Isolated hypohidrosis: pathogenesis and treatment.

BACKGROUND: Hypohidrosis can result in heat injury, a potentially fatal condition. The majority of hypohidrosis cases have no associated abnormalities or secondary causes, and are termed "isolated hypohidrosis". These are clinically divided into miliaria profunda (MP), acquired idiopathic generalized anhidrosis (AIGA) and idiopathic partial hypohidrosis (IPH). The pathogenesis of isolated hypohidrosis remains largely unknown and there is no established effective treatment. OBJECTIVES: To elucidate the pathogenesis of isolated hypohidrosis using in vivo high-definition optical coherence tomography (HD-OCT) imaging and assess the therapeutic profile of oral retinoids for this condition. MATERIALS & METHODS: We conducted a retrospective analysis on all patients with isolated hypohidrosis in our neuro-dermatology clinic over a 5.75-year period. All patients routinely underwent standardised exercising and whole-body starch-iodine testing, followed by non-invasive HD-OCT skin imaging. Patients' demographics, disease characteristics, histology and treatment history were analysed. RESULTS: Of the 51 patients identified with isolated hypohidrosis; 23 were diagnosed with MP, 14 with AIGA, and 14 with IPH. In these patients, HD-OCT imaging led to the identification of sub-stratum corneal hypo-refractile material with underlying dilated sweat ducts, not present in healthy controls. The size of this material was most pronounced in MP, followed by AIGA, and then IPH. Post-treatment, the material decreased in size. Treatment response was reported in 90.6% patients with isotretinoin and 75.0% with acitretin. No recurrence has been reported to date. Side effects were largely anticipated and common. CONCLUSION: The pathogenesis of isolated hypohidrosis involves obstruction of sweat orifices at the stratum corneum. Treatment with oral retinoids, particularly isotretinoin, is effective and safe.

Polymorphism in the PER3 promoter associates with diurnal preference and delayed sleep phase disorder.

STUDY OBJECTIVES: To screen the PER3 promoter for polymorphisms and investigate the phenotypic associations of these polymorphisms with diurnal preference, delayed sleep phase disorder/syndrome (DSPD/DSPS), and their effects on reporter gene expression. DESIGN: Interspecific comparison was used to define the approximate extent of the PER3 promoter as the region between the transcriptional start site and nucleotide position -874. This region was screened in DNA pools using PCR and direct sequencing, which was also used to screen DNA from individual participants. The different promoter alleles were cloned into a luciferase expression vector and a deletion library created. Promoter activation was measured by chemiluminescence. SETTING: N/A. PATIENTS OR PARTICIPANTS: DNA samples were obtained from volunteers with defined diurnal preference (3 x 80, selected from a pool of 1,590), and DSPD patients (n=23). INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: We verified three single nucleotide polymorphisms (G -320T, C -319A, G -294A), and found a novel variable number tandem repeat (VNTR) polymorphism (-318 1/2 VNTR). The -320T and -319A alleles occurred more frequently in DSPD compared to morning (P = 0.042 for each) or evening types (P = 0.006 and 0.033). The allele combination TA2G was more prevalent in DSPD compared to morning (P 0.033) or evening types (P = 0.002). Luciferase expression driven by the TA2G combination was greater than for the more common GC2A (P < 0.05) and the rarer TA1G (P < 0.001) combinations. Deletion reporter constructs identified two enhancer regions (-703 to -605, and -283 to -80). CONCLUSIONS: Polymorphisms in the PER3 promoter could affect its expression, leading to potential differences in the observed functions of PER3.