Transthyretin Amyloidosis: Chaperone Concentration Changes and Increased Proteolysis in the Pathway to Disease

Transthyretin amyloidosis is a conformational pathology characterized by the extracellular formation of amyloid deposits and the progressive impairment of the peripheral nervous system. Point mutations in this tetrameric plasma protein decrease its stability and are linked to disease onset and progression. Since non-mutated transthyretin also forms amyloid in systemic senile amyloidosis and some mutation bearers are asymptomatic throughout their lives, non-genetic factors must also be involved in transthyretin amyloidosis. We discovered, using a differential proteomics approach, that extracellular chaperones such as fibrinogen, clusterin, haptoglobin, alpha-1-anti-trypsin and 2-macroglobulin are overrepresented in transthyretin amyloidosis. Our data shows that a complex network of extracellular chaperones are over represented in human plasma and we speculate that they act synergistically to cope with amyloid prone proteins. Proteostasis may thus be as important as point mutations in transthyretin amyloidosis.

Variant Rett Syndrome in a Girl with a Pericentric X-Chromosome Inversion Leading to Epigenetic Changes and Overexpression of the MECP2 Gene

Rett syndrome is a neurodevelopmental disorder caused by mutations in the MECP2 gene. We investigated the genetic basis of disease in a female patient with a Rett-like clinical. Karyotype analysis revealed a pericentric inversion in the X chromosome -46,X,inv(X)(p22.1q28), with breakpoints in the cytobands where the MECP2 and CDKL5 genes are located. FISH analysis revealed that the MECP2 gene is not dislocated by the inversion. However, and in spite of a balanced pattern of X inactivation, this patient displayed hypomethylation and an overexpression of the MECP2 gene at the mRNA level in the lymphocytes (mean fold change: 2.55±0.38) in comparison to a group of control individuals; the expression of the CDKL5 gene was similar to that of controls (mean fold change: 0.98±0.10). No gains or losses were detected in the breakpoint regions encompassing known or suspected transcription regulatory elements. We propose that the de-regulation of MECP2 expression in this patient may be due to alterations in long-range genomic interactions caused by the inversion and hypothesize that this type of epigenetic de-regulation of the MECP2 may be present in other RTT-like patients.

TINU syndrome – Two Clinical Cases of Tubulo-Interstitial Nephritis and Uveitis

TINU (Tubulo-Interstitial Nephritis and Uveitis)syndrome is a rare disease of unknown aetiology characterised by the association between interstitial nephritis and uveitis. The authors present the cases of two young children whose symptoms began with anorexia and weight loss, associated with renal failure and proteinuria of tubular origin. One child also presented anaemia, glycosuria without hyperglycaemia and microhaematuria. A few months later both developed uveitis. In both cases the renal biopsy showed changes compatible with interstitial nephritis. As interstitial nephritis and uveitis aetiologies were not identified, TINU syndrome was suggested as a possible diagnosis. In both children there was a complete resolution, with one needing systemic steroids and immunosuppressive treatment. TINU syndrome should always be considered in the differential diagnosis of patients with renal and ophthalmologic changes.

Autoimmune Thyroiditis Presenting as Palmoplantar Keratoderma

Palmoplantar keratoderma is a heterogeneous group of hereditary and acquired disorders characterized by abnormal thickening of palms and soles. Hypothyroidism is an unusual cause of palmoplantar keratoderma, rarely reported in the literature. We report a case of a 43-year-old woman presented with a 3-month history of a diffuse palmoplantar hyperkeratosis unresponsive to topical keratolytics and corticosteroids. Her past medical and family histories were unremarkable. She complained of recent asthenia, mood changes and constipation. Laboratory evaluation revealed an autoimmune thyroiditis with hypothyroidism. Other causes of acquired palmoplantar keratoderma were excluded. After hormonal replacement therapy institution, a gradual improvement of skin condition was observed. The diagnosis of underlying causes for acquired palmoplantar keratoderma can be a difficult task; however its recognition is essential for successful treatment results. Although a very rare association, hypothyroidism must be suspected in patients with acquired palmoplantar keratoderma, particularly when it occurs in association with systemic symptoms.