Developmental milestones

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Developmental milestones are tasks most children learn, or physical developments, that commonly appear in certain age ranges. For example:

• Ability to lift and control the orientation of the head (Neck control) is attained at about 3 months
• Crawling begins at about 7 months
• Walking unsupported is attained at about 12 months
• Speech begins
• Voice lowers in pitch (especially noticeable in boys)
• Pubic hair appears
• Genitals and reproductive organs mature
• Menses begin (females)
• Body hair and facial hair appears

"Normal" age ranges for many milestones are broad (a factor of 1.5 - 2 from bottom to top is possible). For this and other reasons, a single delayed milestone, especially task-related, is rarely in itself a basis for diagnosing a problem.

Note: the Tanner stages can be used to approximately judge a child's age based on physical development.

Note: the age ranges and the developmental milestones are based loosely on majority growth, implications of the majority can provide a wide variance to actual age.

Unfortunately, many cases of delayed milestones are difficult to diagonse. A recently discovered genetic disorder (discovered in 2004) caused by mutation in the transporter of Thyroid, MCT8, also known as SLC16A2, is believed to account for a significant fraction of undiagnosed cases of hypotonic/floppy infants with delayed milestones. This genetic defect was known as Allan-Herndon-Dudley Syndrome (since 1944) without knowing its actual cause. Some of the symptoms for this disorder as are follows: Normal to slightly elevated TSH, elevated T3 and reduced T4 (ratio of T3/T4 is about double its normal value). Normal looking at birth and for the first few years, hypotonic (floppy), in particular difficulty to hold the head, possibly difficulty to thrive, possibly with delayed myelination (if so, MRI pattern is similar to Pelizaeus-Merzbacher disease, known as PMD), possibly with decreased mitochondrial enzyme activities, possibly with fluctuating lactate level. Patients have an alert face, a limited IQ, patients may never talk/walk, 50% need feeding tube, patients have a normal life span. This disease can be ruled out with a simple TSH/T4/T3 thyroid test. Research is being done to find a treatment for this disease and Thyroid Hormone Therapy is known to help.

If you have a baby who is hypotonic/floppy with delayed milestones, please make sure your care giver gives priority to the new recommendations that the Thyroid tests should not be limited to TSH (common Thyroid test) and T3 and T4 should be also tested as the combination of these commonly available tests can rule out the possibility of MCT8.

See also

• Delayed puberty
• Mental retardation
• Delayed milestone

External links

• CDC's "Learn the Signs. Act Early.” campaign - Information for parents on early childhood development and developmental disabilities
• Developmental Milestones National Dissemination Center for Children with Disabilities (NICHCY)
• YourChild: Developmental Milestones University of Michigan Health System
• NIH
• March of Dimes
• http://www.ipaworld.org/res/Journals/PlayRights_v29n3_2007.pdf, page 3, Table 1: Mastery of Developmental Tasks -- Birth to 15 Months

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