Angel-Shaped Phalango-Epiphyseal Dysplasia

A form of acromelic dysplasia characterized by the distinctive radiological sign of angel-shaped middle phalanges, a typical metacarpophalangeal pattern profile (mainly affecting first metacarpals and middle phalanges of second, third and fifth digits, which all appear short), epiphyseal changes in the hips and, in some, abnormal dentition and delayed bone age.

Epidemiology

The prevalence is unknown. ASPED is a rare disease with less than 20 cases reported in the literature to date, however, it is likely underdiagnosed.

Clinical description

Clinical manifestations in ASPED are not only restricted to the hands, and the original description reported various combinations of angel-shaped middle phalanges, hip dysplasia and dental anomalies (hypodontia). Patient stature ranges from short to normal. Hip dysplasia gives rise to premature or severe osteoarthritis causing severe intermittent hip pain. Non-specific brachydactyly and hyperextensible interphalangeal joints have been reported, as well as delayed bone age. Delayed dentition, abnormally placed teeth, premature loss of teeth, abnormal enamel, and malocclusion have also been described in some.

Etiology

ASPED is caused by mutations in the growth differentiation factor 5 (GDF5) gene, located on chromosome 20q11.2, encoding CDMP1 (cartilage derived morphogenetic protein). CDMP1 belongs to the TGF beta super family and plays a role in bone growth and joint morphogenesis.

Diagnostic methods

Diagnostic methods include skeletal x-rays, showing the typical radiological features of ASPED, along with GDF5 molecular analysis, which confirms diagnosis. Angel-shaped middle phalanges are usually an isolated bone anomaly, and are shaped like ''Christmas tree angels'', with the wings formed by the diaphyseal cuff of bone surrounding the phalanx, the skirt by a cone-shaped epiphysis, and the head by the distal pseudoepiphysis. Angel-shaped phalanges can be difficult to find in adults. However, they can be associated with dental anomalies, hip dysplasia and short stature.

Differential diagnosis

The main clinical differential diagnosis is Brachydactyly type C (see this term), which is also associated with a GDF5 mutation, suggesting that both syndromes may be part of the same clinical spectrum.

Antenatal diagnosis

As ASPED is not a serious condition, prenatal diagnosis is not offered.

Genetic counseling

ASPED is transmitted as an autosomal dominant condition and genetic counseling is possible. Clinical variability and low penetrance have been reported.

Management and treatment

Treatment may involve orthopedic management (i.e. hip arthroplasty), and plastic surgery (when thumb involvement is very severe or if syndactyly is associated). In patients with severe hip involvement, walking aids may be required. Dental anomalies may require orthodontic management.

Prognosis

ASPED does not affect life-expectancy and the prognosis is good. Quality of life is reduced in those with untreated and severe coxarthrosis.