Bone lesions in Langerhans cell histiocytosis

Insights into the pathogenesis of Langerhans cell histiocytosis: the development of targeted therapies

More than a century after its first description, Langerhans cell histiocytosis (LCH) still remains an intriguing disease. Considerable progress in understanding its biology has been achieved recently. Description of the V600E BRAF mutation in samples of LCH tissue in 2010 was followed by description of additional mutations, all leading to constitutive ERK activation. Current experimental data suggest that LCH is a myeloid neoplasia with inflammatory properties, yet the exact pathophysiology remains poorly understood. Disease management paradigms have changed over time, closely reflecting the evolving view of the nature of the disease. The international Histiocyte Society have conducted three prospective clinical studies on multisystem LCH since the early 1990s. The standard frontline therapy for patients with multisystem LCH based on the cumulative knowledge of those trials consists of 6–12 weeks of initial therapy (daily oral steroids and weekly vinblastine injections), followed by pulses of prednisolone/vinblastine every 3 weeks, for a total treatment duration of 12 months. A currently ongoing study (LCH-IV) with a complex design (five interventional and two observational strata) targets further reduction of mortality and morbidity by tailoring treatment intensity depending on expected risk, as well as by exploring treatment regimens for special locations. Current knowledge on LCH pathobiology opens opportunities for improvement in the patient outcome. The activating BRAF and MAP2K1 mutations collectively accounting for about 75% of the LCH population as well as the resulting constitutive activation of downstream ERK offer an opportunity for targeted treatment. Related issues (eg, finding most effective and less toxic drugs or combinations, appropriate dosage, and optimal treatment duration) must be addressed in controlled prospective trials. Additional mechanisms, such as the interactions of the mutated dendritic cell clone with other inflammatory cells and key cytokines and chemokines, still remain attractive targets for therapeutic intervention, particularly in patients with localized, less aggressive disease.

Pattern and course of single-system disease in Langerhans cell histiocytosis data from the DAL-HX 83- and 90-study

BACKGROUND

Single-system (SS) disease is the most common presentation in Langerhans cell histiocytosis (LCH) with a heterogenous clinical picture and course. Mostly bone and rarely skin or lymph nodes are involved.

PROCEDURE

One hundred and seventy patients with SS-LCH were registered in the DAL-HX 83/90 studies. They were diagnosed according to uniform diagnostic criteria and followed by a standardised schedule.

RESULTS

Single bone lesions were most common (68%), followed by multiple bone lesions (19%), isolated skin disease (11%), and isolated lymph node involvement (4 patients). In the detection of bone lesions radiographic skeletal survey proved to be superior to bone scan (97% vs. 82%). Treatment comprised surgery, irradiation and local instillation of steroids, and standardised chemotherapy for multifocal bone disease. After initial therapy 81% of the patients remained disease free. Reactivations restricted to the skeleton occurred in 18% of both unifocal and multifocal bone disease. Two skin patients had a chronic course. Fatality occurred only in one infant with skin disease who progressed to multi-system disease. Twenty-five percent of all patients developed permanent consequences, which were already present at diagnosis in about half of these patients and comprised mainly orthopedic problems related to lesional sites. Diabetes insipidus occurred in 3% and anterior pituitary dysfunction in 2% of the patients.

CONCLUSIONS

The course in SS%LCH was benign. In bone disease reactivations remained restricted to the skeleton and did not influence survival. However, reactivations had an impact on morbidity, as permanent consequences were mostly related to the site of disease activity. Med Pediatr Oncol 2001;37:108-114.

Langerhans cell histiocytosis with orbital involvement

PURPOSE

To review three cases of Langerhans cell histiocytosis with orbital involvement that represent a significantly excessive incidence of this rare disease in one community. Current diagnostic criteria and therapeutic modalities related to Langerhans cell histiocytosis are reviewed.

METHODS

Case reports. We present clinical, radiologic, histopathologic, and epidemiologic information on three patients with Langerhans cell histiocytosis.

RESULTS

All three children, born within 18 months of one another, manifested rapidly progressive unilateral proptosis at age 2 years. By computed tomography, all had moderately enhancing lesions with involvement of the sphenoid bone and lateral orbit as well as the temporal lobe of the brain. All patients were treated with a combination of vincristine and prednisone, with variable resolution of their lesions. The occurrence of three cases in children born in Nogales, Arizona/ Mexico, suggests an incidence rate of 40 per million, which is approximately 26 times the expected rate (P = .0001).

CONCLUSIONS

The extraordinarily high incidence and the concentration of cases in both time and space of this cluster implies that Langerhans cell histiocytosis may be a sentinel disease for unusual environmental exposures.

Radiographic skeletal survey and radionuclide bone scan in Langerhans cell histiocytosis of bone

BACKGROUND

The lack of a consensus in the literature on the imaging strategy in Langerhans cell histiocytosis (LCH) bone lesions in childhood.

OBJECTIVE

To evaluate the relative value of radionuclide bone scan (RBS) and radiographic skeletal survey (RSS) in the detection of LCH bone lesions, both in the initial work-up of the disease and during the follow-up period.

MATERIALS AND METHODS

Ten children with bone lesions evaluated by means of RSS and RBS in a retrospective study (1984-1993).

RESULTS

Fifty radiologically and/or scintigraphically abnormal foci were detected: 27 anomalies in the initial work-up (12 by both RSS and RBS, 8 by RSS only and 7 by RBS only) and 23 additional anomalies during follow-up (10 by both RSS and RBS, 10 by RSS only and 3 by RBS only). RSS+/RBS- lesions (n = 18) are more frequently encountered in the skull (P = 0.038), and more frequently lack radiologic signs of osteoblastic activity (P = 0.020), than RSS+/RBS+ lesions (n = 22). RSS-/ RBS+ abnormalities (n = 10) were most frequently insignificant.

CONCLUSION

In the initial work-up both RSS and RBS should be carried out, while in the follow-up only RSS should be performed.