Misclassification in defining and diagnosing microcephaly.

BACKGROUND: Several health agencies define microcephaly for surveillance purposes using a single criterion, a percentile or Z-score cut-off for newborn head circumference. This definition, however, conflicts with the reported prevalence of microcephaly even in populations with endemic Zika virus. OBJECTIVE: We explored possible reasons for this conflict, hypothesising that the definition of microcephaly used in some studies may be incompletely described, lacking the additional clinical criteria that clinicians use to make a formal diagnosis. We also explored the potential for misclassification that can result from differences in these definitions, especially when applying a percentile cut-off definition in the presence of the much lower observed prevalence estimates that we believe to be valid. METHODS: We conducted simulations under a theoretical bimodal distribution of head circumference. For different definitions of microcephaly, we calculated the sensitivity and specificity using varying cut-offs of head circumference. We then calculated and plotted the positive predictive value for each of these definitions by prevalence of microcephaly. RESULTS: Simple simulations suggest that if the true prevalence of microcephaly is approximately what is reported in peer-reviewed literature, then relying on cut-off-based definitions may lead to very poor positive predictive value under realistic conditions. CONCLUSIONS: While a simple head circumference criterion may be used in practice as a screening or surveillance tool, the definition lacks clarification as to what constitutes true pathological microcephaly and may lead to confusion about the true prevalence of microcephaly in Zika-endemic areas, as well as bias in aetiologic studies.

[Microcephaly]. / Microcefalia.

Microcephaly is defined as a head circumference more than two standard deviations below the mean for gender and age. It is an important neurological sign and predictor of future disability. One of its diagnostic difficulties lies in the ranks of the head circumference reference against which we measure each child. The WHO developed growth curves that could be used universally, topic on which there may be discrepancies. Recently, Zika virus epidemic demanded to review the criteria for the diagnosis of microcephaly. The classification of the microcephaly in congenital and postnatal makes it possible to define the etiology, the associated symptoms and the prognosis. The evaluation of a child with microcephaly requires a thorough analysis of its history, clinical examination and complementary studies. MRI is the first step in the etiologic research. Genetic causes forming part of a syndrome or not, and prenatal infections are the most frequent etiologies but in half of the cases, no cause is found. The comparative hybridization genomic array (array-CGH) and full exome sequencing are techniques that more and more help us in the evaluation of patients with microcephaly. Depending on the cause and severity, children with microcephaly may have different problems such as intellectual disabilities, development retardation, epilepsy, cerebral palsy, as well as vision and hearing disorders. The microcephaly requires a multidisciplinary approach both in its initial assessment as it is its post-program monitoring.

Microcefalia / Microcephaly

La microcefalia se define como un perímetro cefálico de más de dos desviaciones estándar por debajo de la media para edad y sexo. Es un importante signo neurológico y predictor de discapacidad futura. Una de las dificultades de su diagnóstico radica en los rangos de referencia del perímetro cefálico contra la que medimos a cada niño. La OMS elaboró curvas de crecimiento del perímetro cefálico que podrían ser utilizadas en forma universal, tema sobre el que puede haber discrepancias. La epidemia por virus del Zika exigió revisar recientemente los criterios del diagnóstico de microcefalia. La clasificación de la microcefalia en congénita y postnatal posibilita definir la etiología, los síntomas asociados y el pronóstico. La evaluación de un niño con microcefalia requiere un exhaustivo análisis de sus antecedentes, examen clínico y estudios complementarios. La resonancia magnética es el primer escalón en la investigación etiológica. Las causas genéticas formando parte o no de cuadros sindrómicos y las infecciones intraútero, son las etiologías más frecuentes, pero en la mitad de los casos no se encuentra una causa. La hibridación comparativa matriz genómica (array-CGH) y la secuenciación del exoma completo son técnicas que cada vez más ayudan en la evaluación de pacientes con microcefalia. Dependiendo de la causa y la gravedad, los niños con microcefalia pueden tener diferentes problemas como discapacidad intelectual, retraso del desarrollo, epilepsia, parálisis cerebral, así como trastornos oftalmológicos y auditivos. La microcefalia exige un enfoque multidisciplinario tanto en su evaluación inicial como es su seguimiento posterior.

Microcephaly is defined as a head circumference more than two standard deviations below the mean for gender and age. It is an important neurological sign and predictor of future disability. One of its diagnostic difficulties lies in the ranks of the head circumference reference against which we measure each child. The WHO developed growth curves that could be used universally, topic on which there may be discrepancies. Recently, Zika virus epidemic demanded to review the criteria for the diagnosis of microcephaly. The classification of the microcephaly in congenital and postnatal makes it possible to define the etiology, the associated symptoms and the prognosis. The evaluation of a child with microcephaly requires a thorough analysis of its history, clinical examination and complementary studies. MRI is the first step in the etiologic research. Genetic causes forming part of a syndrome or not, and prenatal infections are the most frequent etiologies but in half of the cases, no cause is found. The comparative hybridization genomic array (array-CGH) and full exome sequencing are techniques that more and more help us in the evaluation of patients with microcephaly. Depending on the cause and severity, children with microcephaly may have different problems such as intellectual disabilities, development retardation, epilepsy, cerebral palsy, as well as vision and hearing disorders. The microcephaly requires a multidisciplinary approach both in its initial assessment as it is its post-program monitoring.

D40/KNL1/CASC5 and autosomal recessive primary microcephaly.

Autosomal recessive primary microcephaly (MCPH) is a very rare neuro-developmental disease with brain size reduction. More than a dozen loci encoding proteins of diverse function have been shown to be responsible for MCPH1-13. Mutations in the D40/KNL1/CASC5 gene, which was initially characterized as a gene involved in chromosomal translocation in leukemia and as a member of the cancer/testis gene family, was later found to encode a kinetochore protein essential for mitotic cell division and to cause MCPH4. Although our previous studies showed that this gene is required for cell growth and division in vitro and in animal experiments, the revelation that mutations in this gene caused microcephaly provides in vivo evidence of a critical role in brain growth. In this review, we describe mutated gene targets responsible for MCPH1-13 and summarize clinical studies of, and molecular and biological aspects of the gene and encoded protein responsible for MCPH4.

Resuming the obsolete term "small head": when microcephaly occurs without cognitive impairment.

Microcephaly is defined as a head circumference measurement of 2 or 3 standard deviations below the mean for age and sex. However, distinguishing the value of -2 or -3 standard deviations as a cutoff is relevant in the clinical practice, since the limit of -3 standard deviations is more frequently associated with cognitive impairment. The use of ultrasound scans in pregnancy has allowed the identification of subjects with a measurement of the head circumference at the limit of the cutoff for gestational age, but who do not subsequently show cognitive delay. The same is true for newborns with a -2 to -3 standard deviations cutoff, and without anomalous clinical signs, for which a cognitive delay is not easily diagnosed. In this case, to define an infant as being affected by microcephaly (with a prognosis usually recognized as harmful) may be unnecessarily distressful for parents or caregivers. In the cases mentioned, resuming the word "small head" instead of microcephaly to define such subjects could be more appropriate and more appreciated.

Novel VPS13B Mutations in Three Large Pakistani Cohen Syndrome Families Suggests a Baloch Variant with Autistic-Like Features.

BACKGROUND: Cohen Syndrome (COH1) is a rare autosomal recessive disorder, principally identified by ocular, neural and muscular deficits. We identified three large consanguineous Pakistani families with intellectual disability and in some cases with autistic traits. METHODS: Clinical assessments were performed in order to allow comparison of clinical features with other VPS13B mutations. Homozygosity mapping followed by whole exome sequencing and Sanger sequencing strategies were used to identify disease-related mutations. RESULTS: We identified two novel homozygous deletion mutations in VPS13B, firstly a 1 bp deletion, NM_017890.4:c.6879delT; p.Phe2293Leufs*24, and secondly a deletion of exons 37-40, which co-segregate with affected status. In addition to COH1-related traits, autistic features were reported in a number of family members, contrasting with the "friendly" demeanour often associated with COH1. The c.6879delT mutation is present in two families from different regions of the country, but both from the Baloch sub-ethnic group, and with a shared haplotype, indicating a founder effect among the Baloch population. CONCLUSION: We suspect that the c.6879delT mutation may be a common cause of COH1 and similar phenotypes among the Baloch population. Additionally, most of the individuals with the c.6879delT mutation in these two families also present with autistic like traits, and suggests that this variant may lead to a distinct autistic-like COH1 subgroup.

Expanding the clinical and mutational spectrum of Kaufman oculocerebrofacial syndrome with biallelic UBE3B mutations.

Biallelic mutations of UBE3B have recently been shown to cause Kaufman oculocerebrofacial syndrome (also reported as blepharophimosis-ptosis-intellectual disability syndrome), an autosomal recessive condition characterized by hypotonia, developmental delay, intellectual disability, congenital anomalies, characteristic facial dysmorphic features, and low cholesterol levels. To date, six patients with either missense mutations affecting the UBE3B HECT domain or truncating mutations have been described. Here, we report on the identification of homozygous or compound heterozygous UBE3B mutations in six additional patients from five unrelated families using either targeted UBE3B sequencing in individuals with suggestive facial dysmorphic features, or exome sequencing. Our results expand the clinical and mutational spectrum of the UBE3B-related disorder in several ways. First, we have identified UBE3B mutations in individuals who previously received distinct clinical diagnoses: two sibs with Toriello-Carey syndrome as well as the patient reported to have a "new" syndrome by Buntinx and Majewski in 1990. Second, we describe the adult phenotype and clinical variability of the syndrome. Third, we report on the first instance of homozygous missense alterations outside the HECT domain of UBE3B, observed in a patient with mildly dysmorphic facial features. We conclude that UBE3B mutations cause a clinically recognizable and possibly underdiagnosed syndrome characterized by distinct craniofacial features, hypotonia, failure to thrive, eye abnormalities, other congenital malformations, low cholesterol levels, and severe intellectual disability. We review the UBE3B-associated phenotypes, including forms that can mimick Toriello-Carey syndrome, and suggest the single designation "Kaufman oculocerebrofacial syndrome".

Microcephaly with simplified gyral pattern: MRI classification.

OBJECTIVES: To develop subjective (visual) and objective (morphometric) rating scales for the classification of MRI in infants who had microcephaly with a simplified gyral pattern (MSGP) and to validate the first by the latter. METHODS: We compared the MRI of 12 patients with MSGP and of 5 term-born control infants. Visual rating and morphometric analysis was performed for gyration and associated brain abnormalities of basal ganglia, lateral ventricles, pons, cerebellum, and corpus callosum. RESULTS: Gyral pattern was rated reliably as normal in the control infants, simplified in 6 patients, and severely simplified in the other 6 patients. Associated brain abnormalities were reported in 10 of 12 patients. Visual rating correlated well with the morphometric measures. CONCLUSIONS: Our visual rating scale for a simplified gyral pattern proved to be sensitive and reliable. Associated brain abnormalities are frequent, which underlines the need for a consistent scoring in these patients.

Microcephaly associated with abnormal gyral pattern.

Primary microcephaly is a heterogeneous group of cerebral malformations either with a relatively well-preserved or an abnormal gyral pattern. We describe the MRI findings and clinical features of 14 children with the combination of microcephaly and an abnormal gyral pattern. All children except one were Arabs and nine out of the 14 patients were born to consanguineous parents. Seven patients showed features of a simplified gyral pattern with relatively preserved posterior fossa structures. Two boys had a cortical malformation in the agyria-pachygyria spectrum; one of these two patients showed agenesis of the corpus callosum and severe cerebellar hypoplasia as well. The microcephaly was associated with polymicrogyria and leukoencephalopathy in two patients, with cortical dysplasia and hypogenesis of the corpus callosum in one patient, with agyria-pachygyria with callosal and pontocerebellar dysplasia in one patient, and a simplified gyral pattern with severe cerebellar hypoplasia in one case. One patient died in the neonatal period and three in infancy. All patients, who survived the neonatal period, had developmental delay, intellectual disability, and neurological deficits, and nine suffered from epilepsy.

Autopsy case of microcephalic osteodysplastic primordial "dwarfism" type II.

Microcephalic osteodysplastic primordial "dwarfism" (MOPD) is a group of disorders similar to Seckel syndrome. Three subtypes (types I-III) have been reported. We report here the first autopsy case of MOPD type II. The patient was a Japanese girl with typical clinical and radiological manifestations of MOPD type II. The manifestations included severe intrauterine and postnatal growth failure, microcephaly, a distinctive facial appearance, micromelia, brachytelephalangy, coxa vara, and V-shaped metaphyses of the distal femora. Other than small cerebral hemispheres, no neuropathological abnormalities were found. Chondro-osseous histology showed thinning of the growth plate, ballooned chondrocytes, reduced cellularity, lack of zonal and columnar formations, and poor formation of primary trabeculae. These findings suggest that impairment of chondrocytic formation and differentiation is the major pathogenesis of MOPD type II.

Association of epilepsy with different groups of microcephaly.

Sixty-six participants (33 males, 33 females) with microcephaly (MC), age range from 2 to 19 years old, were evaluated. MC was classified pathogenetically into isolated MC (IMC) and multiple MC (MMC) and classified etiologically into primary MC (PMC) and secondary MC (SMC). Both IMC and MMC were further classified. Overall prevalence of epilepsy was 40.9%. Furthermore, there was a significantly higher prevalence of epilepsy in males. Main seizure type was generalized tonic-clonic seizures. Generally, learning disability (LD) was diagnosed in 93.9% and profound LD was evident in 43.9% of participants. There was an inverse correlation between severity of epilepsy and IQ but a positive correlation between severity of epilepsy and degree of LD. Differences in the success rate between monotherapy and polytherapy or response to antiepileptic drugs were not observed. Results suggest that epilepsy may be associated with the lower cognitive ability of the participants with microcephaly. The pathogenetic classification proposed is of value in delineating the prevalence of epilepsy and LD in the different varieties of MC as compared with the etiological classification.

[Type II primordial microcephalic dwarfism. Report of a patient with completed growth]. / Nanisme microcéphalique primordial de type II. A propos d'un cas ayant terminé sa croissance.

Type II primordial microcephalic dwarfism is a rare form of bird-headed dwarfism individualized in 1982 by Majewski. A case in a female patent with completed growth illustrates the main features, which include severe growth retardation (greater than 4 SD reduction in height) of prenatal onset, short limbs, coxa vara with epiphysiolysis of the hips, metaphyseal flaring and, in some instances, shortness of the ulnas and curvature of the radiuses. A genetic cause (with autosomal recessive inheritance) is very likely. A number of features in the case reported herein may be of pathogenetic relevance: growth hormone levels were elevated before closure of the epiphyses and normal thereafter, no growth spurt occurred at puberty, polycystic ovaries with hirsutism developed after puberty, and surgical wound healing was unusually slow.

An apparently new mental retardation syndrome in three elderly sisters.

Three elderly sisters with profound mental retardation in association with the clinical features of microcephaly, short stature, brachydactyly type D, flattened occiput, down-slanting palpebral fissures, low-set large ears, broad prominent nose and kyphoscoliosis have been investigated. Each was more than 60 years of age and their clinical features were strikingly similar. The disorder has several manifestations in common with Rubenstein-Taybi syndrome and appears to be inherited as an autosomal recessive in this family.