Leukemia cutis A dermal infiltrate of leukemic cells results in the papulonodular lesions, or plaques, that are illustrated here in Fig. 24-1. Such primary involvement of the skin is relatively rare in childhood leukemia. The wide variety of secondary manifestations of leukemia includes petechiae and ecchymoses and pyoderma gangrenosum.

In this example of congenital leukemia cutis, the violaceous nodule could easily be confused with a hemangioma or vascular malformation. In addition, Sweet’s syndrome (Fig. 16-24), an eruption of erythematous plaques, with a polymorphonuclear dermal infiltrate may be associated with leukemia. Also, children receiving chemotherapy are prone to bacterial and fungal infections of the skin, severe varicella, and ulcerative or chronic herpes simplex.

Hodgkin disease Like other lymphoproliferative disorders, Hodgkin disease may have both specific and nonspecific cutaneous manifestations. Figure 24-3 illustrates a relatively rare event in children with Hodgkin disease: the direct infiltration of malignant cells into the skin. A biopsy analysis of these brownish papules, nodules, and plaques reveals a histology similar to that of affected lymph nodes. These lesions may occasionally ulcerate, and pruritus is a distressing symptom.

Chloroma Also known as granulocytic sarcoma, this lesion may be seen in acute and chronic myelocytic leukemias. The lesions, which are infiltrates of masses of leukemic cells, occasionally present with a green color due to myeloperoxidase activity.

Neuroblastoma, metastatic This malignant tumor of the autonomic nervous system occurs most frequently in young children. Metastatic disease is often present at the time of diagnosis. Cutaneous metastases appear as bluish papules or nodules involving the trunk or extremities.

The lesions are sometimes noted to blanch upon stroking and may sometimes exhibit increased sweating. Children who are under 1 year of age at the time of diagnosis, as was the case in the patient in Fig. 24-6, may experience spontaneous regression of their illness. The prognosis in older children and in those with very widespread disease tends to be poor.

Langerhans cell disease This disorder is the result of a clonal proliferation of Langerhans cells and can involve a variety of organ systems. This is a spectrum of disease that encompasses acute disseminated LCD (formerly Letterer-Siwe disease), chronic multifocal LCD (formerly Hand-Schüller-Christian disease), and chronic focal LCD (eosinophilic granuloma). Figure 24-7 shows the characteristic skin involvement of Langerhans cell disease, which can present with a seborrheic-like, scaly, erythematous eruption on the scalp, face, and ears.

Figure 24-8 shows a more papular presentation, also in the scalp. Diagnosis is made with skin biopsy, which demonstrates the presence of large oval cells with S100 and CD1a positivity. In some cases, the presence of Birbeck granules on electron microscopy is used to confirm the diagnosis. Langerhans cell histiocytosis may be accompanied by hepatosplenomegaly, lymphadenopathy, anemia, and thrombocytopenia.