Brain dysplasia associated with Larsen-like syndrome

Subventricular glial nodules in neurofibromatosis 1 with craniofacial dysmorphism and occipital meningoencephalocele

BACKGROUND

Neurofibromatosis 1 (NF1) is autosomally inherited disorder, characterized by café au lait spots and multiple neurofibromas. Subventricular glial nodules (SVGN) are multiple gliosis bulging into the ventricular lumen, and histologically consist of astrocytes and their processes. Damage to ependymal cells induces SVGN formation.

CASE REPORT

This case report describes a 50-year-old man with NF1, craniofacial dysmorphism, including sphenoid dysplasia, bone defects at the middle posterior fossa, with disconnection of the parieto-occipital sutures, and the left orbital bone, and occipital meningoencephalocele. He died of status epileptics. Pathologically, many SVGN were found around the ventricular wall. Many ependymal cells were stripped during ventricular dilatation. Therefore, to prevent brain tissue insult from direct exposure to CSF, the proliferation of astrocytes and their processes was speculated to have substitute for ependymal cells and induced SVGN formation.

[Larsen-syndrome: final diagnosis following multiple surgical interventions]

Larsen-syndrome is a rare genetic skeletal dysplasia belonging to the group of actin-binding filamin B associated diseases. The features include congenital dislocations of the large joints, scoliosis and cervical kyphosis, short, broad, spatulate distal phalanges, and distinctive craniofacies. Diagnosis is based on clinical and radiographic findings and confirmed by molecular genetic testing. The authors have performed filamin B molecular genetic analysis since 2005 and have found several cases with unusual phenotypes since. This case report presents the diagnostic difficulties of a 30-year-old woman, who was operated several times with congenital hip dislocations and foot deformities. The craniofacial features, short, broad, spatulate fingers, scoliosis and cervical kyphosis directed diagnosis towards Larsen-syndrome and molecular genetic analysis confirmed a previously-described heterozygous missense mutation (c.G679A). They conclude that genetic analysis performed in time would prevent additional superfluous long diagnostic procedures in patients with rare diseases and would ensure adequate supportive therapy and management of the symptoms.

Larsen Syndrome

Larsen syndrome is a rare inherited disorder of collagen formation with multiple joint dislocations, cardiac abnormalities, short stature, talipes equinovarus, short and broad fingertips, spatula-like thumbs, supernumerary ossification center in the calcaneus, hearing loss, neurologic impairment, cryptorchidism, and characteristic craniofacial abnormalities. The sonographic prenatal findings in a case of Larsen syndrome at 26 weeks’ gestation, which demonstrated joint dislocations, hypertelorism, frontal bossing, micrognathia, and upper and lower limb shortening and confirmed at both 29 and 30 weeks’ gestation, are presented and discussed. When evaluating patients with a positive family history of Larsen syndrome, sonographers should carefully scan and meticulously assess the fetal extremities for signs of dislocation and the face for signs of flat features, hypertelorism, micrognathia, and depressed nasal bridge, distinctive features of the syndrome.

A molecular and clinical study of Larsen syndrome caused by mutations in FLNB

BACKGROUND

Larsen syndrome is an autosomal dominant osteochondrodysplasia characterised by large-joint dislocations and craniofacial anomalies. Recently, Larsen syndrome was shown to be caused by missense mutations or small inframe deletions in FLNB, encoding the cytoskeletal protein filamin B. To further delineate the molecular causes of Larsen syndrome, 20 probands with Larsen syndrome together with their affected relatives were evaluated for mutations in FLNB and their phenotypes studied.

METHODS

Probands were screened for mutations in FLNB using a combination of denaturing high-performance liquid chromatography, direct sequencing and restriction endonuclease digestion. Clinical and radiographical features of the patients were evaluated.

RESULTS AND DISCUSSION

The clinical signs most frequently associated with a FLNB mutation are the presence of supernumerary carpal and tarsal bones and short, broad, spatulate distal phalanges, particularly of the thumb. All individuals with Larsen syndrome-associated FLNB mutations are heterozygous for either missense or small inframe deletions. Three mutations are recurrent, with one mutation, 5071G-->A, observed in 6 of 20 subjects. The distribution of mutations within the FLNB gene is non-random, with clusters of mutations leading to substitutions in the actin-binding domain and filamin repeats 13-17 being the most common cause of Larsen syndrome. These findings collectively define autosomal dominant Larsen syndrome and demonstrate clustering of causative mutations in FLNB.

Morphometric studies of the entorhinal cortex in neuropsychiatric patients and controls: clusters of heterotopically displaced lamina II neurons are not indicative of schizophrenia

Subtle cytoarchitectural abnormalities of the rostral entorhinal cortex have been reported to be characteristic for schizophrenics. A main finding was the heterotopic displacement of clusters of lamina II neurons (which appeared morphologically immature) into layer III. Recent findings suggesting a considerable cytoarchitectural heterogeneity of the normal entorhinal cortex renewed interest in this problem and prompted the question of the extent to which 'aberrantly' located cell clusters are really disease-related. Being blind to the clinical diagnosis, we analyzed quantitatively the amount of entorhinal heterotopias in schizophrenics (n = 31), controls (n = 45) and depressive patients (n = 7). It was revealed that heterotopic cell clusters occurred in schizophrenics and controls with roughly the same frequency (amount of clusters per section). In depressive, there were significantly more heterotopias than in controls (right hemisphere). Our data show that heterotopias are common to the rostral part of the human entorhinal cortex and are not a suitable neuroanatomical marker of schizophrenia.

Neuronal heterotopias in the developing cerebral cortex produced by neurotrophin-4

The marginal zone (MZ) of embryonic neocortex is crucial to its normal development. We report that neurotrophin-4 (but not NT3 or NGF), applied to embryonic rodent cortex in vitro or in vivo, produces heterotopic accumulations of neurons in the MZ. Although heterotopia production is TrkB mediated, BDNF is >10-fold less effective than NT4. Heterotopic neurons have the same birth date and phenotype as normal MZ neurons; they are not the result of NT4-induced proliferation or rescue from apoptosis. We suggest that NT4 causes excess neurons to migrate into the MZ and thus may play a role in normal MZ formation as well as in the pathogenesis of certain human cortical dysplasias.