HAND ARTHROPATHY: A CLUE TO THE DIAGNOSIS OF THE KNIEST (SWISS CHEESE CARTILAGE) DYSPLASIA

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1 Rheumatology and Rehabilitation, 1980,19, HAND ARTHROPATHY: A CLUE TO THE DIAGNOSIS OF THE KNIEST (SWISS CHEESE CARTILAGE) DYSPLASIA BY RIDA A. FRAYHA 1, HUSN FRAYHA 2 AND RAFIC MELHEM 3 The Departments of 1 Internal Medicine, 'Pediatrics and ^Radiology, American University Medical Center, Beirut, Lebanon SUMMARY Two patients with the rare dystrophy of Kniest (Swiss cheese cartilage syndrome) are reported. A salient clinicoradiological diagnostic feature is an arthropathy of the hands. THE Kniest dysplasia, thus far described in 16 patients (Kniest, 1952; Maroteaux and Spranger, 1973; Rimoin et al., 1973a; Spranger and Maroteaux, 1974; Lachman et al., 1975; Frayha et al., 1979), is a chondrodystrophy with characteristic clinical, roentgenographic, and chondrosseous histopathological findings. A triad of disproportionate dwarfism with kyphoscoliosis, a peculiar round and flattened facies, and deformed extremities with articular enlargements has been described in most of the cases. Other features include high arched palate, myopia, and hearing loss. Both sexes are affected equally and all cases have been sporadic, with the exception that one case of transmission from mother to son has been reported (Maroteaux and Spranger, 1973) favouring autosomal dominant inheritance. Shortened tubular bones with metaphyseal flaring, epiphyseal delay, and platyspondylitis with vertebral irregularity constitute classical radiological findings. Some areas of the cartilage show large chondrocytes surrounded by very loosely woven matrix with empty spaces. The appearance has been likened to Swiss cheese. This appearance is possibly unique for this disorder. The growth plate contains broad and short spicules of calcified cartilage and bone resulting from its hypercellularity in a relatively loose matrix. These specific abnormalities in the structure of cartilage have suggested a defect in the organization of cartilage collagens (Rimoin et al., 19736; Lachman et al., 1975). Two patients with the Kniest dysplasia were evaluated rheumatologically and it was noticed that a distinct polyarthropathy characterizes the syndrome. This unique arthropathy most pronounced over the hands appears to be a clue to the diagnosis. Case reports 1. M.S., a nine-year-old boy, reported in detail elsewhere (Frayha et al., 1979), presented with unusual stature and articular contractures. At the age of seven, painless symmetrical knobby enlargements of the minor joints of both hands were noticed. Examination revealed disproportionate dwarfism (Fig. 1, Plate XIII), dorsal kyphosis, flattened and rounded face with prominent eyes and broad mouth, high arched palate, unilateral ptosis of eyelid, and neurosensory hearing loss. Examination of the joints demonstrated remarkably symmetrical non-inflammatory bony enlargements of the articular structures resulting in a characteristic knobby appearance. These changes were more evident over the proximal interphalangeal joints Accepted for publication January Requests for reprints to Dr. R. A. Frayha, Department of Internal Medicine, American University of Beirut, Lebanon. 167

2 168 RHEUMATOLOGY AND REHABILITATION VOL. XIX NO. 3 (PIP), elbows, and knees. The mobility of the PIP and DIP joints was markedly reduced. The hips, knees and elbows were held infixedflexion contractures. Radiological studies, similar to those described in case 2, confirmed the diagnosis of the Kniest dysplasia. 2. R.A., a six-year-old girl born to non-consanguinous parents, was referred to us with the diagnosis of juvenile rheumatoid arthritis (JRA). She was so diagnosed two years earlier on the basis of deformed digits and was put on salicylates although at no time did she experience articular pains, soft-tissue swellings, or stiffness on inactivation. She could walk at the age of 10 months and her intelligence was normal for her age. At the age of four, her parents noticed progressive enlargements of the digits, resulting in inability to form a fist. A prominent feature on physical examination was the disproportionate dwarfism; the height was 111 cm and the chest was barrel-shaped. The face was rounded with prominent eyes, broad mouth, high arched palate and a flat, wide nasal bridge. Ophthalmologic and audiometric examinations were normal. No organomegaly was detected and the cardiovascular and neurological examinations were unremarkable. Her two younger siblings were normal. Musculoskeletal examination A gross finding was symmetrical bony growths involving all the PIP and DIP joints, more pronounced over the PIP, in particular the second and third joints. These bone-hard articular enlargements, affecting the medial, lateral, and dorsal aspects of each joint, were not associated with an overlying synovial reaction; all inflammatory signs and symptoms were absent. The joints moved freely with no evidence of crepitations or ankyloses. The fingers looked elongated and, with the interphalangeal articular enlargements, gave the hand a characteristic knobby appearance (Fig. 2, Plate XIV). Although there were no fixed contractures, the ability to form a fist was slightly impaired. Bilateral knock-knee deformities were present with 20 flexion contractures. The hips had normal range of motion and the feet wereflatand turned out. Laboratory evaluation The haemogram, erythrocyte sedimentation rate, routine chemistry, RA latex fixation, and urinalysis were normal or negative. Quantitative 24-hour urinary excretion of mucopolysaccharides (DiFerrante and Rich, 1956) was normal. A survey of the whole skeleton showed diffuse anomalies of the axial and appendicular bones consisting of generalized platyspondyly most marked at the dorsolumbar junction. A mild knock-knee deformity with irregularity and fragmentation of the proximal epiphyses of both tibiae and the distal epiphyses of the humeri and the heads of the radii. The hands showed the typical changes of the Kniest dysplasia (Fig. 3, Plate XIV): the metaphyses were shortened with squaring of the distal ends of the phalanges which appeared wider than normal, the middle and the distal phalanges were short and wide, the ossification centres were malformed and the joint spaces were narrowed. The feet showed similar though milder changes than those of the hands. DISCUSSION The newly defined chondrodysplasia of Kniest may superficially simulate JRA, mucopolysaccharidoses, spondylo-epiphyseal dysplasia congenita or other dystrophies. These two patients were, in fact, erroneously labelled as JRA and put on salicylates despite the fact that neither had suffered from articular pains or swellings. Furthermore, the erythrocyte sedimentation rate had remained normal. The non-inflammatory aspect of the disease should be emphasized and this, along with the clinical triad of disproportionate dwarfism, enlarged joints, and the characteristic facies, should lead to the diagnosis of this dysplasia. The gross appearance of the minor joints of the hands is unique for the Kniest dysplasia and could be a clue to its diagnosis. The hallmark of this arthropathy is the remarkably symmetrical bony growths at the interphalangeal levels resulting in knobby fingers (Frayha et al., 1979). Thus, the hand simulates that of an adult patient with degenerative joint disease and multiple Heberden's and Bouchard's nodes. The bony

3 PLATE XV FIG. 1. Patient M.S. Gross characteristic features include disproportionate dwarfism, barrel-shaped chest,flexioncontractures of elbows, hips, and knees, and a round face with prominent eyes and broad mouth. [facing page 168

4 PLATE XVI FIG. 2. Patient RA. The interphalangeal joints demonstrate symmetrical bone-hard knobby enlargements. Note the resemblance of the hand to that with degenerative joint disease. FIG. 3. Patient RA. The typical roentgenographic features of the Kniest dysplasia: the metaphyses are short and wide, the ossification centres are irregular and the joint spaces are narrowed.

5 FRAYHA ET AL.: HAND ARTHROPATHY 169 growths are more pronounced over the medial and lateral sides of each joint than over the dorsal aspect. Another characteristic clinical feature is the lack of inflammatory signs, in particular synovial thickening. The reduced mobility at the PIP and DIP levels results in gross functional impairment in the Kniest hand. Besides the involvement of the minor joints of the hands, other articular structures demonstrate non-painful symmetrical bulbous enlargements with fixed flexion contractural deformities contributing to the incapacitating nature of the disease. These changes were noticed over the elbows and knees of both of patients and over the hips in one. The limitation of motion in the weight-bearing joints of the lower extremities, together with the axial changes in the vertebral and pelvic structures, results in a waddling gait. Radiological studies of the hands are distinctive (Lachman et al., 1975; Frayha et al., 1979). Before the appearance of the epiphyseal centres in the phalanges and metacarpals, the hands look normal. However, at a later age, delayed epiphyseal ossification, generalized osteopenia with increased density at all the interphalangeal joints become evident. After the age of six, all joint spaces, including the intercarpals, become narrowed; the epiphyses, especially the metacarpals, become flattened on the side opposite the epiphyseal plate; and large malformed carpal centres are present. At 12 years of age, the bulbous enlargements of both ends of the bones are striking. Widening at the ends of the bones of the hands, fragmented accessory phalangeal centres, epiphyseal flattening in the metacarpals, narrowed joint spaces, together with platyspondyly, radiologically differentiate this syndrome from other skeletal dysplasias and arthropathies. Experience with these two patients indicates that the clinical and radiological features of the arthropathy are characteristic for the diagnosis of this chondrodysplasia. REFERENCES DIFERRANTE, N. and RICH, C. (1956) The determination of acid aminopolysaccharide in urine. J. Lab. Clin. Med. 48,491^. FRAYHA, R., MELHEM, R. and IDRISS, H. (1979) The Kniest (Swiss cheese cartilage) syndrome. Description of a distinct arthropathy. Arthritis Rheum. 22, KNIEST, W. (1952) Zur Abgrenzung der Dysostosis enchondralis von der Chondrodystrophie. Z. Kinderheilkd. 70,633^10. LACHMAN, R. S., RIMOIN, D. L., HOLLISTER, D. W., DORST, J., SIGGERS, D., MCALISTER, W., KAUFMAN, R. and LANGER, L. (1975) The Kniest syndrome. Am. J. Roentgenol. 123, MAROTEAUX, P. and SPRANGER, J. (1973) La maladie de Kniest. Arch. Fr. Pediatr. 30, RIMOIN, D. L., HOLLISTER, D. W., SILBERBERG, R., LACHMAN, R., MCALISTER, W. and KAUFMAN, R. (1973a) Kniest (Swiss cheese cartilage) syndrome: clinical, radiographic, histologic and ultra-structural studies. Clin. Res. 21,296. SIGGERS, D., SILBERBERG, R., LACHMAN, R. S., MCALISTER, W., KAUFMAN, R., MCKUSICK, V. and DORST, J. (19736) Clinical radiologic, histologic and ultrastructural definition of Kniest syndrome. Pediatr. Res. 7,348. SPRANGER, J. and MAROTEAUX, P. (1974) The Kniest syndrome. Birth Defects Original Article Series X (12),