[Extensive Mongolian spot related to Hurler disease]

We report a case of a large blue mongolian spot which led to early diagnosis of Hurler's syndrome. This association is uncommon and should be recognized by dermatologists for early diagnosis and management.

A male infant from Guinea, born to first-cousin parents, was seen at the age of 4.5 months for multiple, particularly extensive blue mongolian spots. Growth was +2 SD for age and the infant's psychomotor development was normal. A slight thickening of the skin was noticed without real dysmorphism. The blue spots extended over the entire posterior aspect and part of the anterior aspect of the trunk and involved all four limbs and the eyelids. The elbow and knee joints were moderately stiff and liver enlargement was palpated. The skin biopsy showed fusiform cells with melanin pigment tattooing the cytoplasm. No vacuolized epidermal cells were observed. Blood cell counts and liver and kidney tests were normal. Tests were positive for vacuolized lymphocytes and Gasser lymphocytes. Urine was positive for mucopolysaccharides and the enzymology study showed an alpha-L-iduronidase deficiency in serum and leukocytes, confirming the diagnosis of Hurler's disease. As no HLA compatible donor was available, no bone marrow graft was attempted. The child is a candidate for organoid gene therapy.

Mongolian spots predominate in Asian, American Indian and black population (90% of the cases) compared with Caucasians (10%). The pathogenesis and pathogenic associations are unknown. The incidence of large widespread mongolian spots is also unknown and no precise criteria are available to define this entity. A few cases of extended mongolian spots associated with type 1 gangliosidosis and about 20 cases associated with Hurler's disease have been reported in the literature. The association with Hurler's disease is probably not fortuitous and several hypotheses have been put forward. Bone marrow transplantation can improve prognosis if performed early before onset of irreversible visceral disorders, emphasizing the importance of early diagnosis in children.