► [Bone resorption of multiple phalangeal tufts]
Bone destruction at the terminal phalanges occurs in a variety of congenital and acquired disorders. Common causes of acquired bone resorption include several vascular (arteriosclerosis obliterans, diabetic gangrene,Raynaud disease), inflammatory (psoriatic and rheumatoid arthritis, scleroderma, dermato-myositis), neuropathic (diabetes, leprosy, tabes dor-salis, syringomelia, etc.), metabolic (hyperparathyroidism), infectious, and traumatic diseases. Thermal injury, electrical burns, and frostbite can also lead to multiple ungual tuftal resorption. In addition, there is a heterogeneous group of idiopathic disorders in which acro-osteolysis occurs, either as the cardinal clinical manifestation or in the context of a more widespread osteolytic process. Finally, a number of syndromes are associated with acro-osteolysis of the hands and feet. The clinical findings vary with the etiology, and the radiographic manifestations are nonspecific in many cases. Brachydactyly, digital contractures and progressive deformities can occur as late manifestations.
This section summarizes the clinical and radiographic characteristics of some of these disorders with multiple phalangeal tuft involvement. The situations in which acro-osteolysis is confined to one digit (benign or malignant neoplasms, infection, subungual exostosis, etc.) are not set out here.
Occupational acro-osteolysis is an occupational health hazard related to the inhalation of agents involved in the polymerization of vinyl chloride monomer, a plastic resin (Harris and Adams 1967; Ross 1970). After a variable period of latency characterized by easy fatigability, asthenia, nervousness and insomnia the typical symptoms appear. A Raynaud phenomenon-like disorder, with digital pain, numbness, and itching, is usually a premonitory sign indi cating that alterations in bone will probably ensue. Changes in the fingers and nails are usually apparent. Scleroderma-like skin plaques, soft tissue nodules, hyperhidrosis, skin discoloration, and carpal tunnel syndrome are additional clinical manifestations (Sadick 1976). Systemic involvement of variable degree is frequent, manifesting with hepatic fibrosis or angiosarcoma of the liver, splenomegaly, portal hypertension, thrombocytopenia, and pulmonary fibrosis (Binns 1979; Lewis 1999; Berk et al. 1976). The radiographic hallmark of the disease is osteoly-sis predominantly affecting the terminal phalanges of the hands (Fig. 6.63 a,b). However, other phalanges, the sacroiliac joints, and the feet may be involved, while the remainder of the skeleton is usually spared (Dodson et al. 1971; Jayson et al. 1976). Bandlike radiolucent areas of bone resorption are seen across the waist of one or more terminal phalanges, associated with varying degrees of tuftal fragmentation and resorption. Changes are usually more prominent in the thumb. At the sacroiliac joints, the bone changes are dominated by sclerosis similar to that encountered in the seronegative spondy-loarthropathies (Resnick and Niwayama 1995). If exposure is discontinued, partial repair of the osseous changes occurs, although finger shortening and clubbing usually persist as permanent damage. The pathophysiology of the disease is not known. Organic vascular lesions, such as narrowing and segmen-tary occlusions of digital arterioles and capillaries, probably due to a toxic chemical substance acting either directly on the walls of the vessels or through the central or peripheral nervous system, are major determinants (Falappa et al. 1982; Gama and Meira 1978). However, the lack of correlation between the severity of the osteolysis and the degree or duration of the exposure, plus the inconstant association between the Raynaud phenomenon and osteolysis, suggest that host factors might be important in the clinical expression of the disease (Resnick and Niwayama 1995). The radiographic appearance of the phalangeal changes in this condition may be indistinguishable from those of hyperparathyroidism, abnormal and prolonged stress, exposure to snake poison, and some of the familial disorders discussed below.
Hajdu-Cheney syndrome (acro-osteolysis with osteoporosis and changes in skull and mandible, OMIM 102500) is a connective tissue disorder characterized by acro-osteolysis, multiple wormian bones, and hypoplasia of the ramus of the mandible (Hajdu and Kauntze 1948; Cheney 1965). Short stature, generalized osteoporosis,bathrocephaly with
basilar impression and hydrocephalus, early loss of teeth, joint laxity, and kyphoscoliosis are features associated to varying degrees (Herrmann et al. 1973; Ades et al. 1993). The inheritance pattern is autosomal dominant, with the sporadic cases probably representing a fresh gene mutation. Changes in the phalanges, consisting of tuftal resorption and bandlike areas of lucency, are more severe in the hands than in the feet and may be indistinguishable from those of occupational exposure to vinyl chloride and pykn-odysostosis (OMIM 265800), a recessive disorderwith osteosclerosis. Whether these changes are related to destruction of bone already formed, possibly induced by local release of osteolytic mediators (Elias et al. 1978; Udell et al. 1986), or result from defective development of bone ('pseudo-osteolysis') (Herrmann et al. 1973) is controversial. Bone resorption also can be apparent in the mandibular rami, tubular bones, acromioclavicular joints and tarsal/metatarsal bones. Multiple fractures involving the long bones and the spine are frequent and are related to osteope-nia. Bone collapse at the craniocervical junction, together with basilar impression, can be life threatening. Cystic changes in the kidneys similar to those of autosomal dominant polycystic kidney disease (OMIM 173900) are an important component of the disorder in some cases (Kaplan et al. 1995). The face is dysmorphic with prominent maxilla, small mandible with diminished ramus, broad nose, low-set ears with prominent lobes, hypertelorism, and downward sloping eyes with narrow palpebral fissures (O'Reilly and Shaw 1994). The number and severity of the clinical manifestations vary widely. However, renal abnormalities tend to predominate during infancy, and multiple fractures and recurrent infections in early childhood, while neurological symptoms and joint abnormalities are usually manifestations of adulthood (Brennan and Pauli 2001). In
Fig. 6.63 a, b. Occupational acro-osteolysis. a Note bandlike resorption of the terminal phalanges of two digits, isolating small osseous fragments in the terminal tufts (arrows). Observe that the distal inter-phalangeal joints are intact. b In the thumb, involvement is particulary prominent. The proximal portion of the terminal phalanx is tapered and small bony foci (arrow) are located distally. (Reprinted with permission, from Resnick and Niwayama 1995)
the autosomal dominant acro-osteolysis of Schinz (OMIM 102400), slowly progressive osteolysis of the phalanges of the hands and feet with onset in the 2nd decade of life is associated with recurrent ulcers of the fingers and soles in the absence of neurological abnormalities. Healing occurs with loss of fingers or toes (Schinz et al. 1951). Unlike Hajdu-Cheney syndrome, this disorder involves no other obvious changes in the skull or long bones (Lamy and Maroteaux 1961). Again, the phenotype is similar to that exhibited by people engaged in the polymerization of vinyl chloride. An apparently autosomal recessive form of distal osteolysis (OMIM 259610), with onset in childhood and rapid progression of resorp-tive processes in subsequent years, has been described in the son and daughter of unaffected consanguineous parents (Petit and Fryns 1986). Severe destruction of the distal and middle phalanges of all fingers and toes is associated with short stature, mental retardation, and characteristic facies (maxillary hypoplasia, relative exophthalmos, and broad nasal tip). Neurological examination is normal.
In contrast to the aforementioned disorders, there is a group of idiopathic acro-osteolyses displaying signs of neuropathy. One such example is neurogenic acro-osteolysis (Giaccai type acroosteolysis, OMIM 201300), an autosomal recessive disorder characterized by progressive peripheral bone destruction, with osteolysis of phalanges of the hands and feet and skin ulceration (Giaccai 1952). Profuse hyper-hidrosis of the hands and feet and thickening of soft tissues around the knees and ankles are characteristic (Sirinavin et al. 1982). The abnormality resides in the peripheral sensory nerves and affects all modalities of sensation, with preservation of the motor and autonomic function. The manifestations are predominantly distal, with late involvement of the trunk. Loss of pain perception leads to erosions, ulcers,
osteomyelitis and, ultimately, extensive damage to the fingers and joints (Sirinavin et al. 1982; Bockers et al. 1989). The disorder begins in early childhood and is slowly progressive. There is some uncertainty as to whether the radicular neuropathy is due to failure of sensory nerve formation or to sensory nerve degeneration (Murray 1973). Unlike the situation in congenital indifference to pain (OMIM 147430,243000), in neurogenic acro-osteolysis the perception not only of pain but also of temperature and touch is compromised to varying degrees, whereas sensation is well preserved in proximal sites. Generalized osteoporosis and skull wormian bones are features this condition has in common with the Cheney syn-drome,but the pattern of inheritance is clearly different in the two disorders (autosomal recessive in neu-rogenic neuropathy and autosomal dominant in Cheney syndrome). The presence of hyperhidrosis of the hands and feet differentiates this disorder unmistakably from congenital sensory neuropathy with anhidrosis (OMIM 256800), another condition that involves acro-osteolysis (Fig. 6.64). A phenotypically related entity, hereditary sensory radicular neuropathy (OMIM 162400), is transmitted as an autosomal dominant trait (the gene responsible maps to chromosome 9q22) (Blai et al. 1998). This disorder is characterized by perforating ulcers of the feet, shooting pains in various parts of the body, and deafness manifesting during adulthood (i. e.,at a later age than in neurogenic acro-osteolysis) (Denny-Brown 1951). Acro-osteolysis, especially in the feet, can be a complication of repeated soft tissue ulcerations.
Acro-osteolysis also occurs in association with several dermatological disorders. The autosomal recessive Haim-Munk syndrome (OMIM 245010), a disorder that can be caused by mutations in the gene encoding cathepsin C at chromosomal location 11q14.1-q14.3 (Hart et al. 2000), is an association of congenital hyperkeratosis palmoplantaris, flat feet, onychogryphosis, periodontal pathology, arachn-odactyly, and acro-osteolysis (Haim and Munk 1965). The disorder is similar to but distinct from Papillon-Lefevre syndrome (OMIM 245000), which is also caused by mutations in the cathepsin C gene. Features common to both are severe periodontitis with early loss of teeth, palmoplantar keratosis, and autosomal recessive inheritance. Distinguishing features include calcification of dura mater and increased susceptibility to infections in the Papillon-Lefevre syndrome and arachnodactyly, acro-osteolysis, and onychogryphosis in the Haim-Munk syndrome (Hart et al. 1997).
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