SPRED2 loss-of-function causes a recessive Noonan syndrome-like phenotype.

Upregulated signal flow through RAS and the mitogen-associated protein kinase (MAPK) cascade is the unifying mechanistic theme of the RASopathies, a family of disorders affecting development and growth. Pathogenic variants in more than 20 genes have been causally linked to RASopathies, the majority having a dominant role in promoting enhanced signaling. Here, we report that SPRED2 loss of function is causally linked to a recessive phenotype evocative of Noonan syndrome. Homozygosity for three different variants-c.187C>T (p.Arg63∗), c.299T>C (p.Leu100Pro), and c.1142_1143delTT (p.Leu381Hisfs∗95)-were identified in four subjects from three families. All variants severely affected protein stability, causing accelerated degradation, and variably perturbed SPRED2 functional behavior. When overexpressed in cells, all variants were unable to negatively modulate EGF-promoted RAF1, MEK, and ERK phosphorylation, and time-course experiments in primary fibroblasts (p.Leu100Pro and p.Leu381Hisfs∗95) documented an increased and prolonged activation of the MAPK cascade in response to EGF stimulation. Morpholino-mediated knockdown of spred2a and spred2b in zebrafish induced defects in convergence and extension cell movements indicating upregulated RAS-MAPK signaling, which were rescued by expressing wild-type SPRED2 but not the SPRED2Leu381Hisfs∗95 protein. The clinical phenotype of the four affected individuals included developmental delay, intellectual disability, cardiac defects, short stature, skeletal anomalies, and a typical facial gestalt as major features, without the occurrence of the distinctive skin signs characterizing Legius syndrome. These features, in part, characterize the phenotype of Spred2-/- mice. Our findings identify the second recessive form of Noonan syndrome and document pleiotropic consequences of SPRED2 loss of function in development.

Characteristics and etiologies of short stature in children: Experience of an endocrine clinic in a Tunisian tertiary care hospital.

BACKGROUND: Short stature is a common reason for referral to pediatric endocrinology clinics. It may be a manifestation of a pathological condition requiring early treatment. The aim of this study was to describe the characteristics and etiologies of short stature among children referred to the pediatric endocrinology clinic of the main pediatric tertiary care center in Tunisia. METHODS: Retrospective and descriptive study in the endocrinology unit of children referred for short stature between January 2012 and December 2016. Data on the patients' medical history, physical findings, laboratory tests, bone age and chromosomal analysis were collected. RESULTS: 470 children (266 males and 204 females) were referred during that period. 214 (45.5%) had normal height, and 80.8% of them were referred by general practitioners. The other 256 children (54.5%) had a confirmed short stature (mean age :7.2 years, mean height: -2.77 SDS). Endocrinological causes were the most common(43% GHD, 4% hypothyroidism) followed by intrauterine growth retardation IUGR (24%), genetic syndromes (8.4%), chronic pediatric diseases (7.8%), skeletal dysplasia (6.2%), normal variant of short stature (5%), and psychosocial deprivation (1.2%). Among non-endocrine causes, Turner syndrome was the most common genetic syndrome (4.4%), achondroplasia the main skeletal dysplasia (4%) and celiac disease the main chronic disease (3.4%). CONCLUSIONS: ST is largely overestimated in our country. Therefore, it is important to insist on adequate measurement and analysis of growth parameters to avoid unnecessary investigations. GHD and IUGR were the most common causes. Celiac disease, though frequent in Tunisia, is not a common cause of short stature.

Congenital hypothyroidism presenting with reversible renal impairment: an under-recognised problem?

BACKGROUND: Hypothyroidism with impairment of renal function and raised creatinine phosphokinase (CPK) is described in adults and children with acquired hypothyroidism, but not in congenital hypothyroidism. CASE PRESENTATION: A male infant born at term weighing 3390 g was seen aged 2 months with prolonged jaundice. Examination showed somnolence, umbilical hernia, enlarged fontanelles and lower limb edema; length 55 cm (-1.5 SD), weight 5.4 kg (-0.13 SD). Biochemistry showed fT4 < 1 pmol/L, TSH = 1044.36 µUI/mL, creatinine 77 µmol/L(normal <35 µmol/L), estimated glomerular filtration rate (GFR) 26 ml/min/1.73 m2, CPK 3952.5 IU/L (normal<400 IU/L). Ultrasound showed no thyroid tissue in the neck. In view of the renal impairment, peritoneal dialysis was initially contemplated but postponed and the child received levothyroxine 10 µg/kg/day. Two months later thyroid function tests, CPK and renal function had all normalized with creatinine 19 µmol/L and GFR 116 ml/min/1.73m2. DISCUSSION: Reversible renal impairment is attributable to severe congenital hypothyroidism causing decreased myocardial contractility and cardiac output and to a direct effect on the kidneys. Thyroid function should be checked in infants with renal impairment of unknown cause. Cautious fluid management is indicated in hypothyroid infants. Hypothyroidism may also be associated with elevated serum CPK levels but resolves with thyroxin therapy.

Central system nervous tuberculosis in infants.

The lack of specific symptoms and signs in patients with tuberculous meningitis makes early diagnosis difficult. In this report, we reviewed the clinical features and laboratory findings of 6 infants with central system nervous tuberculosis during a 10-year period. One of the patients had multifocal tuberculosis. The mean time to the diagnosis was 32 +/- 13.4 days. A contact source was identified in only 2 patients. All 6 patients had abnormal cerebrospinal fluid findings, less than 500 cells/microL with lymphocytic predominance. Computerized tomography (CT) and/or magnetic resonance imaging (MRI) revealed hydrocephalus with basal enhancement in 2 patients. One patient developed pontocerebellar and pituitary tuberculomas, which were responsible for compression and diabetes insipidus, 1 year after antituberculous treatment. These localizations are very rare. On the follow-up, 3 patients had hypoacousia and only 1 had severe sequelae, despite a diagnostic delay.