Metachondromatosis: A Confusing Disease

Abstract

Metachondromatosis is a rare autosomal dominant genetic disease with incomplete penetrance that involves abnormal function of the PTPN11 gene. Differentiation between chondrogenic tumors is a challenge for orthopedists. We report a case of a 5 year-old girl with metachondromatosis, a disease that shares attributes with osteochondromas and enchondromas. We found multiple osteochondroma-like lesions with the atypical characteristic of guiding its growth toward the neighboring joint (epyphisis) instead of moving away from it. Furthermore, columnar enchondroma-like lesions were clearly visible in the right distal radius, in the proximal femoral cervix and in the iliac crests. The patient reported that some other tumor had disappeared or downsized with time. This case was debated between a multidisciplinary skeletal dysplasia group. The aforementioned clinical and radiographic findings reinforced the hypothetical diagnosis of metachondromatosis. Definitive diagnosis of metachondromatosis requires a combination of clinical, radiographical and histopathological findings. Differential diagnosis between enchondromas, osteochondromas and metachondromatosis is vital due to differences in malignization and natural history. When a patient has multiple enchondromas and osteochondromas with regression of some lesions and atypical radiographical characteristic of the osteochondroma-like lesions pointing toward the epiphysis, metachondromatosis, a rare disease, must be considered. Surgical treatment is reserved for painful lesions Risk of malignization is insignificant and genetic advice must be given due it is an autosomal dominant disease.

Keywords: bone neoplasms/pathology; child; enchondromas; exostoses, multiple hereditary; osteochondromas.

Fig. 1

Images of different histological sections stained with hematoxylin-eosin. A) Sample of the exostotic lesion constituted by a cartilaginous cap with an osteoid central trabecular matrix, 2.5X. B) The chondral matrix shows mature characteristics with endochondral ossification, 4X. C) Transition zone between the peripheral cartilaginous component and trabecular bone resembling a slightly disorganized growth plate, 4X. D) Chondrocytes are arranged in isogenic groups, larger in the central portion, without atypia or atypical mitoses, 10X.

Fig. 2

Anteroposterior view of both hands showing multiple osteochondroma-like lesions with the atypical characteristic of guiding their growth toward the neighboring joint (epyphisis) instead of moving away from it.

Fig. 3

Anteroposterior view of the pelvis. In metachondromatosis, enchondromas distribute mainly around the iliac crest and metaphyseal regions of the long bones.

Fig. 1

Imagens de diferentes seções histológicas coloridas com hematoxilina-eosina. A) Amostra da lesão exostótica constituída por uma capa cartilaginosa com uma matriz osteoide central trabecular, 2,5X. B) A matriz condral apresenta características maduras com ossificação endocondral, 4X.C) Zona de transição entre o componente cartilaginoso periférico e osso trabecular semelhante a uma placa de crescimento ligeiramente desorganizada, 4X. D) Os condrócitos são dispostos em grupos isogênicos, maiores na porção central, sem atipia ou mitoses atípicas, 10X.

Fig. 2

Visão anteroposterior de ambas as mãos mostrando múltiplas lesões semelhantes a osteocondroma com a característica atípica de guiar seu crescimento em direção à articulação vizinha (epífise) em vez de se afastar dela.

Fig. 3

Visão anteroposterior da pelve. Na metacondromatose, os encondromas se distribuem principalmente em torno da crista ilíaca e regiões metafisárias dos ossos longos.