Neurocutaneous syndrome with mental delay, autism, blockage in intracellular vescicular trafficking and melanosome defects

Autism spectrum disorders: the quest for genetic syndromes

Autism spectrum disorders (ASD) are a heterogeneous group of neurodevelopmental disabilities with various etiologies, but with a heritability estimate of more than 90%. Although the strong correlation between autism and genetic factors has been long established, the exact genetic background of ASD remains unclear. A number of genetic syndromes manifest ASD at higher than expected frequencies compared to the general population. These syndromes account for more than 10% of all ASD cases and include tuberous sclerosis, fragile X, Down, neurofibromatosis, Angelman, Prader-Willi, Williams, Duchenne, etc. Clinicians are increasingly required to recognize genetic disorders in individuals with ASD, in terms of providing proper care and prognosis to the patient, as well as genetic counseling to the family. Vice versa, it is equally essential to identify ASD in patients with genetic syndromes, in order to ensure correct management and appropriate educational placement. During investigation of genetic syndromes, a number of issues emerge: impact of intellectual disability in ASD diagnoses, identification of autistic subphenotypes and differences from idiopathic autism, validity of assessment tools designed for idiopathic autism, possible mechanisms for the association with ASD, etc. Findings from the study of genetic syndromes are incorporated into the ongoing research on autism etiology and pathogenesis; different syndromes converge upon common biological backgrounds (such as disrupted molecular pathways and brain circuitries), which probably account for their comorbidity with autism. This review paper critically examines the prevalence and characteristics of the main genetic syndromes, as well as the possible mechanisms for their association with ASD.

New neurocutaneous syndrome with defect in cell trafficking and melanosome pathway: the future challenge

OBJECTIVE

Case study of a CNS impairment lacking in presumptive cause; case presents with a clinical phenotype encompassing multiple differently expressed and combined symptoms, as well as a subtle skin defect.

MATERIALS AND METHODS

A 6-year-old male with apparently isolated mental delay, speech delay, attention deficit/hyperactivity disorder, epilepsy, and subtle and insignificant skin dyschromias. The patient underwent a systematic evaluation, including clinical history; medical, neurological and ophthalmologic examinations. Skin, teeth, nails, hair and sudation were examined for defects. Routine laboratory tests for blood, urine, were performed. The proband had thyroid function tests, electrocardiography, genitourinary system and abdominal examinations. Special examinations pertaining to mental performance, biochemistry, chromosome studies, imaging and electrodiagnostic studies, and skin biopsy were also performed.

RESULTS

Investigators ruled out genetic syndromes, congenital infections, fetal deprivation, perinatal insults, intrauterine exposure to drug abuse, and postnatal events such as CNS infections as possible common causes of brain impairment. Being all further test negative, the patient exhibited an ultrastructural defect of the skin, identical to that previously described [Buoni S, Zannolli R, de Santi MM, Macucci F, Hayek J, Orsi A et al. Neurocutaneous syndrome with mental delay, autism, blockage in intracellular vesicular trafficking and melanosome defects. Eur J Neurol 2006;13:842-51], suggesting that some cell compartments, such as rough endoplasmic reticulum, lysosomes, Golgi apparatus, and the vesicular zone (racket) of Birbeck granules, sharing similar components, can be altered, resulting in a common defect in cell trafficking, associated to melanosome defects.

CONCLUSIONS

This new devasting, ultrastructural phenotype accompanied by apparently unspecific and mixed neurological symptoms should represent a future challenge to finally discover the pathogenesis of many childhood CNS symptoms, that currently seem to lack any apparent cause.