[Mannosidosis: a simple diagnosis].

Mannosidosis is a new and rare disorder. The following clinical symptoms should evolve its diagnosis: facial dysmorphy with slight mental retardation; bone deformities with abnormal L2 vertebra and craniosynostosis; biological abnormalities with vacuolized lymphocytes and absence of urinary mucopolysaccharides. Definite diagnosis relies upon detection of mannose oligosaccharides in the urine and serum deficiency of alpha-D-mannosidase.