A 46-year-old male patient, with a known history of human immunodeficiency virus and hepatitis C virus coinfection, underwent a computed tomography (CT) to assess liver lesions detected by US, which were later identified as haemangiomas. On physical examination, hypoplastic fingernails were found.
Incidentally, the CT revealed the presence of bilateral osseous processes projecting from the posterior aspect of the iliac bones (Figures 1a and 1b). Anteroposterior and lateral knee radiographs showed bilateral patellar hypoplasia associated with luxation (Figure 2a), while elbow radiographs demonstrated bilateral radial head hypoplasia with radio-humeral dislocation and abnormal radial curvature (Figure 2b).
Background
Nail–patella syndrome (NPS), also known as Fong disease, is a rare hereditary autosomal dominant disorder caused by LMX1B mutations producing a loss of function of the LMX1B protein. NPS is characterised by a classic tetrad: hypoplastic or absent fingernails, hypoplastic or absent patellae, bilateral iliac prominences (iliac horns), and elbow deformities [1–4]. Iliac horns are pathognomonic for this syndrome [1,2] but are not universally present, occurring in approximately 70–80% of cases [2]. They are bilateral prominences growing from the posterior iliac surfaces, frequently palpable, and named after the bony prominences on the heads of horned animals. Other disorders, such as nephropathy and glaucoma, are associated [1], but renal involvement is the major determinant of the prognosis for NPS [4]. Molecular tests can identify LMX1B gene mutations helping to confirm NPS diagnosis.
Clinical Perspective
Patients with NPS usually present nonspecific symptoms related to skeletal abnormalities. Cases can range from mild with no functional impact to severe, leading to disability. Our patient presented hypoplastic fingernails and limited supination of the elbows, as well as occasional mild episodes of patellar subluxation. The combined radiological and clinical findings confirmed the diagnosis of NPS. Given the patient’s age, minimal functional limitations, and adaptive behaviours, no immediate intervention was necessary.
Imaging Perspective
Being typically a syndrome diagnosed incidentally in radiological tests, radiological findings are typical in both conventional radiographs and CT, with the presence of bilateral iliac horns being pathognomonic for this syndrome. Other radiological signs are patellar hypoplasia and hypoplasia of the radial head with associated radio-humeral dislocation. All these findings were observed in our patient. Absence or hypoplasia of the fibula and asymmetric growth of the femoral condyles may also be present.
Outcome
In this case we present characteristic radiological findings of a rare syndrome that allow a precise diagnosis to be made without the need to perform further complementary tests.
Treatment of skeletal abnormalities is usually not necessary as symptoms are usually mild.
Nephropathy is the most important associated clinical alteration and determines the prognosis of NPS, being necessary a strict follow-up of the disease due to the possibility of kidney failure.
Take Home Message / Teaching Points
The characteristic radiological findings allow a diagnosis of nail–patella syndrome to be established. Knowledge of this syndrome is key to detecting associated clinical alterations such as nephropathy and glaucoma.
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Nail–patella syndrome
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Based on the provided CT and X-ray images, the following prominent features can be observed:
These imaging findings, in conjunction with the clinical examination, strongly suggest the classic presentation of NPS.
Considering the patient’s imaging and clinical features (bilateral iliac horns, dysplastic patellae and nails, abnormal elbow joint morphology), as well as literature references and the hallmark traits of this syndrome, a diagnosis of Nail–Patella Syndrome (NPS) can be confirmed.
Although the patient also has HIV and hepatitis C (HCV), these comorbidities do not alter the principal clinical diagnosis and radiological findings of NPS. They should, however, be addressed and managed separately during follow-up.
1. Treatment Strategies
2. Rehabilitation / Exercise Prescription Recommendations
Given that the patient’s overall mobility remains relatively good, with only mild limitations in joint flexibility and light discomfort, it is suggested to focus on improving joint range of motion and muscle strength, adhering to the FITT-VP principle with a gradual progression:
During training, close attention should be paid to the stability of the knee and elbow joints. If joint pain or swelling occurs, reevaluation is recommended, and adjustments to decrease the intensity or temporarily halt the exercises may be necessary.
Special Note: Regularly monitor renal function to detect any potential NPS-related renal complications. Comorbid conditions (e.g., HIV, HCV) should be concurrently managed by specialized healthcare providers.
Disclaimer: This report is based on the available information for reference and does not replace in-person consultations or professional medical advice. Specific diagnoses and treatment plans should be determined by considering the patient's actual condition and proper consultation with relevant specialists.
Nail–patella syndrome
