
Skin findings of LCH can have multiple morphologies and presentations and often described as a big mimicker. In young infants like our patient, the seborrheic dermatitis–mimicking type is often seen. In other cases, the skin lesions can appear eczematous, petechial, with scabbing, crusting, or purpura. Xanthoma-like lesions, like that one our patient had in the back, have also been described. Resistant diaper dermatitis and cradle cap should prompt the clinician to think about LCH. Lesions can be so varied that can present with hypopigmentation (vitiligo like), hyperpigmentation, varicella-like papulo-pustules, and red blue nodules within others. Oral mucosa and nail involvement can also occur.
Bone involvement can present as soft-tissue mass with swelling and pain as it occur in our patient.
Endocrinopathies have been described in patients with LCH including diabetes insipidus, growth hormone deficiency, and less likely thyroid disease.