[Acquired regressive cutaneous non-Langerhans-cell histiocytosis in an infant]. / Histiocytose cutanée acquise régressive non langerhansienne de l'enfant.

INTRODUCTION: Cutaneous histiocytosis of childhood often regresses spontaneously without treatment. In some cases however, it is difficult to differentiate aggressive forms and electron microscopy and immunohistochemistry can be a valuable help. We report a case of cutaneous histiocytosis in a child which illustrates the difficulties encountered in the classification of histiocytosis. CASE REPORT: An 18-month old girl was brought to consultation with a cutaneous nodule which had developed at the age of 15 months on the labia majora. A second nodule on the chin had regressed spontaneously. Histology showed evidence of dermal histiocyte proliferation. Immunohistochemistry demonstrated is non Langerhans nature which was confirmed by electron microscopy. The clinical course was benign after surgical exeresis of the lesion on the labia majora. DISCUSSION: Different forms of histiocytosis can be classed on the basis of 4 criteria: Langerhans origin or not, acquired or congenital forms, cutaneous or visceral involvement, benign or malignant course. Four diagnosis were possible in our case: histiocytosis X, self-healing congenital histiocytosis, benign cephalic histiocytosis, juvenile xanthogranuloma. We preferred to use the descriptive term of acquired regressive cutaneous non-X histiocytosis of childhood.

Fabry's disease: heterozygous form of different expression in two monozygous twin sisters.

A 26-year-old woman presented widespread angiokeratomas predominantly in a swimsuit distribution pattern associated with acroparesthesia in all four limbs. The tentative diagnosis of Fabry's disease (FD) was confirmed by optical and electron-microscopic findings and by appropriate biochemical testing. The work-up showed ocular and renal manifestations of the disease. The monozygous twin sister of the patient was asymptomatic although she was shown to be heterozygous for the enzymatic defect. These 2 cases illustrate the concept of extreme lyonization which can explain observed phenotypic differences in heterozygous females with X-linked hereditary diseases. The father and mother of the patient were shown to be noncarriers of the trait, suggesting de novo mutation in the twin pregnancy. However, biochemical testing for the detection of FD heterozygous females cannot rule out the possibility of the mother being heterozygous with normal enzyme activity.