Molecular implications of skin lesions in tuberous sclerosis

Perfect match: mTOR inhibitors and tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is an autosomal dominant syndrome that presents with diverse and complex clinical features and involves multiple human systems. TSC-related neurological abnormalities and organ dysfunction greatly affect the quality of life and can even result in death in patients with TSC. It is widely accepted that most TSC-related clinical manifestations are associated with hyperactivation of the mammalian target of rapamycin (mTOR) pathway caused by loss‑of‑function mutations in TSC1 or TSC2. Remarkable progress in basic and translational research has led to encouraging clinical advances. Although mTOR inhibitors (rapamycin/everolimus) demonstrate great potential in TSC management, two major concerns hamper their generalized application. One is the frequent manifestation of adverse events, such as stomatitis, infections, and menstrual disorders; and the other is the poor response in certain patients. Thus, indicators are required to effectively predict the efficacy of mTOR inhibitors. Herein, we have summarized the current utilization of mTOR inhibitors in the treatment of TSC and focused on their efficacy and safety, in an attempt to provide a reference to guide the treatment of TSC.

Hyperactivation of mammalian target of rapamycin (mTOR) is essential in the pathogenesis of tuberous sclerosis complex (TSC) and can serve as a therapeutic target.

mTOR inhibitors have shown considerable success in multiple clinical trials for the treatment of TSC, including neurological, pulmonary, cardiac, renal, and cutaneous phenotypes.

mTOR inhibitors are associated with adverse events, which should be considered during the management of TSC.

Indicators to predict mTOR inhibitor efficacy are required to select patients who are likely to benefit from such therapy.

Clinical spectrum of MTOR-related hypomelanosis of Ito with neurodevelopmental abnormalities

Purpose

Hypomelanosis of Ito (HI) is a skin marker of somatic mosaicism. Mosaic MTOR pathogenic variants have been reported in HI with brain overgrowth. We sought to delineate further the pigmentary skin phenotype and clinical spectrum of neurodevelopmental manifestations of MTOR-related HI.

Methods

From two cohorts totaling 71 patients with pigmentary mosaicism, we identified 14 patients with Blaschko-linear and one with flag-like pigmentation abnormalities, psychomotor impairment or seizures, and a postzygotic MTOR variant in skin. Patient records, including brain magnetic resonance image (MRI) were reviewed. Immunostaining (n = 3) for melanocyte markers and ultrastructural studies (n = 2) were performed on skin biopsies.

Results

MTOR variants were present in skin, but absent from blood in half of cases. In a patient (p.[Glu2419Lys] variant), phosphorylation of p70S6K was constitutively increased. In hypopigmented skin of two patients, we found a decrease in stage 4 melanosomes in melanocytes and keratinocytes. Most patients (80%) had macrocephaly or (hemi)megalencephaly on MRI.

Conclusion

MTOR-related HI is a recognizable neurocutaneous phenotype of patterned dyspigmentation, epilepsy, intellectual deficiency, and brain overgrowth, and a distinct subtype of hypomelanosis related to somatic mosaicism. Hypopigmentation may be due to a defect in melanogenesis, through mTORC1 activation, similar to hypochromic patches in tuberous sclerosis complex.

Graphical Abstract

Nd:YAG laser for "fractional" treatment of angiofibromas

BACKGROUND

Tuberous sclerosis is an autosomal dominant disorder with hamartomas in multiple organ systems. Facial angiofibromas (AF) are a common cutaneous manifestation of tuberous sclerosis. They may lead to significant cosmetic and psychological problems. Many treatment modalities have been used with variable satisfaction. Fractional photothermolysis (FP) is a novel concept of laser therapy, which induces non-contiguous microscopic thermal injury.

OBJECTIVE

This study was designed to evaluate the efficacy and side effects of Nd:YAG laser treatment for facial AF by using spot-like irradiation technique similar to FP.

MATERIALS AND METHODS

Twelve patients (skin types III-IV, aged 17-45 years) with facial AF received monthly treatment with Nd:YAG laser in a pinpoint coagulation fashion. Clinical improvements were evaluated in five categories. Side effects were monitored at each follow-up visit.

RESULTS

Excellent improvement was seen in 10 patients and good improvement in two at one month after the final treatment session. After 12 months of follow-up, no patient had significant recurrence of AF. Five patients were followed up for three years with few pinpoint-sized regrowth occurring; none of these patients received additional treatments. Side effects included transient erythema and edema in each patient but no bleeding, infection, dyspigmentation, or scarring.

CONCLUSIONS

The present study indicates that Nd:YAG laser is an effective and safe management for the fractional treatment of facial AF.

Trends in the prevalence of tuberous sclerosis complex manifestations: an epidemiological study of 166 Japanese patients

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder with multi-system involvement and variable manifestations. There has been significant progress in TSC research and the development of technologies used to diagnose this disorder. As a result, individuals with mild TSC are now being diagnosed, including many older adults who have not developed seizures or cognitive abnormalities. We conducted a statistical analysis of the frequency of TSC manifestations in a population of Japanese adults and children, comparing our findings with historical data. The chi-square test was used to examine the frequency of each manifestation by age. A total of 166 outpatients at the Department of Dermatology of Osaka University Hospital during the period from January 2001 to March 2011 were included in the study. Compared to previous reports, the frequency of neurologic manifestations (excepting autism) was lower in this cohort, and the frequency of skin manifestations (excepting hypomelanotic macules) was higher in this cohort. The frequencies of pulmonary lymphangioleiomyomatosis and renal manifestations were not significantly different from those previously reported. Regarding the association of each manifestation with age, the frequency of neurologic manifestations (excepting subependymal giant cell astrocytoma) was significantly higher in younger patients than in older patients. The frequency of skin manifestations and renal angiomyolipoma were significantly higher in older patients than in younger patients. Because of their high frequency and visibility, skin manifestations are useful in the diagnosis of TSC. Moreover, uterine perivascular epithelioid cell tumor was also characterized as a new findings associated with TSC.

Connective tissue nevi in children: institutional experience and review

BACKGROUND

Connective tissue nevi (CTN) are circumscribed hamartomas of the skin in which there is an abnormal mixture of normal components of the dermis that may be sporadic or associated with syndromes such as Buschke-Ollendorff, tuberous sclerosis, and Proteus.

OBJECTIVE

We sought to specify the clinical and histologic features of CTN in childhood and to propose a diagnostic approach and updated classification.

METHODS

This was a retrospective study in a tertiary pediatric outpatient population, accessing clinical and histopathological records.

RESULTS

We classified 114 cases of CTN from 1980 to 2008.

LIMITATIONS

The majority of cases were confirmed by histopathological examination. Therefore, our series excludes many CTN that were not biopsied. In addition, follow-up was variable.

CONCLUSION

Our series demonstrates the usefulness of a modified classification for CTN. Biopsy should be done when clinical diagnosis is uncertain, or in multiple lesions. When biopsy is performed it should include normal-appearing skin for comparison and, in Buschke-Ollendorff syndrome, limited anterior-posterior x-rays of the hands, wrists, feet, ankles, knees, and pelvis instead of a full skeletal survey.

Giant angiofibromas in tuberous sclerosis complex: a possible role for localized lymphedema in their pathogenesis

BACKGROUND

Giant angiofibromas in patients with tuberous sclerosis complex (TSC) are rare.

OBJECTIVE

We sought to report two patients who had TSC with unusually large and disfiguring facial angiofibromas and to identify underlying histopathologic changes that may possibly explain the clinical features.

METHODS

We performed a clinicopathologic, immunohistochemical, and molecular biologic study using 42 lesional specimens and peripheral blood from one of the two patients. The immunohistochemical investigations were mainly focused on the vascular moiety of the lesions. TSC1 and TSC2 alterations were studied using multiplex ligation-dependent probe amplification for large deletion/duplication mutations, whereas screening for small mutations was performed using polymerase chain reaction amplification of individual coding exons and exon-intron junctions of both genes followed by an analysis on denaturation gradient gel electrophoresis.

RESULTS

Histopathologic examination revealed, in addition to findings typical of angiofibroma, several unusual features including multinucleated giant cells containing multiple intracytoplasmic vacuoles, Touton-like cells, emperipolesis, pagetoid dyskeratosis, vacuolar alteration at the dermoepidermal junction, Civatte bodies, and melanophages in the subjacent dermis. Numerous dilated lymphatic vessels were detected indicating localized lymphostasis, probably caused by secondary lymphedema. The lymphatic nature of the vessels was confirmed by immunohistochemical study. Genetic testing for TSC1 and TSC2 gene mutations revealed a substitution on position c.2251C>T resulting in a nonsense mutation R751X in fragment 20.2.

LIMITATIONS

Histopathologic specimens and peripheral blood were available from only one patient.

CONCLUSION

Localized lymphedema may contribute to the formation of large disfiguring angiofibromas in patients with TSC.