Cerebrospinal Fluid Synaptic Proteins as Useful Biomarkers in Tyrosine Hydroxylase Deficiency

Tyrosine hydroxylase (TH) deficiency is an inborn error of dopamine biosynthesis and a cause of early parkinsonism. Two clinical phenotypes have been described. Type “B”: early onset severe encephalopathy; type “A”: later onset, less severe and better response to L-dopa. We aimed to study the expression of several key dopaminergic and gabaergic synaptic proteins in the cerebrospinal fluid (CSF) of a series of patients with TH deficiency and their possible relation with the clinical phenotype and response to L-DOPA. Dopamine transporter (DAT), D2-receptor and vesicularmonoamine transporter (VMAT2)weremeasured in the CSF of 10 subjectswith THdeficiency byWestern blot analysis. In 3 patients, data of pre- and post-treatmentwith L-DOPA were available, and in one of them, GABA vesicular transporter was determined. Results were compared to an age-matched control population. The concentration of D2-receptors in CSFwas significantly higher in patients with TH deficiency than in controls. Similarly, DAT and vesicular monoamine transporter type 2 were up-regulated. Studies performed before LDOPA, and on L-DOPA therapy showed a paradoxical response with D2 receptor expression increase as L-Dopa doses and homovanillic concentration gradually raised in a B phenotype patient. The opposite results were found in two patients with A phenotype. However, this is a very small sample, and further studies are needed to conclude robust differences between phenotypes. Synaptic proteins are detectable in the CSF and their quantification can be useful for understanding the pathophysiology of neurotransmitter defects and potentially to adjust and personalize treatments in the future.

Imunodeficiência Combinada Severa por Défice da Proteína RAG2

O défice da proteína do gene activador da recombinase resulta numa incapacidade de formação de antigénios por deficiente recombinação, o que se traduz por uma ausência quase completa de marcadores T e B nas populações linfocitárias com aumento relativo de marcadores NK. Clínicamente esta alteração revela-se como uma Imunodeficiência Combinada Severa de particular gravidade. Sem a realização precoce de transplante medular de um dador compatível a mortalidade é de 100% aos 2 anos de idade. Descrevemos um caso de um lactente, filho de pais consaguíneos, internado no nosso hospital, aos 6 meses de vida por síndrome hemolítico-urémico na sequência de pneumonia pneumocócica com derrame. Após terapia inyensiva verifica-se recuperação total da função renal mas desnutrição importante. A evolução posterior é caracterizada por infecções recorrentes, escaras cutâneas e agravamento da desnutrição. Laboratorialmente apresenta leucopénia e linfopénia persistente com valores muito baixos das imunoglobulinas séricas e ausência quase total das populações B. O estudo genérico revela existência de um défice proteico do gene activador da recombinase (RAG)2. Foi possível a exclusão da mesma patologia num irmão, nascido posteriormente, por análise do sangue do cordão. Julgamos tratar-se do primeiro caso confirmado desta situação diagnosticada num doente em Portugal.

Novel FGFR1 Mutations in Kallmann Syndrome and Normosmic Idiopathic Hypogonadotropic Hypogonadism: Evidence for the Involvement of an Alternatively Spliced Isoform

OBJECTIVE: To determine the prevalence of fibroblast growth factor receptor 1 (FGFR1) mutations and their predicted functional consequences in patients with idiopathic hypogonadotropic hypogonadism (IHH). DESIGN: Cross-sectional study. SETTING: Multicentric. PATIENT(S): Fifty unrelated patients with IHH (21 with Kallmann syndrome and 29 with normosmic IHH). INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Patients were screened for mutations in FGFR1. The functional consequences of mutations were predicted by in silico structural and conservation analysis. RESULT(S): Heterozygous FGFR1 mutations were identified in six (12%) kindreds. These consisted of frameshift mutations (p.Pro33-Alafs*17 and p.Tyr654*) and missense mutations in the signal peptide (p.Trp4Cys), in the D1 extracellular domain (p.Ser96Cys) and in the cytoplasmic tyrosine kinase domain (p.Met719Val). A missense mutation was identified in the alternatively spliced exon 8A (p.Ala353Thr) that exclusively affects the D3 extracellular domain of FGFR1 isoform IIIb. Structure-based and sequence-based prediction methods and the absence of these variants in 200 normal controls were all consistent with a critical role for the mutations in the activity of the receptor. Oligogenic inheritance (FGFR1/CHD7/PROKR2) was found in one patient. CONCLUSION(S): Two FGFR1 isoforms, IIIb and IIIc, result from alternative splicing of exons 8A and 8B, respectively. Loss-of-function of isoform IIIc is a cause of IHH, whereas isoform IIIb is thought to be redundant. Ours is the first report of normosmic IHH associated with a mutation in the alternatively spliced exon 8A and suggests that this disorder can be caused by defects in either of the two alternatively spliced FGFR1 isoforms.