Anthropometric characteristics of four Polish children with mucopolysaccharidosis

Background Mucopolysaccharidosis relates to a group of seven prevalent types of disorders that are categorized on the basis of specific enzyme deficiency or the major symptoms, or both. A typical clinical presentation includes such symptoms and characteristics as short stature, facial dysmorphism, skeletal deformities, pulmonary dysfunction, joint stiffness and contractures, myocardial hypertrophy, neurological symptoms, and mental retardation. Case presentation The purpose of this study was to perform a detailed anthropometric assessment in four cases of children with mucopolysaccharidosis (MPS) I and II types aged from 4 to 13 years from the Podkarpacie Province (south-eastern Poland). Anthropometric assessment included several parameters and indices related to body structure. All examined patients are characterized by severely disordered physical growth in comparison with the Polish norms presented in the reference charts. Conclusions Examined children with MPS are characterized by especially low values relating to longitudinal and transversal parameters of body build. Anthropometric data could be used in early diagnosis of MPS and assessment of results of its treatment.


Background
The term mucopolysaccharidosis (MPS) relates to a group of autosomal recessive metabolic disorders caused by the absence or dysfunction of the lysosomal enzymes involved in the degradation of glycosaminoglycals (GAGs). The MPS group comprises the seven prevalent types of disorder that are categorized on the basis of specific enzyme deficiency or the major clinical symptoms, or both [1]. A typical clinical presentation includes such symptoms and characteristics as short stature, facial dysmorphism, skeletal deformities, pulmonary dysfunction, joint stiffness and contractures, myocardial hypertrophy, neurological symptoms, and mental retardation. In most cases patients are symptomatic at the age of 2-4 years. Manifestation of the disease may be confused with other diseases such as inflammatory arthitides [2]. It should be mentioned that delays in diagnosis of MPS happen quite frequently and some children will suffer for some time with an unrecognized disorder. This kind of diseases are chronic and progressive even when they are treated or not. Some types of MPS are now treatable by means of enzyme replacement therapy and hematopoietic stem cell transplantation [3]. An important element of an exact assessment of the effects of treatment is the evaluation of the physical growth pattern in an individual patient. This kind of evaluation is based on anthropometric data.
The main study objective was to present and analyze selected anthropometric parameters and bodily proportions in four children with MPS I and II in order to highlight the distinctive manifestation of clinical symptoms of MPS in the dimension of physical development of the affected children. Results of the study may be used in the evaluation of the physical growth pattern of patients with MPS, its deviation in comparison with the reference charts and assessment of the effects of treatment.

Case presentation
The study population consisted of 4 cases of children (3 males with MPS II) and 1 female (with MPS I) aged from 4 to 13 years. They represented the population of children with MPS from the Podkarpacie Province (south-eastern Poland) diagnosed at the time of examination (i.e. in 2010). The examination took place at the Department of Pediatrics of the Provincial Hospital No. 2 in Rzeszow. The author was invited to perform anthropometric studies of the 4 children diagnosed with MPS who participated in a special pharmacological treatment project. Three boys with MPS II were treated with Elaprase, and in the case of one girl with MPS I (Scheie syndrome) Aldurazyme was applied. All the children came from a rural social environment ( Table 1). The anthropometric measurements were taking during an initial stage of the treatment programme. The following tools were used: anthropometric tape, physician scale, Martin anthropometer, and set of callipers (including skinfold calliper). All of them were used according to the standard anthropometric technique.
The examinations were based on the method of measurement and analysis of anthropometric parameters defined by Martin and Sailer [4]. Methodological principles recommended by the International Society for Advancement of Kinanthropometry were also followed [5]. On the basis of anthropometric data the following indexes of proportion were calculated: trunk length index, head and neck for height index, shoulder-height index, pelvic-height index, upper extremity length index, arm length index, inter-extremity index, lower extremity length index, shoulder breadth index, pelvic breadth index, hipto-shoulder index, global adiposity (sum of 3 skinfolds: triceps, subscapular, suprailiac), Body Mass Index (BMI), Rohrer index, head-to-chest circumference index, Marty's index of chest growth, arm muscles circumference index, cross-section area of arm (mm 2 ), cross-section area of arm muscles (mm 2 ), cross-section area of arm adipose tissue (mm 2 ), head breadth-to-length index, morphological face index, head-to-nose index. Obtained results were analyzed with reference to the Polish norms elaborated by Palczewska & Niedzwiecka [6].
The values of body height in each of the children examined are placed below 3rd centile, which means that they are low-statured (Table 2) Arm muscle circumference (AMC) in the children runs into values much lower than average (<25c). For example, the cross-sectional surface of arm adipose tissue records markedly higher values (>75c).
A short trunk is a distinct characteristic of all the boys with MPS II type, while the girl with MPS I has a relatively long trunk. Interpretation of the remaining indexes of proportion varies with each particular case. Nevertheless, MPS is a factor which should be taken into consideration during differentiation of the cause of a short stature.

Discussion
In the professional medical literature there is a lack of publications containing detailed anthropometric data  Similar studies were performed in other European countries, for example, in the Czech Republic and Slovakia [8]. The aim of the research cited was to describe the clinical symptoms, typical course and to evaluate the results of the treatment of 24 Czech and Slovak children with MPS I. Most of the patients had macrocephaly and skeletal changes, cardiomyopathy, hearing impairment, joint stiffness, and carpal tunnel syndrome. The authors emphasized the role of the advanced diagnosis, including the anthropometric parameters. Shah et al. [9] found in a 10year-old East-Asian boy with MPS such characteristics as an acrocephalic head, short stature, short neck and small stubby fingers with flexion of distal interphalangeal joint, and mild mental retardation. Other authors emphasize that ocular manifestations in MPS I and II may occur not only in the form of corneal clouding, but also include retinopathy, glaucoma, optic disc swelling, optic atrophy, ocular motility and refractive error problems [10].
In practice, the results of anthropometric measurements may be used in the diagnosis of some types of MPS. For example, the phenotype of MPS IVA can be classified into three subgroups according to the patient's final height: severe (<120 cm), intermediate (between 120 and 140 cm) and mild (above 140 cm), respectively [11]. The patients of the severe type are also characterized by features such as short stature, genu odontoid dysplasia, valgum, protrusion of the chest, kyphoscoliosis, hypermobility of joints and abnormal gait, and are mostly below the 90th percentile on the Morquio A growth charts. They often have the onset during infancy, and cannot survive through the second or third decade of life. The patients of the intermediate and mild types, generally called 'attenuated' types, have relatively less skeletal involvement and longer life span [12].
In the cases of our children the values of head breadth-to-length index have revealed three types of proportions: brachycephalic, hyperbrachycephalic and mesocephalic. There was no child with an acrocephalic or dolichocephalic head.
In the group of parameters relating to the process of body growth, special attention must be given to short stature, especially to low values characterizing the length of trunk, head and neck height, lower extremity length, and shoulder and hip breadth. Within the scope of indexes describing the process of differentiation of body proportions, the data obtained point to, in particular narrow shoulders (shoulder growth index), short-legs (relative lower extremity length), and a high level of chest growth (Marty's index).
Children with MPS are characterized by a higher degree of adiposity, which is evidenced by relatively high values of the parameters relating to global adiposity and the cross-sectional area of arm adipose tissue. Children with MPS also display a lower level of musculature development in comparison to their normal peers, as evidenced by the values referring to the cross-sectional area of arm muscles. The boys examined are characterized by a short trunk, whereas the girl is long-statured.