Israel Medical Association Journal

Nail-patella syndrome (NPS, OMIM: #161200), also known as Fong disease, hereditary osteo-onychodysplasia (HOOD), and Turner-Kieser syndrome, is a rare pleiotropic, multisystemic condition with an estimated incidence of 1 per 50,000. It is characterized mainly by developmental defects of dorsal limb structures due to symmetrical mesodermal and ectodermal abnormalities. It manifests as a classic clinical tetrad of distal digital abnormalities and fingernail dysplasia, which are typically bilateral and symmetrical, hypoplasia or absence of the patella, presence of iliac horns, and elbow deformities. It can also affect other structures (e.g., tendons, ligaments, and muscles), and may impact ophthalmic (glaucoma, increased ocular pressure and subsequent blindness), renal (nephropathy), neurological, orthopedic, and gastrointestinal systems. NPS can lead to sensorineural hearing loss and vasomotor problems [1,2]. Clinical manifestations vary greatly in frequency and severity. The prognosis is relatively good when clinical features are mild and cause no disability. However, serious and even life-threatening complications can occur. NPS is usually clinically diagnosed based on physical examination and radiological imaging. Genetic testing and renal biopsy can also assist in diagnosis confirmation.

Background: Nail-patella syndrome (NPS) is characterized by changes in the nails, knees, and elbows, as well as the presence of iliac horns detected by X-ray of the pelvis. A higher occurrence of psychiatric disorders has also been suggested in NPS. Heterozygous mutations in the gene encoding the LIM-homeodomain transcription factor (LMX1B) are identified in most patients with typical clinical findings of NPS.

Objective: To report on the association between NPS and schizophrenia.

Methods: Genomic DNA were isolated from a patient's venous blood and collected on ethylenediaminetetraacetic 5% with the Gentra Puregene Blood Kit. All exons and flanking regions of the LMX1B gene (LMX1B: NM_001174146.1) were amplified by standard polymerase chain reaction and analyzed by direct DNA sequencing with BigDye Terminators on an ABI 3100 sequencer. Sequence chromatograms were analyzed using SeqScape software version 1.1. Mutation analysis and characterization of variants was performed with the Alamut Software Version 2.1.

Results: We report a patient presenting to the psychiatry department with schizophrenia. Clinical examination revealed characteristic findings consistent with NPS. Since NPS was suspected, based on clinical findings, sequencing of all coding exons of LMX1B gene was completed. Results revealed a novel heterozygous mutation in the proband: c.546_547insACCG(het); p.Glu183Thrfs*11.

Conclusions: Based on LMX1B expression in brain regions that are implicated in neuropsychiatric illness, and especially in the development of dopaminergic neurons, we hypothesize that schizophrenia may be part of the clinical spectrum of NPS.