Clinical and radiological variants of the nail–patella syndrome: Why is it important to make a correct diagnosis?

BACKGROUND: Nail–patella syndrome is an autosomal dominant disease caused by LMX1B mutations, characterized by a combination of dermatological and musculoskeletal abnormalities. The classic tetrad of the nail–patella syndrome includes hypoplasia of the nail plates, absence or hypoplasia of the patella, elbow joint contractures, often accompanied by posterior subluxation of the radial head, presence of “iliac horns” on radiographs of the pelvic bones, and renal changes. However, its diagnosis and treatment are not described in sufficient detail in domestic and foreign literature.

AIM: This study aimed to analyze the variability of clinical and radiological manifestations in children with nail–patella syndrome.

MATERIALS AND METHODS: Nine patients with nail–patella syndrome were examined and treated (aged 4 months to 14 years). All children presented to the H. Turner National Medical Research Center for Children’s Orthopedics and Trauma Surgery with a diagnosis of congenital multiple arthrogryposis. The examination results excluded this diagnosis. The diagnosis of nail–patella syndrome has been verified.

RESULTS: Various variants of the nail–patella syndrome have been identified, with lesions to only the elbow joints (n = 3), damage to the upper and lower extremities (n = 5), and damage to only the lower extremities (n = 1). All patients had hypoplasia of fingernail plates. However, the pathognomonic sign – “iliac horns” on radiographs of the pelvic bones – was noted only in 33% of cases. Regarding functional disorders of the kidneys, proteinuria was observed in one patient, which appeared at the age of 15 years. In two cases, the parents suffered from this disease. A genetic examination was performed in three patients: a pathogenic variant in LMX1B was detected in a heterozygous state. All patients underwent conservative treatment for knee and elbow joint contractures and foot deformities. When casting, the presence of dislocation of the radial head or patella was considered. Surgical treatment was performed on five patients. The results of surgery on the lower extremities (knee contractures, foot deformities, and hip dislocation) were good in 87% of the cases. Recurrence of flexion contractures in the elbow joints was observed both after conservative and after surgical treatment in all cases; however, their severity varied.

CONCLUSIONS: Clinical observations were considered to attract the attention of doctors of different specialties to a rare pathology. Moreover, a molecular genetic study is recommended for the timely diagnosis of the nail–patella syndrome, determining the treatment techniques and disease prognosis.