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Polyglutamine expansions in the transcriptional co-repressor Atrophin-1, encoded by ATN1, cause the neurodegenerative condition dentatorubral-pallidoluysian atrophy (DRPLA) via a proposed novel toxic gain of function. We present detailed phenotypic information on eight unrelated individuals who have de novo missense and insertion variants within a conserved 16-amino-acid "HX repeat" motif of ATN1. Each of the affected individuals has severe cognitive impairment and hypotonia, a recognizable facial gestalt, and variable congenital anomalies. However, they lack the progressive symptoms typical of DRPLA neurodegeneration. To distinguish this subset of affected individuals from the DRPLA diagnosis, we suggest using the term CHEDDA (congenital hypotonia, epilepsy, developmental delay, digit abnormalities) to classify the condition. CHEDDA-related variants alter the particular structural features of the HX repeat motif, suggesting that CHEDDA results from perturbation of the structural and functional integrity of the HX repeat. We found several non-homologous human genes containing similar motifs of eight to 10 HX repeat sequences, including RERE, where disruptive variants in this motif have also been linked to a separate condition that causes neurocognitive and congenital anomalies. These findings suggest that perturbation of the HX motif might explain other Mendelian human conditions.

The purpose of this review is to describe neurological phenotypes associated with lysosomal storage diseases (LSDs), focusing on features arising from primary neuronal involvement. Clinical presentation, progression and genetic data, are discussed in detail in Part 2, the electronic material. Main features are summarized in Part 1. Insights gained from several observational studies are discussed. Prospective studies of the natural history of most neuronopathic LSDs have been hampered by the rarity of these conditions and the short survival of affected patients. Increasingly, longitudinal observations relating to neurological manifestations are being reported. Better clinical studies are necessary, including repeated measurements of disease progression to facilitate the development of sensitive scoring systems and appropriate counseling of affected individuals and their families. Ideally, clinical studies should involve a large cohort. As treatment becomes available, knowledge of disease expression and factors that influence the phenotype may enable critical assessment of therapeutic outcomes. It is hoped that increased familiarity with the clinical expression of individual LSDs will allow early diagnosis, so families at risk are given options to consider during future pregnancies. Early diagnosis also permits the introduction of timely intervention, to favoring improved outcome in cases that are potentially treatable.

X-linked adenoleukodystrophy is a genetic disease that affects the degradation of very long-chain fatty acids. In male patients, common pictures are the cerebral form (CALD), myeloneuropathy (AMN), and Addison-only. Objective: To describe the clinical course of affected male patients from South Brazil between 1993 and 2007. Methods: Affected male patients and their maternal lineages were studied from a clinical, neurological and biochemical standpoint. Results: Eighty-three male patients from 30 families were biochemically evaluated: 51 were affected. 27/51 (54%) presented the cerebral form; 11/51 had AMN (22%); 5 had Addison-only (10%), and 8 (16%) were asymptomatic. Between 2002 and 2006, the minimal incidence was 1:35,000 males in our State (South Brazil). Forty-three affected individuals were followed for 5.4 ± 3.7 years. Of 10 boys detected at early stages, three developed CALD. These three boys and another five CALD at baseline were referred to hematopoietic stem cell transplantation. Seven transplants were carried out, 5 with good clinical evolution after 2.2 years post-transplant. The non-transplanted case was later defined as a stable cerebral form. Discussion: Among the present families, the observed cases were comparable to the 50% expected by Mendelian segregation. Based on the natural history, the number of cases that developed CALD was similar to the expected. Transplants were successful in 70% of cases. The occurrence of a stable cerebral form pointed to an urgent need for better markers of active cerebral disease. 2009 Elsevier B.V. All rights reserved.