Discussion
HTLV-1 is endemic in KZN with a reported seroprevalence of 2.6% in the Ngwelezana and of 3.35 in Ubombo (Tarin, 1997) both districts within the same province as Durban. The mean age of our cohort (8 years) was much older than reported in the Caribbean where IDH usually presents between the ages of 2 and 4 years. Perhaps the subtropical climate of South Africa could explain these differences or the disease may be less severe in the early stages resulting in late presentation. The clinical features of IDH in South Africa are similar to that described elsewhere. However, chronic nasal discharge and/or nasal crusting was much less common that expected, (a mandatory criteria for diagnosis). These findings support the suggestion by de Oliveira and Suite et al. who have contested the inclusion of nasal crusting as a major criterion for the diagnosis of IDH. Farre et al., in their evalution of 42 cases from Brazil, records the fact that not all but 30 of their 42 cases, from Brazil exhibited crusting of the nares, raising the same issue that crusting around the nostrils should not be mandatory in cases of IDH. There appears to be a major difference between the disease in South Africa and that in Senegal, Brazil and Jamaica.
Our cases had less severe IDH presentation than in the those from Senegal where lesions were more infective and crusted whereas the morphology of lesions in our study was more inflammatory than infective, (Figures 1 and 2). Complications have been reported in 30–35% of all patients with IDH. However, the cases in our series had a low complication rate (15.6%), none of the cases had other HTLV-1-related complications, such as HAM/TSP nor ATLL. The inconsistency in the presence of a generalized fine papular rash of the original description of IDH, taken together with our findings (the variation in presence of nasal crusting) appear to affirm Mahe and co-worker's speculation that there are minor variants of IDH which do not show all the features of full-blown IDH as reported in the literature. Clusters of IDH were observed in 4 of the 9 families in this study, reinforcing the hypothesis that HTLV-1 infection, in all but rare cases of IDH, is from mother to child. All six viruses were of the widely prevalent Cosmopolitan subtype A (HTLV-1 a), consistent with published data from KZN. We had to exclude nine patients with clinical manifestations of IDH who were co-infected with HIV. Interestingly these were all adults whereas IDH is considered a childhood disease. However, there have been case reports of IDH beginning in adult life. The lack of a published scoring system to assess severity of lesions in IDH makes comparison of the clinical appearances of lesions in those co-infected with HIV-1, difficult. It was therefore difficult to determine whether the co-infected cases were truly IDH, or HIV-related seborrhoeic dermatitis.
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Figure 1.
A typical patient with IDH showing exudative dermatitis with crusting on the face, scalp, external ear, and retro-auricular areas. a. also demonstrates crusted lesions on face together with blepharitis that characterises IDH in most patients. b. Shows an exudative dermatitis with crusting on the face, scalp, external ear, and retro-auricular areas.
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Figure 2.
Another patient with infective dermatitis, presenting with only some of the clinical features of IDH. a: Infective dermatitis patient with corneal opacities (b) that affect a proportion of patients with this condition, also demonstrating flexural involvement (c).
Except for the absence of anemia in our study population in contrast to the previous reports, other laboratory parameters were in keeping with what has been documented in the previous descriptions.
The data show that cases of IDH had a significantly high HTLV-1 proviral load (mean levels of 10.5%). It has been suggested that IDH act as a cofactor for the development of HTLV-1- associated diseases, such as HAM/TSP and ATLL but the mechanisms are still unclear. HTLV-1 proviral load levels is regarded as important predictor of ATLL and HAM/TSP. It would be interesting to follow all the identified cases with IDH over time and monitor the clinical evolution of the disease to determine if they develop any of the HTLV-1 associated conditions (ATLL, HAM/TSP).