Spatial and spatiotemporal pattern analysis of coconut lethal yellowing in Mozambique

Coconut lethal yellowing (LY) is caused by a phytoplasma and is a major threat for coconut production throughout its growing area. Incidence of LY was monitored visually on every coconut tree in six fields in Mozambique for 34 months. Disease progress curves were plotted and average monthly disease incidence was estimated. Spatial patterns of disease incidence were analyzed at six assessment times. Aggregation was tested by the coefficient of spatial autocorrelation of the beta-binomial distribution of diseased trees in quadrats. The binary power law was used as an assessment of overdispersion across the six fields. Spatial autocorrelation between symptomatic trees was measured by the BB join count statistic based on the number of pairs of diseased trees separated by a specific distance and orientation, and tested using permutation methods. Aggregation of symptomatic trees was detected in every field in both cumulative and new cases. Spatiotemporal patterns were analyzed with two methods. The proximity of symptomatic trees at two assessment times was investigated using the spatiotemporal BB join count statistic based on the number of pairs of trees separated by a specific distance and orientation and exhibiting the first symptoms of LY at the two times. The semivariogram of times of appearance of LY was calculated to characterize how the lag between times of appearance of LY was related to the distance between symptomatic trees. Both statistics were tested using permutation methods. A tendency for new cases to appear in the proximity of previously diseased trees and a spatially structured pattern of times of appearance of LY within clusters of diseased trees were detected, suggesting secondary spread of the disease.

Simultaneous supratentorial and brainstem abscesses due to Listeria monocytogenes

Multiple supratentorial abscesses caused by Listeria monocytogenes are rare. We report the simultaneous occurrence of multiple supratentorial and brainstem abscesses due to Listeria, in a patient under corticotherapy for an exacerbation of ulcerative colitis. MR imaging features before and after successful conservative treatments are depicted. In immunocompromised patients with supratentorial listerial abscesses, the coexistence of brainstem abscedation is exceptional. Despite high mortality associated with listerial abscesses, this case illustrates the possibility of a good clinical outcome, if the appropriate antibiotic regimen is instituted and the immunosuppressant agent is discontinued.

Clinical heterogeneity of autosomal recessive spastic paraplegias: analysis of 106 patients in 46 families

BACKGROUND

Hereditary spastic paraplegias (HSPs) are a heterogeneous group of neurodegenerative disorders characterized by progressive and predominant spasticity of the lower limbs, in which dominant, recessive, and X-linked forms have been described. While autosomal dominant HSP has been extensively studied, autosomal recessive HSP is less well known and is considered a rare condition.

OBJECTIVE

To analyze the clinical presentation in a large group of patients with autosomal recessive HSP from Portugal and Algeria to define homogeneous groups that could serve as a guide for future molecular studies.

RESULTS

Clinical features in 106 patients belonging to 46 Portuguese and Algerian families with autosomal recessive HSP are presented, as well as the results of molecular studies in 23 of these families. Five phenotypes are defined: (1) pure early-onset families, (2) pure lateonset families, (3) complex families with mental retardation, (4) complex families with mental retardation and peripheral neuropathy, and (5) complex families with cerebellar ataxia. Six additional families have specific complex presentations, each of which is unique in the present series. Pyramidal signs in the upper limbs and pes cavus are frequent findings, while pseudobulbar signs, including dysarthria, dysphagia, and brisk jaw jerks, are more frequent in the complex forms. The complex forms have a poorer prognosis, while pure forms, particularly those with early onset, are more benign. One Algerian pure early-onset kindred was linked to the locus on chromosome 8, previously reported in 4 Tunisian families. Two of the Portuguese kindreds with complex forms (one with mental retardation and the other associated with hypoplasia of the corpus callosum) showed linkage to the locus recently identified on chromosome 16.

CONCLUSIONS

Although autosomal recessive HSP represents a heterogeneous group of diseases, some phenotypes can be defined by analyzing a large group of patients. The fact that only one Algerian family was linked to chromosome 8 suggests that this is a rare localization even in kindreds with the same ethnic background. Linkage to chromosome 16 was found in 2 clinically diverse Portuguese kindreds, illustrating that this locus is also rare and may correspond to different phenotypes.

A study of 159 Portuguese patients with familial amyloidotic polyneuropathy (FAP) whose parents were both unaffected

We reviewed 1233 cases of familial amyloidotic polyneuropathy (FAP) from 489 Portuguese families registered at the Centro de Estudos de Paramiloidose, Porto, Portugal. It was found that in 159 cases, neither parent had shown symptoms of this hereditary dominant form of peripheral neuropathy. These cases appear to form a distinct group, with a later age at onset (mean 45.1 years, SD 12.0) than the group of patients with one affected parent (mean 31.2 years, SD 6.9) and a geographical origin not quite in the areas where the disease is most prevalent. Though this group is not significantly different from the general group of patients in clinical presentation at onset and severity of the disease, the average interval between onset and diagnosis (mean 4.5 years, SD 3.2) reflects the difficulties in diagnosing these patients in the absence of a positive family history. From the analysis of pedigrees and in spite of a large number of isolated cases, the occurrence of new mutations could not be proven, and it seems more likely that, in some families, the FAP gene may result in a milder expression or even remain "silent" for several generations. Further investigation of this discrepancy may prove to be important in elucidating the mechanisms involved in the pathogenetic process.