Familial cerebellar ataxia with hypogonadism

Ataxia, dementia, and hypogonadotropism caused by disordered ubiquitination

BACKGROUND

The combination of ataxia and hypogonadism was first described more than a century ago, but its genetic basis has remained elusive.

METHODS

We performed whole-exome sequencing in a patient with ataxia and hypogonadotropic hypogonadism, followed by targeted sequencing of candidate genes in similarly affected patients. Neurologic and reproductive endocrine phenotypes were characterized in detail. The effects of sequence variants and the presence of an epistatic interaction were tested in a zebrafish model.

RESULTS

Digenic homozygous mutations in RNF216 and OTUD4, which encode a ubiquitin E3 ligase and a deubiquitinase, respectively, were found in three affected siblings in a consanguineous family. Additional screening identified compound heterozygous truncating mutations in RNF216 in an unrelated patient and single heterozygous deleterious mutations in four other patients. Knockdown of rnf216 or otud4 in zebrafish embryos induced defects in the eye, optic tectum, and cerebellum; combinatorial suppression of both genes exacerbated these phenotypes, which were rescued by nonmutant, but not mutant, human RNF216 or OTUD4 messenger RNA. All patients had progressive ataxia and dementia. Neuronal loss was observed in cerebellar pathways and the hippocampus; surviving hippocampal neurons contained ubiquitin-immunoreactive intranuclear inclusions. Defects were detected at the hypothalamic and pituitary levels of the reproductive endocrine axis.

CONCLUSIONS

The syndrome of hypogonadotropic hypogonadism, ataxia, and dementia can be caused by inactivating mutations in RNF216 or by the combination of mutations in RNF216 and OTUD4. These findings link disordered ubiquitination to neurodegeneration and reproductive dysfunction and highlight the power of whole-exome sequencing in combination with functional studies to unveil genetic interactions that cause disease. (Funded by the National Institutes of Health and others.).

Hypogonadism and neurological diseases

Affected patients with hypogonadism have unnaturally low amounts of sex hormones that produce male and female sex characteristics. Males who suffer from this condition lack testosterone, while females fail to produce enough estrogen. Hypogonadism may be present at birth, or it may take effect years later following injury or illness to the sex glands. Hypogonadism has remarkable associations with variable medical disorders; however, it is characterized by a distinctive association with variable neurological disorders: such as epilepsy, ataxia, dysmyelination, nerve muscle disease, movement disorders, mental retardation and deafness. The remarkable neurological diseases with hypogonadism should not basically be regarded as coincidental findings, but possibly related to an intrinsic pathophysiological association.

Marinesco-Sjögren syndrome in a Bedouin family

Marinesco-Sjögren syndrome is rarely reported in the Middle East. This is the 2nd report of Marinesco-Sjögren syndrome in an Arab family. The clinical features of 2 affected brothers are described. Electrophysiological studies of the 2 patients showed primarily myopathic changes, whereas sural nerve biopsy revealed segmental demyelination and axonal degeneration. The role of tissue biopsy and the relationship to different electrophysiological studies are discussed. Both patients were noticed to have abnormally short lateral 3 metatarsals, a feature not present in other healthy members of the family. We suggest that this feature should be considered part of the syndrome profile.

Two sibs with chorioretinal dystrophy, hypogonadotrophic hypogonadism, and cerebellar ataxia: Boucher-Neuhäuser syndrome

We describe two sibs with chorioretinal dystrophy, hypogonadotrophic hypogonadism, and cerebellar ataxia, Boucher-Neuhäuser syndrome, a rare but distinct pleiotropic single gene disorder with an autosomal recessive pattern of inheritance. The cases presented illustrate that this syndrome is still poorly recognised. We provide a review and analysis of previously reported cases and the differential diagnosis, which might aid in the identification of additional cases.

Familial spinocerebellar ataxia and empty sella turcica

Pituitary anomaly associated with familial spinocerebellar ataxia (FSCA) is a rare occurrence. This is a report of a child with FSCA who had an empty sella turcica and growth hormone deficiency. Growth hormone therapy accelerated growth velocity and improved muscular strength. Endocrinopathy associated with FSCA is reviewed.

Cerebellar deficient folia (cdf): a new mutation on mouse chromosome 6

Cerebellar deficient folia, cdf, is a spontaneous autosomal recessive mutation in the mouse with unique pathology; the cerebellar cortex of the cdf/cdf mouse has only 7 folia instead of 10, which is the normal count for the C3H/HeJ strain in which this mutation arose. The cerebellum of the cdf/cdf mouse is hypoplastic and contains mineral deposits in the ventral vermis that are not present in controls. We used an intersubspecific intercross between C3H/HeSnJ-cdf/+ and Mus musculus castaneus (CAST/Ei) to map the cdf mutation to Chromosome (Chr) 6. The most likely gene order is D6Mit16-(cdf, D6Mit3)-D6Mit70-D6Mit29-D6Mit32, which positions cdf distal to lurcher (Lc) and proximal to motor neuron degeneration 2 (mnd2). The definitive visible phenotypes and histopathologies of cdf, Lc, and mnd2 support our mapping evidence that cdf is a distinct gene. The novel pathology of cdf should help elucidate the complicated process of cerebellar folia patterning and development. cdf recombined with mouse atonal homolog 1, Math1, the mouse homolog of the Drosophila atonal gene.

Cerebellar ataxia associated with hypogonadotropic hypogonadism and chorioretinopathy: a poorly recognized association

We report a male with cerebellar ataxia, hypogonadism and chorioretinopathy. The age of onset was 12. The parents were first cousins. Endocrinologic studies demonstrated hypogonadotropic hypogonadism due to pituitary dysfunction. The ocular disorder involved the choriocapillaris and the retina. The association may represent a separate syndrome, seldom recognized in the past.

Neurologic manifestations of hypothalamic disease

The hypothalamus, in addition to regulating the anterior and posterior pituitary, controls water balance through thirst, regulates food ingestion and body temperature, influences consciousness, sleep, emotion and other behaviors. Much has been learned of these effects in human disease through the clinical manifestations that occur with hypothalamic lesions. This study reviews the clinical pathologic correlations that have been made in recent years showing that regions of the hypothalamus exert functions in humans that are similar to those identified in experimental animals. Clinical pathologic correlations have not always provided precise analysis of hypothalamic function. The hypothalamus is small and often lesions that come to clinical attention achieve considerable size before their recognition, making local anatomic dissections of the effects of the lesions difficult. Nevertheless, the use of modern non-invasive techniques including CT scans and magnetic resonance imaging (MRI) have provided new information not previously available. This paper reviews several cases of hypothalamic disorder recognized recently. (1) A 33-year-old black man with hypothalamic sarcoidosis. Manifestations of hypothalamic dysfunction included panhypopituitarism, aggressive hyperphagia, polydipsia (partially due to hyperglycemia secondary to diabetes mellitus), drowsiness, depression, and irritability. (2) A 37-year-old woman with a large intrahypothalamic tumor (biopsy showed pituitary adenoma), with drowsiness, poikilothermia, lack of satiety, confusion, and memory loss. She becomes depressed when she is transiently more alert (as after hypertonic contrast-dye infusion). (3) A 60-year-old man with hypothalamic compression by a pituitary tumor, associated with syndrome of inappropriate ADH (SIADH), severe anorexia, memory loss, but preserved thirst. After surgical decompression of the tumor his appetite acutely recovered, but he developed severe hypo(poikilo)thermia. (4) A 45-year-old woman with a suprasellar craniopharyngioma presented with severe drowsiness, hyperphagia, depression, and memory loss post-operatively, which responded to antidepressants (except for the memory loss). She had extremely labile blood pressures and serum Na for about 1 week post-operatively.

Congenital cerebellar hypoplasia and hypogonadotropic hypogonadism

The association of cerebellar ataxia and non-neurological syndromes is a well known phenomenon. A 20-year-old male patient presented with a longstanding and non-progressive ataxia. Magnetic resonance examination revealed marked inferior vermian-cerebellar hypoplasia. He also showed a hypogonadism with low serum gonadotropin and prolactin levels. Chronic pulsatile gonadotropin-releasing hormone (GnRH) administration resulted in a small non-pulsatile luteinizing hormone (LH) increase and no follicle-stimulating hormone (FSH) elevation. This hormonal pattern suggests a primary deficiency of the gonadotroph and lactotroph cells, rather than a hypothalamic lesion. This is the first report where cerebellar hypoplasia of congenital origin is associated with hypogonadotropic hypogonadism. Because of consanguinity, autosomal recessive transmission is considered.

Neuronal ceroid lipofuscinosis with hypergonadotropic hypogonadism

A case of adolescent-onset neuronal ceroid lipofuscinosis presenting with chorea and evidencing pyramidal and cerebellar dysfunction as well as hypergonadotropic hypogonadism is reported. In this patient, primary ovarian failure may be due to accumulation of ceroid in the ovaries.

Familial spastic paraplegia with Kallmann's syndrome

A sibship is reported in which two males have spastic paraparesis and Kallmann's syndrome (hypogonadotrophic hypogonadism and anosmia). One of the brothers also is color blind. The association of familial spastic paraplegia and Kallmann's syndrome has not been described previously.

Familial cerebellar ataxia and hypogonadotropic hypogonadism: evidence for hypothalamic LHRH deficiency

A family with familial cerebellar ataxia and hypogonadotropic hypogonadism is described. The condition was inherited as an autosomal recessive defect. CT scan in one case revealed cerebellar and brain stem atrophy. Endocrinological tests showed abnormalities only in two patients who were clinically affected. In both cases raised gonadotropic levels were found after repetitive stimulation with luteining hormone-releasing hormone which suggests that the hypogonadism was due to a primary hypothalamic disturbance.