Familial mental retardation: a review and practical classification

Etiology of intellectual disability in individuals from special education schools in the south of Brazil

Background

Intellectual Disability (ID) is characterized by significant limitations that affect intellectual functioning, adaptive behavior, and practical skills which directly interfere with interpersonal relationships and the environment. In Western countries, individuals with ID are overrepresented in the health system, often due to associated comorbidities, and its life-time cost places ID as one of the most expensive conditions of all diagnoses in the International Classification of Diseases. Most of the people affected (75%) live in low-income countries, suffer from malnutrition, lack health care, and do not have access to adequate treatment. The aim of this study was to obtain an estimate of the diagnostic status as well as the prevalence of familial ID among individuals with serious (moderate or severe) ID in a region of the State of Santa Catarina, investigating attendees of special education schools of the Florianópolis Macroregion.

Methods

This was a cross-sectional study conducted between August 2011 and August 2014, through a semi-structured screening questionnaire for the collection of relevant developmental, clinical, familial and educational data, applied in an interview to guardians of students of special education schools of the macroregion of Florianópolis.

Results

The participant special schools enrolled close to 1700 students during the study period and the questionnaire was applied to 849 (50.5%). The male to female ratio of the participants was 1.39:1. Clear etiologic explanations were relatively scarce (24%); most diagnoses referring only to the type and the degree of impairment and for the majority (61.4%) the cause was unknown. About half were sporadic cases within their families (considering three generations). For 44.2% at least one other case of an ID-related condition in the extended family was mentioned, with 293 (34.5%) representing potential familial cases.

Conclusion

Here we describe the epidemiological profile, the available diagnostics, etiology, family history and possible parental consanguinity of participants with ID of special education schools in the South of Brazil. The main results show the need for etiological diagnosis and uncover the relevance of potential hereditary cases in a population where consanguineous unions have a relatively low frequency (0,6%) and highlight the need for public health actions.

Supplementary information

Supplementary information accompanies this paper at 10.1186/s12887-020-02382-5.

CNKSR1 gene defect can cause syndromic autosomal recessive intellectual disability

The advent of high-throughput sequencing technologies has led to an exponential increase in the identification of novel disease-causing genes in highly heterogeneous diseases. A novel frameshift mutation in CNKSR1 gene was detected by Next-Generation Sequencing (NGS) in an Iranian family with syndromic autosomal recessive intellectual disability (ARID). CNKSR1 encodes a connector enhancer of kinase suppressor of Ras 1, which acts as a scaffold component for receptor tyrosine kinase in mitogen-activated protein kinase (MAPK) cascades. CNKSR1 interacts with proteins which have already been shown to be associated with intellectual disability (ID) in the MAPK signaling pathway and promotes cell migration through RhoA-mediated c-Jun N-terminal kinase (JNK) activation. Lack of CNKSR1 transcripts and protein was observed in lymphoblastoid cells derived from affected patients using qRT-PCR and western blot analysis, respectively. Furthermore, RNAi-mediated knockdown of cnk, the CNKSR1 orthologue in Drosophila melanogaster brain, led to defects in eye and mushroom body (MB) structures. In conclusion, our findings support the possible role of CNKSR1 in brain development which can lead to cognitive impairment.

Bilateral anterior capsulotomy and amygdalotomy for mental retardation with psychiatric symptoms and aggression: A case report

RATIONALE

Mental retardation (MR) is a chronic condition that often has no readily identifiable cause or treatment. Aggression and psychiatric symptoms are prevalent in children with MR. Surgical treatment of aggression and psychiatric symptoms of MR is seldom investigated and studies are limited.

PATIENT CONCERNS

We encountered a 19-year-old female who had MR with aggression and psychiatric symptoms.

DIAGNOSES

She was diagnosed with mild MR with aggressiveness and psychiatric symptoms.

INTERVENTIONS

Because the patient was refractory to conservative treatment, bilateral anterior capsulotomy and amygdaloid neurosurgery were performed for her psychiatric symptoms and aggression. The benefits and side effects of the surgery were analyzed.

OUTCOMES

After surgery, the patient showed significant alleviation of her psychiatric symptoms and aggression with no observed side effects.

LESSONS

Bilateral anterior capsulotomy in combination with amygdaloid neurosurgery may resolve both psychiatric and aggressive symptoms. Future investigations of control studies with large patient cohorts are needed.