Objectives: To review the literature on diseases linked with infection by human T-cell lymphotropic virus type I (HTLV-I) in childhood and adolescence, with focus on clinical aspects, diagnosis, pathogenesis, progression and treatment.Sources: Medical literature published during the last 20 years identified using PubMed and MEDLINE and from specialized medical books, with emphasis on infective dermatitis associated with HTLV-I (IDH), on the juvenile form of HTLV-associated myelopathy/tropical spastic paraparesis (HAM/TSP), on adult T-cell leukemia/lymphoma (ATL) and on HTLV-I-associated uveitis. Keywords used to search databases were: HTLV-I-associated infective dermatitis, HTLV-Iassociated myelopathy/tropical spastic paraparesis, adult T-cell leukemia/lymphoma, HTLV-I-associated uveitis.Summary of the findings: IDH is a chronic, relapsing and infected dermatitis of childhood which always involves the scalp and which may progress to HAM/TSP and ATL. HAM/TSP is a chronic and incapacitating myelopathy of adults. There are 17 well-documented cases of HAM/TSP in children and adolescents in the literature, 12 of whom are patients with IDH. In contrast with the adult form of the disease, the juvenile form is rapid and progressive. ATL is a type of T-cell leukemia/ lymphoma that affects adults and is generally fatal. Eleven of the 24 published reports of ATL in children and adolescents were diagnosed in Brazil.Conclusions: These diseases are likely to be more common in childhood and adolescence than the literature would suggest. It is advisable that serological testing be performed for HTLV-I in children and adolescents suffering from chronic and relapsing eczema, with signs and symptoms of myelopathy or with a diagnosis of T-cell leukemia/lymphoma. It is important that pediatricians know how to recognize the pediatric manifestations of this infection in order to correctly diagnose them and offer their patients appropriate guidance and treatment.

The onset of IDH may occur earlier than reported in the literature. The scalp and retroauricular regions are always affected, and lesions are invariably present in ≥3 areas. Crusting of the nostrils cannot be considered an obligatory factor for the diagnosis of IDH. The recurring nature of IDH was a characteristic found in all cases. Patients with classic IDH lesions who are serologically negative should be investigated by PCR. Therefore, the indispensable criteria for diagnosis are (1) presence of erythematous-scaly, exudative, and crusted lesions involving ≥3 areas, including the scalp and retroauricular regions; (2) recurring nature of the lesions; and (3) a finding of HTLV-1 infection by serology or molecular biology.

A strong association was observed between IDH and HAM/TSP. The familial clustering of both diseases suggests a genetic background. Serological screening for HTLV-1 in children with symptoms of myelopathy is essential in areas where HTLV-1 is endemic.

We describe a patient with human T cell lymphotropic virus type 1 (HTLV-1)-associated infective dermatitis who developed HTLV-1-associated myelopathy/tropical spastic paraparesis and adult T cell leukemia/lymphoma at 16 years of age. Long inverse polymerase chain reaction was used to demonstrate monoclonal integration of proviral DNA in the lymphomatous skin lesion.

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The juvenile HAM/TSP may occur very early and also presents marked female predominance. Progression of IDH to HAM/TSP before 19 years of age is frequent (54%). Rapid progressive form may also occur in early HAM/TSP. As juvenile IDH and HAM/TSP are due to vertical transmission through breastfeeding, it is very important to avoid this pathway of infection.

Fifteen families with clustering of infective dermatitis associated with HTLV-1 (IDH) and/or HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP) were observed among 28 families of IDH index cases, 93% of them occurring in two generations. With the exception of two mothers of children with IDH, all the mothers with HAM/TSP had at least one child with HAM/TSP. This is the first report of such clustering involving many families.

This is the first report on the presence of flower cells in HTLV-1-infected children and adolescents. Furthermore, these cells have not previously been reported in IDH patients. The cases with flower cells probably represent precursory ATL cases, these patients being at a greater risk of developing ATL.