11.12.6 Langerhans' cell histiocytosis
Langerhans' cell histiocytosis (LCH) is a non-malignant granulomatous, childhood
disorder that is characterized pathologically by uncontrolled proliferation and
accumulation of Langerhans' cells, mixed with varying proportions of eosinophils and
multinucleated giant cells. LCH replaced the term 'histiocytosis X' and the closely
related syndromes eosinophilic granuloma, Hand-Schuller-Christian disease, and
Letterer-Siwe disease. The clinical hallmark of LCH is the presence of lytic bone
lesions that may be single or multiple. When lesions are widespread they can affect
the pituitary gland and retro-orbital region, thus causing diabetes insipidus and
exophthalmos, respectively. The disseminated form of LCH is extremely aggressive
and has a poor prognosis. It is often diagnosed in the first 6 months of life before
becoming widespread by about 3 years of age.
The periodontal manifestations of LCH may be the presenting signs, which include a
marginal gingivitis, bleeding gingiva, abscess formation, pain, and drifting and
mobility of the teeth. Radiographs show localized or generalized bone loss,
characteristic osteolytic lesions, and 'floating teeth' with no alveolar bone support
(642HFig. 11.17).
A biopsy will confirm the diagnosis and a full radiographic screening determines the
severity of the syndrome. Local lesions that are confined to bone respond well to
curettage and excision. The mortality rate increases in the more widely disseminated
forms of the syndrome and when overlying soft tissues are involved. Treatment is by
radiotherapy and chemotherapy.
643H
Fig. 11.17 Extensive bone loss around
mandibular left premolars in a 15-year-
old child with Langerhans cell
histiocytosis. (Reproduced by kind
permission of Dr I. L. Chapple, Professor
of Periodontology, Birmingham, UK.)11.12.7 Hypophosphatasia
Hypophosphatasia is a rare, inborn error of metabolism characterized by defective
bone mineralization, a deficiency of alkaline phosphatase (ALP) activity, and an
increased excretion of phosphoethanolamine in the urine. ALP plays a major part in
the mineralization of hard tissues and so the absence of the enzyme predisposes to a
range of bone and cartilage defects. The condition is an autosomal-recessive trait,
although the inheritance pattern of some milder forms of hypophosphatasia may be
autosomal-dominant.
Key Points