Hernias, Joint Rigidity, Skeletal Alterations Among First Signs of MPS, Study Finds

Hernias, flat feet, joint rigidity, and keen misalignment are among the clinical symptoms at diagnosis in patients with mucopolysaccharoidosis (MPS) including Sanfilippo syndrome, according to Mexican study.

The research, “Diagnosis of Mucopolysaccharidosis Based on History and Clinical Features: Evidence from the Bajio Region of Mexico,” was published in the journal Cureus.

Sanfilippo syndrome is one of seven types of MPS, collectively characterized by deficiencies and/or malfunction of specific enzymes responsible for breaking down large complex sugar molecules, called glycosaminoglycans (GAGs), leading to the formation and accumulation of toxic deposits in cells and tissues from different parts of the body.

Specific GAGs build-up in different organs, such as the eye’s cornea, skeleton, heart and central nervous system (brain and spinal cord).

Following clinical and radiographic evaluations, a dry peripheral blood spot test to determine enzyme activity is preformed to confirm diagnosis. If positive, the results need to be validated by measuring enzymatic serum activity or by a genetic analysis.

Early treatment with enzyme replacement therapy helps lower cellular GAG load and improves lung and heart function, as well as growth rate. However, the scarce literature on common characteristics of these diseases limits how early their diagnosis can be made.

For this study, researchers described the clinical and radiographic features of MPS patients in hospitals of Guanajuato, Mexico, from January to December 2016. Their analysis included 18 patients.

Seven patients had Morquio A syndrome (MPS IV-A), four Hurler syndrome (MPS I), three Sanfilippo syndrome (MPS III), two had Hunter syndrome (MPS II), and another two Maroteaux-Lamy syndrome (MPS VI).

The first disease-related manifestation occurred at 3.1 years on average (range: birth to nine years). The earliest was intrauterine pneumonia in an MPS I patient and the latest was knee valgus, or medial knee displacement, in a nine-year-old with MPS VI.

Genu valgus, a knee misalignment that turns the knees inward, was the most common alteration at diagnosis, in 14 patients (77%). Four of these cases were severe (all Morquio A syndrome), two were moderate — Maroteaux-Lamy syndrome – and the others were mild.

Additional first manifestations included hernia — umbilical (abdominal) or inguinal (groin) — in five patients, deformity in the thoracic cage (kyphosis or scoliosis) in three patients, joint rigidity, flat feet, and short stature.

The average time from the first symptom to accurate diagnosis was 2.7 years, with the range being between one month and six years. In turn, the average age at diagnosis was 5.6 years — range from one month to 15 years.

All patients showed dimorphism and relative macroglossia (unusually large tongue). Fifteen patients had a triangular dorsal hump in the nose. Other physical characteristics included hepatosplenomegaly (enlarged liver and spleen) in 15 patients, flat feet in 15 patients, hernia in 12, corneal opacity in 10, and dental diastasis (gap between teeth) in 16 patients.

All but one patient had a history of frequent respiratory infections, with two patients dying of subsequent complications. Half had a family history of this type of diseases, and six patients (33%) had consanguineous parents (blood-related).

Radiographic studies revealed that 15 patients (83.3%) shared at least two characteristics, including odontoid hypoplasia (incomplete development of a bone protuberance in the second cervical vertebra), atlantoaxial subluxation (a cervical spinal disorder causing impaired rotation of the neck), widened femoral necks (the weakest part of the femur bone), short ulna (one of the bones in the forearm), widened anterior ribs, pectus carinatum (protrusion of the sternum and ribs), and coxa valga (hip deformity with increased angled between the femoral neck and femoral shaft).

No patient with Sanfilippo syndrome had radiological alterations. All patients with Morquio A syndrome underwent orthopedic surgeries at the time of the study.

“Greater familiarity with these diseases is necessary in first-contact physicians in order to improve the detection and decrease the complications of disease progression,” researchers wrote.

Among the study’s limitations, researchers mentioned the small sample size and having patients from only one geographical area.