What is BACM?

Patient Presentation
A 7-year-old female came to clinic with a history of sudden onset of lower leg pain in the afternoon. She had stayed home the past few days because of an influenza-like illness and had been improving. After a short nap she woke up and complained that her calf muscles hurt and she was crying. She would walk but this also increased the pain. Her mother tried to massage her legs but this made the pain worse. The mother put her in a warm bath and used warm compresses that helped the child some. In clinic about 4 hours after the onset of the symptoms, the mother said that she thought it was very strange because as they were getting ready to come to the office, her pain had gone away. She was walking normally and now denied any pain. Both mother and daughter said that the change was quite dramatic. She had no bowel or bladder problems and her urine continued to be a normal color and amount. She denied any neurological problems including any changes in sensation or mentation. She denied any pain elsewhere in her body. The patient had not traveled and influenza was circulating in the community. The past medical history was positive for pressure equalizing ear tubes at age 3. The family history was negative for any muscle, neurological or kidney disease. The review of systems was positive for rhinorrhea and cough that were both improving. Her last fever was 2 days previous.

The physical examination showed a normal appearing female in no distress. Vital signs were normal including growth parameters of ~75%. HEENT showed clear rhinorrhea. Lungs were clear and abdomen was soft. Palpation of the lower extremities was normal. Vigorous dorsiflexion of the foot did not elicit pain. There was normal range of motion in all lower extremity joints including the toes. No warmth, redness, or swelling was noted. Strength and tone were normal. DTRs were +2/+2 with down going Babinski reflexes bilaterally. There were normal pulses and sensation in the lower extremities. The patient had a normal gait. Her back also had normal range of motion and did not elicit any pain.

The diagnosis of a transient acute myositis was made. The family was counseled that this can occur at times usually due to viruses. They were to continue to monitor her and make sure she kept hydrated. They were also to monitor her urine output and report if there were any changes in the quantity or coloring. “Usually as the virus goes away, so do the muscle pains, but you keep watching her closely and call if things change,” the pediatrician counseled.

Leg pain in children has a broad differential diagnosis and includes more innocuous problems such as growing pains and transient synovitis but also more serious problems including neurological diseases or malignancy. Occult or self-limited trauma are also common causes. A review can be found here. Limping can be painful or painless and has its own differential diagnosis which can overlap with leg pain. A differential diagnosis for limping can be found here. Muscle weakness also has its’ own differential diagnosis which can be found here.

Learning Point
Benign acute childhood myositis (BACM) has other names including viral myositis, acute myositis, influenza-induced myositis, or myalgia cruris eidemica. It is a benign acute myositis that occurs usually during the late winter or early springtime. School age children predominate but the range is ~3-14 years, with males being more common than females. Exact incidence as well as the exact disease mechanism are unknown.

Infectious agents that have been linked to it include influenza A (including H1N1), influenza B (most common overall), adenovirus, coxsackie, dengue, parainfluenza type 1, respiratory syncytial virus and Mycoplasma pneumoniae. The clinical course is that the patient has a viral prodrome for several days and the fever resolves. The patient then has sudden onset of lower extremity (particularly calf muscles) moderate to severe pain with refusal to walk/bear weight. The onset is often after a rest period such as a nap. Patients who are walking will try to minimize the muscle movement and may toe-walk or have a wide-based, stiff-legged gait (i.e. “Frankenstein gait”).

Physical examination shows pain usually in the gastronemius-soleus muscle groups, however rarely other groups can be involved predominantly in the lower extremities and very rarely in the upper extremities. The patient has normal strength, tone, deep tendon reflexes and normal neurological examination including sensory examination of the lower extremities. Laboratory testing is usually not needed but there is an elevated serum creatinine kinase level. Creatinine kinase level does not correlate with symptoms. There may also be elevated aspartate aminotransferase and alanine aminotransferase levels as well as leukopenia.

BACM is benign but Guillain-Barré, osteomyelitis and deep vein thrombosis may present acutely too. Rhabdomyolysis is also a rare complication of BACM and can be reviewed here. Compartment syndrome should be considered in the proper context also. Other problems such as dermatomyositis and muscular dystrophy usually have more chronic symptoms. Polio has not been eradicated from the world and with the appropriate history such as travel to Pakistan, Afghanistan or Nigeria, should also be a consideration.

The natural history of BACM is self-limited with resolution in about 1 week without sequelae. Recurrences are rare. Patients should be treated symptomatically.

Questions for Further Discussion
1. What are indications for a muscle biopsy?
2. What are indications for admission for leg pain?

3. What are indications for radiological imaging for leg pain?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at SearchingPediatrics.com, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for these topics: Myositis and Muscle Disorders.

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

Jain S, Kolber MR. A stiff-legged gait: benign acute childhood myositis. CMAJ. 2009 Nov 10;181(10):711-3.

Terlizzi V, Improta F, Raia V. Simple diagnosis of benign acute childhood myositis: Lessons from a case report. J Pediatr Neurosci. 2014 Sep-Dec;9(3):280-2.

Rosenberg T, Heitner S, Scolnik D, Levin Ben-Adiva E, Rimon A, Glatstein M. Outcome of Benign Acute Childhood Myositis: The Experience of 2 Large Tertiary Care Pediatric Hospitals. Pediatr Emerg Care. 2016 Aug 20. pp. 1-3.

Cavagnaro S M F, Aird G A, Harwardt R I, Marambio Q CG. Benign acute childhood myositis: Clinical series and literature review. Rev Chil Pediatr. 2017 Apr;88(2):268-274.

Magee H, Goldman RD. Viral myositis in children. Can Fam Physician. 2017 May;63(5):365-368.

Szenborn L, Toczek-Kubicka K, Zaryczanski J, Marchewka-Kowalik M, Miskiewicz K, Kuchar E. Benign Acute Childhood Myositis During Influenza B Outbreak. Adv Exp Med Biol. 2018;1039:29-34.

Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa

His Tooth is Funny Looking. What is It?

Patient Presentation
A 9-month-old male came to clinic for his well child examination. He was developmentally appropriate and was gaining good weight and height. His mother’s concern was that he had a tooth that looked abnormal to her. “He’s got 3 teeth but one of them looks longer than it should be,” she said.

The pertinent physical exam showed a well-appearing male with growth parameters in the 25-90% and tracking. His physical examination was normal except for his dentitia. His left mandibular central incisor and lateral incisor appeared normal. Where the right mandibular central and lateral incisor would be appeared to have 1 tooth. There was a slightly deeper indentation in the center of the tooth. All 3 teeth were not loose and the soft tissue surrounding them was normal. The coloration of the teeth was consistent across all the teeth and appeared normal. The eruption level of the all the teeth was symmetric.

The diagnosis of a healthy male with an abnormal tooth was made. A pediatric dental resident was rotating in the clinic and he diagnosed the patient with a single tooth that was most likely a fused tooth. “It can be hard to tell if it is a fusion or a germination problem at this point because he has so few teeth, but it looks healthy and normal. Some people call these double teeth,” he stated. “There’s nothing specifically we have to do now and mom can just do his regular oral care. I’m excited because the mom wants to bring him to see us in our dental clinic so I set up an appointment and I will get to see him again,” he said.

Teeth are specialized anatomic parts of the human body that are developed between the ectoderm and ecomesenchyme in a complex process called odontogenesis. More than 300 genes have been identified that influence odontogenesis. Dental abnormalities can have significance for cosmesis, malocclusion, dental caries and periodontal diseases. It is not uncommon for more than 1 area to be affected. For example, Hutchinson teeth which are caused by congenital syphilis are smaller with wider spacing between the teeth within the arch, and also have a characteristic notching.

Learning Point
Some common dental problems that may be seen or heard about by pediatricians include:

  • Tooth eruption
    • Ankylosis
    • Natal teeth
      • Usually prematurely erupted primary teeth that are present at birth
      • Neonatal teeth erupt in first month
      • Usually lower incisors (85%) and maxillary incisors (11%)
  • Developmental issues
    • Number
      • Anodontia
        • No teeth
      • Hypodontia
        • 1 or more fewer teeth
        • Common, usually in permanent dentitia
        • Etiology – genetic and includes:
          • Albright hereditary osteodystrophy
          • Crouzon’s syndrome
          • Down syndrome
          • Ectodermal dysplasia
          • Ellis-van Creveld
          • Hallermann-Streiff
          • Incontinentia pigmenti
      • Hyperdontia
        • Increased number of teeth
        • More common in permanent teeth especially maxillary incisors
        • Etiology includes:
          • Apert syndrome
          • Cleidocranial dysplasia
          • Craniometaphyseal dysplasia
          • Oral-Facial-Digital
    • Size
      • Microdontia
        • Smaller teeth than usual, generally uncommon
        • Maxillary lateral incisors and molars
        • Etiology includes:
          • Down syndrome
          • Pituitary dwarfism
      • Macrodontia
        • Larger teeth than usual
        • Etiology includes:
          • Hemifacial hyperplasia
          • Pituitary gigantism
    • Shape
      • Germination
        • Formation of two teeth from same follicle with evidence that separation was attempted
        • Often in maxillary anterior region
        • Etiology unknown
      • Fusion
        • Union of enamel and dentin in two or more separate developing teeth
        • Occurs more often in deciduous teeth
        • Etiology unknown

        Note: Germination and fusion problems may look very similar. Each has one joined/enlarged tooth, but the total tooth count is normal in germination defects and is one less in fusion defects when the anomalous tooth is counted as 1 tooth.

      • Concrescence
        • Two adjacent teeth unionized by cementum alone; dentin and roots are separated
        • Frequent in posterior maxillary teeth
        • Etiology is thought to be spacing issues, trauma, increased pressure or infection
      • Dens evaginatus
        • Cusp-like elevation in the central groove
        • Etiology – multifactorial
      • Dens invaginatus
        • Deep surface invagination of the crown lined by enamel
        • Maxilla and maxillary lateral incisors
        • Etiologies that are thought to be causal include:
          • Infection
          • Occlusal pressure
          • Trauma or pressure thought to be causal
      • Dilaceration
        • Abnormal angulation of the root relative to the crown
        • Can occur in all teeth
        • Etiology includes:
          • Axenfeld-Rieger syndrome
          • Ehlers-Danlos syndrome
          • Ichyosis, congenital
          • Smith Magenis syndrome
          • Trauma
      • Enamel pearls
        • Ectopic enamel globule(s) attached to the root
        • Maxillary molars are commonly affected
        • Cause abnormalities of enamel formation
      • Peg shaped laterals
        • Conical, undersized, tapered maxillary lateral incisor
        • Etiology – genetics and endocrine problems
      • Taurodontism
        • Body and pulp chamber are displaced apically in a multirooted tooth such that the pulp chamber is larger
        • Molars are commonly affected
        • Etiology includes:
          • Down syndrome
          • Ectodermal dysplasia
          • Kleinfelter’s syndrome
          • Mohr syndrome
          • Orofacial digital syndrome
          • Trichondento osseous syndrome
      • Talon cusp
        • Extra surface cusp
        • Most occurs in permanent dentitia in the maxilla mainly
      • Structure
        • Enamel abnormalities – amelogensis imperfecta
        • Dentin abnormalities – dentinogenesis imperfect
        • Multiple structural abnormalities – regional odontodysplasia
  • Enamel hypocalcification
    • Fluorosis
    • Infection
    • Inherited diseases
    • Medications
    • Metabolic disorders
    • Malnutrition
    • Rickets
    • Birth-related trauma
  • Post-developmental tooth loss
    • Trauma
    • Erosion – bulimia
    • Internal or external resorption
  • Environmental discoloration or staining – a review can be found here.

    Questions for Further Discussion
    1. What are indications for referral to a dentist?
    2. When is the recommended age for the first dental visit for children?
    3. At what age do primary dentitia erupt?

    Related Cases

    To Learn More
    To view pediatric review articles on this topic from the past year check PubMed.

    Evidence-based medicine information on this topic can be found at SearchingPediatrics.com, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

    Information prescriptions for patients can be found at MedlinePlus for these topics: Tooth Disorders and Child Dental Health.

    To view current news articles on this topic check Google News.

    To view images related to this topic check Google Images.

    To view videos related to this topic check YouTube Videos.

    Shrestha A, Marla V, Shrestha S, Maharjan IK. Chussid S. Developmental Anomalies Affecting the Morphology of Teeth – A Review. RSBP 2015:12(1)68-78.

    Chussid S. Abnormalities of Teeth.
    Available from the Internet at http://www.columbia.edu/itc/hs/dental/d7710/client_edit/dental_anomalies.pdf (cited 2/27/18).

    Donna M. D’Alessandro, MD
    Professor of Pediatrics, University of Iowa

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