Histiocytosis syndromes in children

Atypical cellular disorders

Atypical cellular disorders are commonly considered part of the gray zone linking oncology to hematology and immunology. Although these disorders are relatively uncommon, they often represent significant clinical problems, provide an opportunity to understand basic disease mechanisms, and serve as model systems for the development of novel targeted therapies. This chapter focuses on such disorders. In Section I, Dr. Arceci discusses the pathogenesis of Langerhans cell histiocytosis (LCH) in terms of the hypothesis that this disorder represents an atypical myeloproliferative syndrome. The clinical manifestations and treatment of LCH in children and adults is discussed along with possible future therapeutic approaches based upon biological considerations. In Section II, Dr. Longley considers the molecular changes in the c-Kit receptor that form the basis of mastocytosis. Based on the location and function of c-Kit mutations, he develops a paradigm for the development of specific, targeted therapies. In Section III, Dr. Emanuel provides a review of the "mixed myeloproliferative and myelodysplastic disorders," including novel therapeutic approaches based on aberrant pathogenetic mechanisms. Taken together, these chapters should provide an overview of the biological basis for these disorders, their clinical manifestations, and new therapeutic approaches.

Liver involvement in childhood histiocytic syndromes

The histiocytic syndromes of childhood are disorders of the reticuloendothelial system with variable clinical manifestations. Included among them are Langerhans cell histiocytosis and hemophagocytic lymphohistiocytosis. This discussion will be restricted to these two disorders. Liver disease in these conditions is common. Langerhans cell histiocytosis is characterized by the abnormal clonal proliferation of the macrophage-derived Langerhans cell. Liver involvement at diagnosis has management and prognostic significance. In a subgroup of patients, sclerosing cholangitis develops, which may lead to end-stage liver disease requiring liver transplantation. Hemophagocytic lymphohistiocytosis is a disease of abnormally activated macrophages that can involve multiple organ systems, including the liver. Differentiation between this disorder and other causes of pediatric liver disease is critical, because treatment strategies include chemotherapy, immunosuppression, and frequently bone marrow transplantation.

Defective natural killer cell function in patients with hemophagocytic lymphohistiocytosis and in first degree relatives

Hemophagocytic lymphohistiocytosis (HLH), also referred to as familial erythrophagocytic lymphohistiocytosis, is a rare disorder of infancy associated with proliferation of activated histiocytes and T cells, anemia, thrombocytopenia, and fevers. This disorder appears to be due to the uncontrolled activation of T cells producing IL-2, tumor necrosis factor-alpha, and interferon-gamma. Untreated, the disorder is universally fatal. Various deficits in immune function have been described during acute disease activity including impaired T cell function, impaired monocyte-mediated antibody-dependent cytotoxicity, impaired natural killer cell function, and impaired IL-1 production. We examined natural killer cell function in familial HLH patients to determine whether this finding was consistently associated with the disease. We also examined natural killer cell function in asymptomatic parents and siblings of patients. Impaired natural killer cell function was identified in all patients and in some family members, including obligate carrier parents. This implies that one potential genetic defect in HLH may result in depressed natural killer function, but that this may not be sufficient to reliably predict eventual progression to disease.

Clinical aspects of Langerhans cell histiocytosis

Langerhans cell histiocytosis remains an enigmatic disease with protean manifestations. It may be self-limited in some, whereas in others, even intensive treatment is unsuccessful. The outcome depends on whether vital organ function is compromised at diagnosis or shortly thereafter, in which case the prognosis is grave.

Sonographic appearance of hepatic Langerhans cell histiocytosis

Periportal lesions were detected on ultrasound in two cases of Langerhans cell histiocytosis with liver involvement. Hypoechoic or hyperechoic lesions were detected in different stages of evolution. Hyperechoic lesions probably corresponded to periportal inflammation whilst hyperechogenicity suggested xanthomatous change.

Functional defect in cells involved in Langerhans cell histiocytosis

The characteristic cell type involved in Langerhans cell histiocytosis, 'LCH cells', express most of the enzyme histochemical and immunocytochemical markers of normal epidermal Langerhans cells. It is not known, however, whether these LCH cells express the functional characteristics of normal epidermal Langerhans cells. We studied the alloantigen-presenting activity of LCH cells derived from lesional sites of three patients with the disease. Lesional cells expressing the CD1a molecule were enriched using either fluorescein-activated cell sorting or negative selection with indirect immunomagnetic beads, and functional activity was assessed using the 6-day primary allogeneic mixed-cell reaction. Compared to epidermal Langerhans cells from healthy controls, LCH cells showed minimal alloantigen-presenting activity on a per-cell basis. The diminished activity was not reversed by exogenous prostaglandin synthetase inhibitor or recombinant human IL-1 beta. This study confirms our previous report of a child, with fatal multisystem Langerhans cell histiocytosis suggesting that this disease represents a condition in which functionally defective cells of Langerhans cell phenotype accumulate and/or proliferate in various tissues. We postulate that the functional defect is a primary defect of these LCH cells that have acquired an as-yet-undetermined biological insult(s).

Defective alloantigen-presenting capacity of 'Langerhans cell histiocytosis cells'

The functional activity of skin cells derived from an infant who died of multisystem Langerhans cell histiocytosis (LCH) was examined. Involved and non-involved skin was obtained at postmortem examination within three hours of death; normal epidermal Langerhans cells and 'LCH cells' were separated by means of dispase digestion. The functional activity of different populations of CD1a positive cells was assessed using the conventional six day allogeneic mixed cell reaction. Compared with Langerhans cells from a healthy control, LCH cells showed minimal functional activity. However, Langerhans cells from non-involved skin showed normal and Langerhans cells overlying involved skin showed augmented functional activity. These findings suggest that LCH is a disease in which abnormal Langerhans cells accumulate and/or proliferate in various tissues but it does not affect the entire Langerhans cell population.

International variations in the incidence of childhood lymphomas

The International Agency for Research on Cancer has coordinated a worldwide study of childhood cancer incidence, with data provided by contributors from over 50 countries. We present here the results on lymphomas from this study and other sources. Hodgkin's disease had a relatively high incidence in North Africa and West Asia and a low incidence throughout East Asia. In populations of predominantly European origin, the highest rates tended to be in warmer countries of lower latitude. In industrialised Western countries, the incidence increased steeply with age and was low in childhood compared with that in young adults whereas elsewhere the increase in incidence between childhood and adults aged 20-34 was much less marked. The age-distribution of Hodgkin's disease in childhood appears to be related to levels of socio-economic development but the total incidence seems to be determined more by ethnic and environmental factors. The highest incidence of Burkitt's lymphoma occurred in tropical Africa and Papua New Guinea. Elsewhere, Burkitt's lymphoma was rare, though the incidence was higher in Spain, North Africa and the Middle East than in other areas. In most Western countries, a third of all non-Hodgkin lymphomas may be Burkitt's. There was no consistent pattern in the incidence of other non-Hodgkin lymphomas except for a tendency towards higher rates around the Mediterranean and in some Latin American registries.

Radiation therapy in the management of Langerhans cell histiocytosis

Twenty-two patients with Langerhans cell histiocytosis (LCH) were managed in the UCLA Department of Radiation Oncology from 1974 to 1987. Their median age was 17 years (range 1-42 years) and median followup 4.5 years (range 1-13 years). Fourteen patients had disease localized to a bone (13) or a soft tissue (one). Eight patients had LCH involving multiple bones (3) or soft tissues plus bones (5). Nine of 10 patients less than 19 years old had disease confined to bone(s) compared to 7 of 12 older patients. Fifty-six sites of LCH (40 bone, 16 soft tissue) were irradiated. Pediatric patients received therapy to 15 sites (14 bone, 1 soft tissue) and adults 41 sites (26 bone, 15 soft tissue). Median dose for bone lesions was 900 cGy (range 600-1,500) and for soft tissue 1,500 cGy (range 600-2,600). Local control was achieved in 46 of 56 sites (82%). Control rates for bone and soft tissue lesions were 35 of 40 (88%) and 11 of 16 (69%), respectively. Fifteen of 15 sites in pediatric patients were controlled compared to 29 of 41 (72%) in adults. Ten sites (18%) recurred 10 months to 4 years after irradiation. Recurrences were in-field and noted only in adults with involvement of multiple soft tissues plus bones. All recurrent soft tissue lesions had been treated with orthovoltage. Five patients developed new foci of LCH subsequent to irradiation. Four of these patients had disease involving soft tissues and bones. One patient with progressive LCH initially presented with a single bone lesion. The acute and chronic effects of radiation therapy were minimal. One patient suffered transient enlargement of adenopathy. An elevated serum TSH level was detected 9 years after irradiation of a cervical vertebra in another patient.

Histiocytosis X Langerhans cells react with antiinterleukin-2 receptor monoclonal antibody

Immunohistochemical study of 7 cases of histiocytosis X (HX) and of histologically normal skin shows that HX Langerhans cells react with Bl.49.9 monoclonal antibody which recognizes the Interleukin-2 receptor, whereas normal skin Langerhans cells do not. This reactivity suggest activation of HX Langerhans cells.