Malan syndrome is an ultrarare overgrowth-intellectual disability syndrome caused by NFIX variants, characterized by intellectual disability, postnatal overgrowth, and dysmorphic features. Seizures in Malan syndrome remain poorly understood. We surveyed caregivers of 53 individuals with Malan syndrome. Overall, 55% had seizures or electroencephalographic (EEG) abnormalities. Seizures occurred in 47%, with 28% experiencing drug-resistant epilepsy. The median age of seizure onset was 3 years. Epilepsy classifications included focal (40%) and unknown-onset tonic-clonic seizures (48%). Generalized tonic-clonic (8%), myoclonic (8%), and epileptic spasms (4%) were also reported. Of those with seizures, 44% had status epilepticus. Valproic acid was the most used antiseizure medication, with variable efficacy. This study represents the largest cohort to date, providing detailed descriptions of seizures in Malan syndrome, and lays a foundation for future research phenotyping epilepsy in affected individuals. Clinicians should maintain a high suspicion of seizures and monitor closely for status epilepticus in individuals with Malan syndrome.

Overgrowth-intellectual disability (OGID) syndromes encompass a group of rare neurodevelopmental disorders that frequently share common clinical presentations. Although the genetic causes of many OGID syndromes are now known, we lack a clear mechanistic understanding of how such variants disrupt developmental processes and ultimately culminate in overgrowth and neurological symptoms. Patient advocacy groups, such as the Overgrowth Syndromes Alliance (OSA), are mobilising patients, families, clinicians and researchers to work together towards a deeper understanding of the clinical needs of patients with OGID, as well as to understand the fundamental biology of the relevant genes, with the goal of developing treatments. In this Review, we summarise three OGID syndromes encompassed by the OSA, namely Sotos syndrome, Malan syndrome and Tatton-Brown-Rahman syndrome. We discuss similarities and differences in the biology behind each disorder and explore future approaches that could potentially provide a way to ameliorate some of the unmet clinical needs of patients with OGID.

Malan syndrome, an overgrowth disorder caused by pathogenic NFIX gene variants, is characterized by macrocephaly, distinct facial features, and intellectual disability. This case highlights the associated ophthalmologic features of this rare condition. We describe a young Spanish white man with progressive vision loss in the setting of a prior clinical diagnosis of Sotos syndrome, accompanied by developmental delay and epilepsy. Ophthalmic examination and imaging studies revealed visual acuity of 20/50 in each eye and bilateral optic atrophy. Genetic testing identified a heterozygous pathogenic NFIX variant, confirming Malan syndrome rather than NSD1-related Sotos syndrome. This case underscores the importance of genetic testing in patients with syndromic features, highlighting Malan syndrome as a differential diagnosis in cases of optic atrophy with overgrowth phenotypes.

Background/Objectives: Malan syndrome (MALNS) is an ultra-rare genetic disorder caused by aberrations in the NFIX gene, located at chromosome 19p13.2. Key features of MALNS include general overgrowth, a typical facial gestalt, muscle-skeletal abnormalities, speech difficulties and intellectual disability. Additionally, MALNS frequently presents with autism-like behaviour and social challenges. However, characterisation of the cognitive profile of MALNS, including social perception skills, is limited. Methods: Six children and adolescents with MALNS, whose clinical and emotional-behavioural features had been described in previous studies, were assessed by means of a single, co-normed neuropsychological battery covering multiple cognitive domains. Results: Consistent with their intellectual disability, performance was generally weak across all neuropsychological subtests. Nonetheless, memory for faces, visual attention and contextual (non-verbal) theory of mind emerged as relative strengths of the profile, both at group and individual levels. Conversely, tasks requiring verbal reasoning and language comprehension, such as comprehension of instructions and verbal theory of mind, represented weaknesses for all participants. Conclusions: These findings provide a further characterisation of cognitive and social functioning in MALNS, which can inform future research as well as clinical practice and rehabilitation.

Malan syndrome (MALNS), previously referred to as "Sotos syndrome 2" due to its resemblance to Sotos syndrome (SS), is an ultra-rare neurodevelopmental disorder characterized by overgrowth, typical craniofacial features, intellectual disability (ID), and a range of psychobehavioral, musculoskeletal, vision and neurological signs. As MALNS and SS partly overlap, it is essential to more accurately profile their clinical presentations and highlight their differences in order to improve syndrome specific management. An increasing number of individuals with MALNS reach adult-age though the natural history of the disorder is poorly characterized due to the small number of adult individuals described so far. As a consequence, current guidelines are limited to the pediatric population. Further delineation of MALNS is essential to optimize care in adulthood. A mixed approach based on cross-sectional data collection with a survey disseminated to caregivers of adults with molecularly confirmed MALNS and literature review was conducted. Twenty-eight caregivers completed the survey. Clinical presentation in adulthood is multisystemic and defined by psychobehavioral comorbidities (96%), musculoskeletal involvement (96%), vision impairment (96%) and neurological complications (86%). The most common signs were anxiety (79%), hypotonia (75%), movement difficulty (75%), scoliosis (64%), problems with coordination (61%), strabismus (57%), constipation (54%), breastbone abnormalities (54%) and advanced bone age during childhood (54%). Impaired vision was complicated by vision decline (36%) and optic atrophy (32%). We report some previously unidentified features, including high pain threshold (46%), incontinence (25%), tremors (21%), muscle hypoplasia (18%) and tics (18%). This survey in the adult population has allowed a more complete description of the natural history of MALNS. Our findings will contribute to the development and improvement of standards of care for adults with MALNS to assure optimal health monitoring and treatment of evolutive complications. We propose additional recommendations to the previous dataset of clinical evaluations specifically applied to adults. The comparison of MALNS and SS adult presentation highlights significant differences in terms of prevalence and severity of ID, behavioral issues, and vision problems, confirming that a proper differential diagnosis between the two conditions is indispensable to guide physicians and mental health professionals to syndrome specific management.